PDA

View Full Version : DIY gantry crane



taydin
11-03-2012, 05:43 PM
Ok, finally got around doing the cad work for my DIY gantry crane. I would love to hear any feedback from the community about any issues or improvements.

http://www.taydin.org/web/vinc/scaled_vinc.png

http://www.taydin.org/web/vinc/scaled_vinc1.png

http://www.taydin.org/web/vinc/scaled_vinc2.png

http://www.taydin.org/web/vinc/scaled_vinc3.png

taydin
11-03-2012, 05:43 PM
http://www.taydin.org/web/vinc/scaled_vinc4.png

taydin
11-03-2012, 05:55 PM
I am going to use 140 x 66 mm I Beams for the parallel and cross rail. The posts are 100 x 100 x 5 mm square tubes. The post feet are going to be made from 150 x 15 mm steel. I know they don't need to be that thick, but I have lots of this stock laying around, might as well use them...

The wheels are going to be made out of some type of hard plastic, but I don't know what its scientific name is. There will be two bearings at each side of the wheel (6008N). The wheel diameter is 180 mm and the shaft is going to be 40mm diameter silver steel.

I used two plates for the post feet. There will be four M16 screws so I can align them.

According to beam stress calculations I made, the 6m long NPI140 I Beam that I use will deflect 9.5mm when loaded with 1 ton at the center. With 2 tons, the deflection is about 20mm.

My goal is to be able to lift 750 Kg, even though most of the time the load will be less than 100 Kg.

I got good feedback from an FEA expert, who recommended to use a safety factory of at least 4. According to some internet sites, the NPI140 has a static load capacity of around 3 tons. So it seems just the beam itself should be good for 750 Kg, what do you guys think?

darryl
11-03-2012, 06:19 PM
I'll be perfectly honest- I don't like the design at all. With this design, you'd be relying on welded joints to resist a lot of torquing and twisting, especially in the trolley area. I kind of like the idea of the angle iron to give a centering action to the wheels, but I think it would be better to just run plain wheels and ride them directly on top the I beams. Also I would sandwich the wheels between steel plates instead of having them outboard on stub axles. The 'cross beam' would extend past the I beams slightly, and one plate would be welded across the ends. The inner plate would be in two pieces, and a brace would be added across the bottom of those to tie those two plates together. All these plates would extend down past the side of the upper surface of the I beams to act as flanges. This is going to use less material and be much stronger at the same time. There's a lot less reliance on the welds having to resist tension forces.

I know this is a preliminary drawing, but I would consider adding some triangulation to both the cross beam and the side beams to help them resist deflection.

On the bottoms of your towers, it appears that the base plates are butt welded to make them larger. Maybe I'm misinterpreting this, but that's also something I would avoid, plus I would add diagonal bracing there. You can also use diagonal bracing where the towers meet the I beams, and you can tie those braces in with the triangular bracing on the main beams.

Where there are areas where you can't avoid a weld having to resist a direct tension force, the bracing structure can spread the load over multiple welds.

I'm not going to say anything at all about the safe loading of the beams. I'm presuming that either the material will be sized to suit, or the safe loading will be determined using proper math and engineering tables.

I will suggest one other thing though- in order for the trolley to travel the beams smoothly, you would want both ends of the cross beam to travel the identical distances at the same time. I would not rely on them doing this on their own. I have found that a cable and pulley system works well and reliably to eliminate the potential problems with 'cocking'. The cable system could also give you the means to drive the gantry either by hand or motorized.

taydin
11-03-2012, 06:42 PM
Darryl, thank you for the useful suggestions. Adding the diagonals to the top and bottom of the posts makes quite sense. When you say triangulation, I guess you are talking about welding 45 degree pieces inside of the I beam. The wheels of the lifting motor will run on the bottom of the I beam, so I need those areas to be free.

The base plates are indeed butt welded out of 150 x 15 mm plates that I have available. In order to use one piece 300 x 300 mm plates, I would have to find a place that will cut them for me from their stock.

The cocking is something that I am worried about, too. In the cable system you described, how are the pulleys on both ends synchronized? Using a 6m long shaft?

Barrington
11-03-2012, 07:02 PM
As I understand it, that is a 'bridge' crane and the rolling elements are termed 'endtrucks'. Googling those terms might turn up a few more ideas.

If you really don't need intermediate supports on the side rails, and you've got the height required, it might be simpler to use 'under running' endtrucks, perhaps assembled from common I-beam trolleys. (Self guiding and fairly easy to make if you don't want to buy anything ready made.)

A few useful drawings are linked to on this page http://www.cignys.com/conveyor_components/test_sub-page/bridge_crane_kits/ (http://www.cignys.com/conveyor_components/test_sub-page/bridge_crane_kits/)


Cheers


.

taydin
11-03-2012, 07:25 PM
Hello Barrington, thank you for the link. The 4 wheel trolleys travelling on the inside of the I beam make quite sense. Wondering if this arrangement will completely prevent the cocking that darryl was mentioning, hmm... Also, the products on this website use steel wheels. I chose plastic to get some dampening effect during travel. With steel wheel, every little bump on the rails will immediately be conveyed to the cross beam.

I need the cross beam to be at the same level as the rail beams, because of ceiling height limitation. But in any case, the same trolley running on the lower beam can be used. Only difference is the positioning of the cross beam on the trolley.

Tamper84
11-03-2012, 07:30 PM
http://www.garagejournal.com/forum/showthread.php?t=2122&page=2&highlight=bridge+crane look through this guys garage build thread. He built a 2 ton bridge crane. And he used flanged bearings for the wheels. Neat design, I would love to do this in mine as well. If this comes up on the first page, go to the 2 page of old car guys shop build. Page 2 and three he explains his crane.

HTH,
Chris

taydin
11-03-2012, 08:13 PM
http://www.garagejournal.com/forum/showthread.php?t=2122&page=2&highlight=bridge+crane look through this guys garage build thread. He built a 2 ton bridge crane.

Well, that's an eye opener! If that crane is 2 tons, then my crane is probably not safe for 750 Kg capacity. Another noteworthy property of his crane is that the cross beam is much beefier than the rails ... This doesn't make too much sense, though. If the 2 tons is moved at the edge of the cross beam, then almost all of the load will be on that side rail. Actually, it will be more than 2 tons, because part of the weight of the cross beam is also on that side rail. So that side rail must be safe for more than 2 tons. And if it is safe, why use a much larger cross beam?

SVS
11-03-2012, 08:28 PM
Use a "pantograph" cable system.

Let's say the crane travels North and South.

Mount two cable sheaves on a common vertical axle at each end of the beam.(two axles, four sheaves in total)

Anchor one cable in the NW corner, make a 1/4 turn at W end of crane, then another 1/4 turn at E end of crane then anchor with a turnbuckle in SE corner. (NW-W-E-SE)

Mirror image a second cable. (NE-E-W-SW)

Use the turnbuckles to equalize cable sag and regulate the crane.

That feels like a really ponderous explanation but hopefully you get the idea. My Dad is still using a crane he built with this system in 1977.

NzOldun
11-03-2012, 08:37 PM
Ok, finally got around doing the cad work for my DIY gantry crane. I would love to hear any feedback from the community about any issues or improvements.

http://www.taydin.org/web/vinc/scaled_vinc.png

http://www.taydin.org/web/vinc/scaled_vinc1.png

http://www.taydin.org/web/vinc/scaled_vinc2.png

http://www.taydin.org/web/vinc/scaled_vinc3.png

It may not matter in your location, but if the lifting is powered, it may come under a local or state statutory requirements.

The design of Overhead Travelling Cranes, (OHT cranes) is usually done in accordance with a given National Standard (think ASME, BSS et. al).

Usually, the deflection of the various beams is the controlling factor, not their strength. For instance, AFAICR, in BS 466, the maximum deflection of the main beam is limited to L/900, L being the down shop rail centres. I'm sure ASME has something similar.

Also the wheel centres on the end carriages look too short to effectively guard against 'crabbing'. They should be about 1/6th of the main beam span - again the standard will usually dictate this.

It is also usual to consider a load of about 10%, acting sideways to the main beam, at the same time as the vertical load, to allow for off-centre and/or swinging loads. For an underslung hoist unit, this introduces torsion into the main beam - and 'I' beams are notoriously unstable under torsional loads!

Finally, if, as I am, you are living in an earthquake prone region, you also have to have a margin for this phenomena!!

Gets interesting, doesn't it?

NzOldun

darryl
11-03-2012, 08:58 PM
Here's a layout of a cable control system.

http://img.photobucket.com/albums/v136/heinrich/cablelayout.jpg

There are six pulleys with the cable strung around as shown. The segments of the cable on the very outside of the pulleys (topmost and lowest in the image) move in the same direction anytime the cable is caused to move around the pulleys. You would attach a point on the gantry to the cable on either side. If one end of the gantry is moved, the cable pulls the other end the same distance and in the same direction.

Bluechips
11-03-2012, 09:12 PM
I built a bridge crane 15 years ago with a 24' span. I used v-grooved steel wheels on angle iron tracks. I won't comment on the strength of your materials, as I'm not an engineer. I work with a mechanical engineer and had him look over my stress and deflection calculations.

I used structural channel iron for the for the endtrucks with the webs back to back and the wheels between them. Steel spacers keep them at the correct spacing for the wheels. My wheels have a 1500 lb capacity and are equiped with roller bearings. I have not been able to find 6" wheels with that load rating again. Most have 1000 lb rating now. I believe the trucks are 40" long and cocking has not been a problem. I would be concerned about the plastic wheels developing a "flat spot" over time from the weight of the crane itself. Also, there will be considerable force trying to wedge the groove in the wheels apart.

My bridge beam sits on top of the trucks, as has been recommended.

As to aligning the rails. I mounted the rails after the main frame was erected. I laid one rail on top of the supporting beam and used a laser pointer in a level that I had to shoot a straight line down the rail. I made a simple gage with a v-groove that went over the rail and had a target line offset about an inch to one side. As I moved down the rail, all I had to do was keep the laser spot on my target line while tacking the rail to the supporting beam. The bridge beam with trucks was set in place with the other rail loose. I slowly walked the bidge beam down the track tacking the remaining rail as I went. The laser straightened rail guided the bridge and the other rail lined itself up.


Mike

darryl
11-03-2012, 09:21 PM
made a little drawing of my truck re-design.

http://img.photobucket.com/albums/v136/heinrich/gantrytruck.jpg

The holes are where the axles go- I didn't attempt to draw the wheels themselves, but it should be obvious where they go, between the plates. The added piece under the inside plates goes straight across under the beam. This acts as the inside flange, and the bottom of the outside plate is the outside flange. This lets the wheels be simply pieces of round bar, bored for bearing fits in each side. If you really need or want to keep the trucks centered on the parallel beams, you could use pieces of uhmw sheet attached to the inside of the plates- these would ride against the edges of the I beams to keep the wheels more or less centered over it.

I'm also concerned that plastic wheels might split on you, given the tension they would be under from riding the angle iron. Using my idea, you could still use the angle iron, but make the wheels from steel instead.

macona
11-04-2012, 01:14 AM
I would NOT use plastic for the wheels. Do not use "silver steel" for the axles.

You also want something to keep the trolleys on the rail, some sort of hook that goes over the flange.

In general that seems awful light for 750kg.

taydin
11-04-2012, 05:57 AM
Usually, the deflection of the various beams is the controlling factor, not their strength. For instance, AFAICR, in BS 466, the maximum deflection of the main beam is limited to L/900, L being the down shop rail centres. I'm sure ASME has something similar.

Not sure I understood the L figure. Is this the total length of the cross beam (In my case, 6m)?


Also the wheel centres on the end carriages look too short to effectively guard against 'crabbing'. They should be about 1/6th of the main beam span - again the standard will usually dictate this.

I guess you are talking about the distance between the two holes that support the wheel shaft being too short, hmm... What is the danger of this distance being too short?


It is also usual to consider a load of about 10%, acting sideways to the main beam, at the same time as the vertical load, to allow for off-centre and/or swinging loads. For an underslung hoist unit, this introduces torsion into the main beam - and 'I' beams are notoriously unstable under torsional loads!

This is something that I haven't really thought about. Thanks for pointing this out. When the load is large, this will definitely generate lots of sideways forces.


Finally, if, as I am, you are living in an earthquake prone region, you also have to have a margin for this phenomena!!

Major earthquake region here as well (last one being in 1999)

taydin
11-04-2012, 06:02 AM
Thanks a lot for all the great, useful responses. I am so glad that I posted my project here first. I will incorporate all the suggestions into the design and post the updated design.

Black Forest
11-04-2012, 07:31 AM
Darryl I am really pissed off at you! If you had posted that six pulley cable balancing whatchamacallit when I was building my sheep shearing machine it would have saved me a lot of headaches.

Forrest Addy
11-04-2012, 09:02 AM
That's not a gantry crane, thats a bridge crane - or am I being overly picky?

I'm nervous about your selection for bridge and rail members. There's a point over a certain slenderness ratio where failure mode for an I beam without lateral support is buckling before the design load is acheived. Also most bridge cranes are designed with a deflection limit a fraction of the beam's ultimate bending load.

Is this crane intended for use in the open unsupported by adjacent structure? If so you may wish to triangulate the corners.

Look again at the trolley wheels. Cast iron V wheels over inverted angle works pretty slick for car bottom ovens but their rolling friction is high. I suggest double flanged wheels on track or flat bar.

How do you propose to keep the bridge square with the rails? Maybe a drawing board straight edge, wire and pulley arrangement? Otherwise the bridge trolleys have to have sufficient spacing to resist slewing - say 1/5 the bridge span for example.

5 to1 safety factor is usual for crane structure. If your beam material is rated fot 35,000 PSI then figure max stress at 7000 PSI. Sorry about the Imperial units. I''d have to dig for the Metric equivalents but it's late here. I'm sure you understand.

140 mm beam for a 1.5M span 1000 Kilo load? I would think 200 mm would be more in line with commercial practice.

I'm not tryng to pick you to pieces here. Cranes mean suspended weights overhead and when they fail it's usually disastrous, damaging property and equipment if not lives. In the movies, structure fails with lots of visible bending, creaking, and ominous music. In real life it folds up without warning and collapses with a hellova crash.

Fireman11
11-04-2012, 10:44 AM
I don't know what I'm talking about (not a mech eng etc.) But I would think a 4x safety is way too low for a crane, especially a "garage" crane. I would want 20 or 40 x. You know if its designed for 750 and you have 1000 you have to move in the future what will you do? Also all the welds, bolted joints I would expect myself as an armature to be suspect and more vulnerable to aging and fatigue etc.

On the gantry beam, I would want the beam to extend over the side beams, with a piece of steel going 90 degrees down outside of the side beams. I think you would want the "wheel base" of the trucks to be much longer, and I would want a grossly over engineered "end stop" on the ends of the side beams. I wouldn't use plastic for the wheels, I would want some commercial wheels with rated loads a few times the the rated load of the crane each.

I have built a few sliding doors using steel v wheels (on glass furnaces) and one has problems with them coming off the tracks, I would be careful with this on a crane.

J Tiers
11-04-2012, 11:17 AM
One thing about the type of wheel setup that rolls on the bottom flange is that it basically cannot come off the rails.

And the best way to design is for the parts to be self-supporting even if not welded or bolted.... so that the moving beam actually sits on top of the wheel "trucks".... although I do understand about low height and clearance issues. Designed that way, there would be minimum dependence on welds, etc, for tensile strength. All it would really take is moving the side rails lower.

Definitely agree about length of wheelbase, such a short distance will tend to jam, or even come off the track.

And the drawn beam sizes are almost certainly too small, they are a large number of "flange widths" long..... Usually you want to be supporting the beam against side movement every 20 to 30 "flange widths" along it.

justanengineer
11-04-2012, 12:35 PM
No offense, but the basic design of your crane scares the absolute heck out of me. The way its drawn, the first time a chain or lifting sling breaks or the load starts bouncing the bridge, trolley, and hoist are going to land on top of your head. In reality, a safely designed crane does NOT rely on gravity alone to keep the bridge on the main rails. Also as already stated the safety factor does NOT apply to the choice of beam/rail used, but rather just to the fastener hardware. Its based upon a standard deflection vs unsupported length formula of the total design. Not sure what the laws are in your neck of the woods, but in many (most?) states here, any lifting device over a certain capacity (IIRC, 2 tons) or a certain size must be certified and inspected, regardless of private or commercial usage, which is making our antique cranes disappear along with their collectors in many areas.

My personal suggestion - buy a commercially built crane or forget it.

taydin
11-05-2012, 06:12 AM
I would NOT use plastic for the wheels. Do not use "silver steel" for the axles.

You also want something to keep the trolleys on the rail, some sort of hook that goes over the flange.

In general that seems awful light for 750kg.

Thanks for the comments. The plastic wheels will definitely go and be replaced with an end truck having 4 wheels. Will also make the end truck longer, maybe 1000mm. I am hoping that this will eliminate the cocking that darrly mentioned. If not, I will start working on the steel cable/pulley arrangement.

Do you think silver steel would make a good shaft for the end truck wheels, or is it still not recommended?

I will also add the hook to the bottom of the end trunk to prevent the end truck from getting derailed.

taydin
11-05-2012, 06:32 AM
No offense, but the basic design of your crane scares the absolute heck out of me. The way its drawn, the first time a chain or lifting sling breaks or the load starts bouncing the bridge, trolley, and hoist are going to land on top of your head. In reality, a safely designed crane does NOT rely on gravity alone to keep the bridge on the main rails. Also as already stated the safety factor does NOT apply to the choice of beam/rail used, but rather just to the fastener hardware. Its based upon a standard deflection vs unsupported length formula of the total design. Not sure what the laws are in your neck of the woods, but in many (most?) states here, any lifting device over a certain capacity (IIRC, 2 tons) or a certain size must be certified and inspected, regardless of private or commercial usage, which is making our antique cranes disappear along with their collectors in many areas.

No offense taken :) I was wondering how the cross beam could get derailed and your explanation makes it quite clear. It is amazing how much detail there is when it comes to designing this type of equipment. My country is following the European norms and it is possible that there is a certification and inspection requirement, never looked into it, though.

I did a few more calculations using Engineering Toolbox, which came with Alibre Design. First I did uniform beam analysis by using the crane for which a link was given earlier. This crane had a 12" high cross beam. I looked up the local equivalent, which is NPI300. Also assumed that the material is low carbon steel (1020). When loaded with 1000Kg at the center, that beam only deflects 0.5mm. My beam NPI140 deflects about 10mm. If I use NPI160, the deflection is about 5mm. I need to make sense out of these numbers first. For example, given the deflections, has a NPI160 double the carrying capacyt of NPI140? If so, NPI300's carrying capacity is 20 times as much as NPI140. If the guy that build the 2 ton crane has his numbers correct and his beam is rated for 2 tons, then my NPI140 would be rated for only 100 Kg :rolleyes:


My personal suggestion - buy a commercially built crane or forget it.

In order to fit into my shop, it would have to be a custom built unit, which I certainly won't be able to afford.

BigJohnT
11-05-2012, 07:29 AM
The bridge cranes used in the local industrial park have two important design details I see lacking in your original design, multiple vertical supports (short span between posts and the trucks ride on top) and they use the building structure to stabilize the post and beam part.

Just something else to toss in the pot.

John

J Tiers
11-05-2012, 09:21 AM
One thing to remember about beam deflections.. When you load the device, deflections will cause it to "run downhill" to the point where deflection is maximum.

If you have carefully leveled the thing to begin with, that will be the center, and if you have not leveled it, it will be somewhere else. Might be worthwhile to put in some sort of cable arrangement for moving the "trolley" and/or the moving beam, so that you can be sure of being able to actually move a load over the full area you intend to cover. It may not look like much deflection until you try to move the load.

generally, deflections are held to certain maximum amounts, so if you stay within that the job gets easier

macona
11-05-2012, 10:31 AM
Thanks for the comments. The plastic wheels will definitely go and be replaced with an end truck having 4 wheels. Will also make the end truck longer, maybe 1000mm. I am hoping that this will eliminate the cocking that darrly mentioned. If not, I will start working on the steel cable/pulley arrangement.

Do you think silver steel would make a good shaft for the end truck wheels, or is it still not recommended?

I will also add the hook to the bottom of the end trunk to prevent the end truck from getting derailed.

Silver steel, known by a lit of us in the US is tool steel. Thats is what it is designed for. A lot of people use it for everything because it is ground to diameter. The stuff is really not weldable. You will get hard spots. In this situation you need something weldable. I am betting most places use generic hot roll steel for the axles.

Use silver steel for what it is designed for, tools that need to be hardened. If you need something with a nice finish to start with buy TG (Turned-ground) or TGP (Turned, ground, polished)

macona
11-05-2012, 10:36 AM
In order to fit into my shop, it would have to be a custom built unit, which I certainly won't be able to afford.

I built my own gantry as have others. I would look at sites that sell gantry cranes an extrapolate from their designs, like here:

http://www.wallacecranes.com/thrftste_adjust.htm

At a 20' span and 1 ton (Pretty close to your 6m) they are using an 8" I beam, that is about 200mm. Quite a bit heavier than what you are looking for.

Forrest Addy
11-05-2012, 10:39 AM
Here's the parallel rule rigging some of us mentioned:

http://www.mayline.com/sft277/649.pdf

Look at the second page to see how the cable is arranged on the 4 pulleys to obtain parallel motion.

A similar arrangement scaled up to suit application for a bridge crane will prevent the beam and trolleys from racking on the tracks. The cable and pulleys if well arranged will add very little drag to the system. I'm thinking 6 mm 6 x 37 wire rope and 4" dia shrouded pulleys. Maybe modify V belt pulleys by re-machining the groove to accept the wire and installing a bearing in the bore.

outlawspeeder
11-05-2012, 01:27 PM
Thought about a crane myself. The basic plan was two side beams and two more with cross braces. That would stop the thing from twisting killing me. After reading all this, I’ll stick with my single I beam and roller system. That more than enough to lift the BPs of the trailer and set them down on pipes. I never thought about the deflection.

Thanks

It is not knowing what you don’t know that will get you killed!

Barrington
11-05-2012, 01:38 PM
The pulley system could be simplified even further - a parallel drafting machine only really needs four pulleys so that they can lie in a plane to prevent twisting of the ruler.

For this application I think just two (admittedly double groove!) pulleys would do the job :-

http://i564.photobucket.com/albums/ss82/MrBarrington/ParallelMotion.jpg

Cheers

.

Jaakko Fagerlund
11-05-2012, 01:56 PM
Yeah, don't use silver steel (a.k.a. drill rod), it is not meant for that use. If you want something good for it, get cold drawn structural steel, like S355. It has a usual h9 tolerance, meaning it will fit in to a H7 hole perfectly (sliding fit) and is uniform in shape and can be welded.

Paul Alciatore
11-05-2012, 07:46 PM
Here are my thoughts on a better design. The top part of the drawing shows a pulley and cable arrangement that only requires four pulleys and less cable than Darryl's. The down side is you may not want the cables crossing in an X in the middle of the shop. Perhaps Barrington's scheme is better?

The bottom is a crude cross section of a design that places all parts that support the load in compression loading. Almost any solid material is strongest in compression so this is perhaps the strongest, safest design. It also incorporates end plates that provide a fail safe if the wheels should ever try to jump off the track. It would ride close to but not rubbing the lower I beam. A vee wheel on a vee track is not the safest design and I would not want that cross beam plus any load it is carrying dropping on me, another person in the shop, or my machines.

http://img.photobucket.com/albums/v55/EPAIII/CraneIdeas.jpg

I drew the wheel trunnions as flat plate, but you could use I beam or channel equally well. Please excuse my misspelling on the drawing.

I used your vee wheel and track design, but if I were doing it I would consider a different arrangement. A single, flat wheel running in a channel welded to the top of the I beam may work. Or perhaps two train style wheels with flanges, one on each edge of the I beam. Or a flat wheel and two sideways wheels to keep the flat wheel on the I beam. These sideways wheels could run against the inside web of the I beam as an added safety factor. That would make it almost impossible for it to jump track. Two pairs of sideways wheels could help the tracking problem and perhaps eliminate the need for cables and pulleys. The pairs should be well spaced, at least 1/10 of the length of the upper, cross beam.

SVS
11-05-2012, 08:53 PM
Barrington's sketch shows the design I attempted to describe early in this thread. It's a proven way to go about things and could hardly be simpler.

wierdscience
11-05-2012, 09:18 PM
What your doing will work,it will work better if you can add a tension truss under the trackway beams similar to this bridge-

http://www.lkgoodwin.com/more_info/shop_crane/shop_crane.shtml

The parallel cable idea is a good one,but simpler and more positive still would be a roller chain drive.Have a look at this video where roller chain is used as a rack gear and a single sprocket used for the pinion.The two drives are connectd by a transverse shaft.If a handwheel loop chain sprocket were added to the shaft the bridge could be moved up and down the rails by force applied at the top nearest the load carrying trolleys.

This makes for a safer design and would eliminate a great deal of frame racking that would result from pushing the load rather than the trolley.

http://youtu.be/vETkf1sqo3M?t=2m35s

You could even motorize it later.

becksmachine
11-05-2012, 10:24 PM
Wouldn't it be far simpler to just gear one wheel on each end truck together with a lineshaft.

As has been done for the last 100-200 years?? ;)

Which would also allow for much finer positioning control using a simple hand chain to drive the lineshaft.

Dave

J Tiers
11-05-2012, 10:32 PM
Wouldn't it be far simpler to just gear one wheel on each end truck together with a lineshaft.

As has been done for the last 100-200 years?? ;)

Which would also allow for much finer positioning control using a simple hand chain to drive the lineshaft.

Dave

My thought also.... While it may not be as positive as the cable system, it seems a LOT easier.... the amount of added material is laughable considering the beams etc that will go into the structure to begin with.

Driving the thing with an endless hand chain is quite do-able, likely makes it move slower (safer on an inertia basis) , and can be geared down to work with quite heavy loads

darryl
11-05-2012, 10:55 PM
Barrington has the cable system nailed!

Using any of the cable systems keeps the travelling beam aligned, so there's no need to make the trucks long. I would keep them fairly short actually, so they don't add flex of their own. Just visualizing this, I'd say put your axles about 12 to 14 inches apart. That's a wide enough footprint to keep the beam upright, but not so wide that it would tend to fold up under a heavy load.

Using the cable, regardless of the configuration, I'd add some brackets with holes to pass the cable through. The brackets would be placed close to each pulley, and would guide the cable into the pulley groove. That way, even if the cable went slack (which it shouldn't anyway) it would stay in alignment with the grooves.

I am as concerned as anyone regarding keeping the cross beam from tippling. I can see a design in my head for some bracing which would help a lot, but it will also have a yield point. If that point is exceeded, the beam itself would rapidly collapse with little warning, so it may be unsafe.

Barringtons cable layout is what I had planned for my travelling table saw extension table. Pauls layout is what I've used on my table saw fence at home and one at work. The layout I first showed is like Pauls, but it keeps the crossover of the cables at one end and closer together. Bear in mind that you would need to brace against the towers pulling inwards for Pauls and my layout- for mine a brace across the towers at one end would be enough, for Pauls both ends would need to be braces, and Barringtons layout eliminates that need since the cross beam itself does that job.

wierdscience
11-05-2012, 11:45 PM
Wouldn't it be far simpler to just gear one wheel on each end truck together with a lineshaft.

As has been done for the last 100-200 years?? ;)

Which would also allow for much finer positioning control using a simple hand chain to drive the lineshaft.

Dave

So long as he has a safety clip or bottom flange roller to prevent the thing climbing off.V-grooved wheels will do that on occasion.

Barrington
11-06-2012, 07:11 AM
Barrington's sketch shows the design I attempted to describe early in this thread.
Apologies SVS - missed your post.

Cheers
.

Barrington
11-06-2012, 07:15 AM
To add a drive just replace one of the cables with chain, and drive from a sprocket (or sprockets) mounted anywhere convenient on the cross beam.

Add gearing/motor/handchain to taste.

Maybe simpler and cheaper to implement than a 6 metre long lineshaft ??

Cheers

.

SVS
11-06-2012, 10:05 AM
No apologies needed Barrington-A picture is worth a thousand words, and I'm glad you posted it.

Scott

2ManyHobbies
11-06-2012, 12:00 PM
Using any of the cable systems keeps the travelling beam aligned, so there's no need to make the trucks long. I would keep them fairly short actually, so they don't add flex of their own. Just visualizing this, I'd say put your axles about 12 to 14 inches apart. That's a wide enough footprint to keep the beam upright, but not so wide that it would tend to fold up under a heavy load. With the beam on top, the truck length is more to prevent beam tipping or twisting than it is to prevent cocking. Spacing wheels 150-180mm from the center of a +140mm beam on a 6m span will make things exciting when something binds.

taydin
11-07-2012, 05:59 PM
Ok, I have reworked the design according to the suggestions. Basically, the cross beam is now an IPE200 beam. Unlike the NPI140, this beam is higher (200mm) and it has flat inner surfaces. On the crane manufacturer link given by macona, an 8' beam is suggested for a 1 ton load. My goal was 750, so this 200mm beam will hopefully cover this.

I have also incorporated NPU80, U profiles with diagonal supports to counter side forces.

The crane posts are now IPE200 I beams as well. I didn't place any diagonal supports to the crane posts, because they are 200mm wide. But if there is instability of shaking, I can place the diagonal supports later if needed.

I am also using a cart type arrangement on the side rails with 4 wheels. The cart is 1000mm long, so hopefully cocking should not be an issue. If it will be an issue, I will look into implementing the steel cable and pulley arrangement suggested by darryl and others.

The number of crane posts is now 6 and the side rails are 3m each. I also placed diagonal support pieces to the feet of the crane posts.

http://www.taydin.org/web/vinc2/vinc.jpg

http://www.taydin.org/web/vinc2/vinc_ayak.jpg

http://www.taydin.org/web/vinc2/vinc_enine_destek.jpg

taydin
11-07-2012, 06:00 PM
The style of the carrying cart is almost identical to the 2 ton crane in the link that was posted earlier.

http://www.taydin.org/web/vinc2/vinc_araba.jpg

taydin
11-07-2012, 06:01 PM
Here is the cross section of the wheels. I have used angular contact ball bearings (spefically, 7206BEP), which have a static load capacity of about 1.5 tons. The bearing ID is 30mm and the OD is 62mm. The bearing width is 16mm. According to my "Tabellenbuch Metall" book (an excellent German reference book), these type of bearings are good at resisting axial forces, which will occur during cocking attempts of the cross beam.

What I am not sure about is the axle. I am contemplating to drill a 42mm hole into the 120x120x10mm angle, which makes up the side of the cart. Then I will press fit the axle into this hole and will weld up one side. The bearing will rest against the 42mm part and the tip of the axle will be threaded so that I can fasten the bearing to it. Is this adequate for this application, or should I use a single axle and mount both wheels onto that?

http://www.taydin.org/web/vinc2/tekerlek_kesit.jpg

taydin
11-07-2012, 06:16 PM
Here is the front view of the wheels. I will weld one side of the axle. The wheels are going to be steel now. I have also drilled three holes around the wheel so that it is possible to hammer out the bearing if needed.

http://www.taydin.org/web/vinc2/araba_on.jpg

Bluechips
11-07-2012, 06:25 PM
Since there is nothing between the wheels in your new design, why not carry the axle across both sides of the truck? That way you avoid the cantilevered wheels. May not be an issue, but couldn't hurt.

Mike

john11668
11-07-2012, 06:59 PM
"Since there is nothing between the wheels in your new design, why not carry the axle across both sides of the truck? That way you avoid the cantilevered wheels. May not be an issue, but couldn't hurt."


I agree bit why not take it a stage further and use a single wheel with two flanges, one at each corner !
Run them on a single rail welded upon the gantry.

Nice bracing / gussets to stop flex on cross traverse
How about some for long travel.

Line shafts are old hat now but how are you going to make long and cross traverse happen?
If it is manually driven the line shaft for LT is simplest.
Will you need to traverse and travel with the load ?
If you have electric hoist then electric traverse is not difficult.
This is the sort of project though when you dont know where to stop!

taydin
11-07-2012, 07:04 PM
This will definitely be manually operated on both traverse and longitude. I looked into crane motors and there are reasonably priced ones available. For example, there are this type of motors available rated 600Kg when used straight, 1200Kg when swung around a pulley (of course this will halve the travel speed). They costs about $220

http://www.hirdavatspot.com/modules/catalog/products/pr_01_7633_max.jpg

(Note that the picture is probably not the 600Kg model)

I have seen very nice motors with chain that also allow traverse travel. Also, these are designed for low ceiling applications, just like what I want. It will also fit very nicely into my cross I beam:

http://www.netlift.com.tr/folders/14026/productimages/5052/picture_first_k_b.jpg

But these came out to be very expensive, so not an option...

Black Forest
11-08-2012, 12:51 AM
The style of the carrying cart is almost identical to the 2 ton crane in the link that was posted earlier.

http://www.taydin.org/web/vinc2/vinc_araba.jpg


The one thing I see missing is a feature to keep the cart secured to the side rails. A feature to prohibit the cart from jumping the track.

macona
11-08-2012, 01:07 AM
I would not use angular contact bearings unless you use a pair. They are not meant to be used as individual bearings, they will come apart.

I would look at the 5200 series bearings. Double angular contact bearing in one housing. Pretty cheap too.

http://www.astbearings.com/double-row-angular-contact.html

darryl
11-08-2012, 01:33 AM
I like it better than your first one. I don't like the stud arrangement to mount the wheels like that- that's asking for the stud to resist a cocking motion, and that puts stress on the welds again. The axle should go straight through. I'm also not a fan of having a flange on the wheels- unless it's much wider than the wheel, that gives a lip which could ride up onto the track and derail it. If it cocked sideways, that's what I'd expect to happen. It's a potential accident that you do not want to build in and have to live with. If the angle iron was wider it would hang down below the rail and act as flanges. Since these would not be rotating, they would have no tendency to ride up the sides of the track.

With wider sides on the angle iron, the flange could drop down well below the edge of the track. I'd want about an inch or so- then you could mount some bolts through the bottom edge and they would extend inwards under the top of the I beam. That would give a positive 'catch' so the trucks could not lift off the track.

As far as 'adding the cable system later if needed'- do it now. It will be so much nicer (and safer) to roll the gantry along the rails, and it won't matter from where you pull it. Barringtons layout is the easiest, safest, and cheapest, and it doesn't have to interfere with the winch. 1/8 inch cable is all you need, and there doesn't need to be more than 50 lbs of tension on it.

One other thing- the way you have it drawn now raises the cross beam higher above the tracks than it needs to be. If you have a height limitation, you'd be wanting the cross beam to sit just above the tracks, say 1/4 inch clearance or so. My drawing allows this, and also allows the tracks to be placed closer to the walls of the room.

Going back the spacing of the cross beam from the tracks- I said 1/4 inch, but you could also make that about 3/4 inch. That would give you room for the double groove pulleys on the bottom of the cross beam and would keep the cables close to the tracks. This would give it the least tendency to tipple the cross beam if the cable had to work hard to keep one end or the other in line. This could happen if the weight you're lifting is near to one track. The cables would be crossing over each other within about 1/2 inch from the bottom of the cross beam, and it's likely that you would have this space anyway between the top of the winch motor bracket and the beam. By the way, where the cables cross will always be at the center of the beam. If you'd be worried about the cables chafing against each other, you could mount a short stub of uhmw at this point. It would have two holes in it for the cables to pass through, and the holes would just miss each other. Not only will this prevent the cables from chafing, it will support them at the center of the beam.

taydin
11-08-2012, 04:56 AM
darryl, my concern about the cabling and pulleys is that it will add resistance. The entire assembly will be pushed by hand in X and Y, so I would want this to go as easy as possible.

Regarding the through axle, in that case, how would I fix the wheels in the inner side? With the current stub axles, I was going to cut a thread in the inner side and use bearing nuts to fix the bearing into place. But if it is a through axle, I would probably need an O ring type arrangement. Would this be strong enough? I guess with the cabling system, all of this isn't a concern anymore ...

taydin
11-08-2012, 04:57 AM
The one thing I see missing is a feature to keep the cart secured to the side rails. A feature to prohibit the cart from jumping the track.

Thank you for reminding this. It was mentioned previously, but I forgot about it. I have placed another 100mm piece of angle to the center of the cart so that it extends towards the inside of the side rails. The angle is about 10mm away from the rail.

Black Forest
11-08-2012, 05:05 AM
darryl, my concern about the cabling and pulleys is that it will add resistance. The entire assembly will be pushed by hand in X and Y, so I would want this to go as easy as possible.

Regarding the through axle, in that case, how would I fix the wheels in the inner side? With the current stub axles, I was going to cut a thread in the inner side and use bearing nuts to fix the bearing into place. But if it is a through axle, I would probably need an O ring type arrangement. Would this be strong enough? I guess with the cabling system, all of this isn't a concern anymore ...

You would just use a bushing that slides over the axle. The bushing/sleeve would hold the two wheels apart.

darryl
11-09-2012, 01:43 AM
Taydin, you will find that any skewing of the gantry is going to cause you a lot more friction effects than the cable system will. One of my cable systems is tensioned to about 60-70 lbs estimated, and it takes only one finger pressure to move it. If you use 1/8 diameter cable and you wrap it around pulleys less than 2 inches diameter, it will take more force. My earliest cable control system uses 1/8 cable and 1-1/4 inch pulleys, and I can feel that I should have used larger ones. It basically takes two fingers to move the fence on this one. Your wheel bearings plus the incongruities of the wheels running on the tracks is going to take more force to move than that. And if the gantry skews- well, that's going to be frustrating to say the least. You want to carefully and safely move your load, not cater to keeping the gantry aligned so it can roll. I urge you to eliminate this problem from the start by adding the cable system in the build.

I thought more about this last night, and I realized that you won't be able to run the cables close along the tracks, as the wheels will interfere with it. But you can run the cables just outside the outer plate. That will mean the outer plates will need to be slotted so the pulley can protrude through them by a small amount. This would also keep the pulleys a bit further out and less apt to interfere with the full range of motion of the winch across the beam.

Note that this last suggestion is assuming that you place the pulleys underneath the beam. I still recommend to do this as it puts less tilting action on the beam, but you can put it on top and it will work. One thing that will happen is when the beam bends under weight, the upper mounted cabling will slacken slightly, and you might risk having a cable come off a pulley. But you can always add some guides, as I suggested in an earlier post. Provided your trolley with the winch hanging from it will allow you to string cable underneath the beam, I'd do it that way.

Last thing- look at Barringtons drawing again. Imagine that one cable was shorter than the other- the gantry will be skewed. It will be important to be able to adjust the length of both cables so the gantry can be squared up to the end beams.

NzOldun
11-10-2012, 04:47 AM
Not sure I understood the L figure. Is this the total length of the cross beam (In my case, 6m)?

I guess you are talking about the distance between the two holes that support the wheel shaft being too short, hmm... What is the danger of this distance being too short?

This is something that I haven't really thought about. Thanks for pointing this out. When the load is large, this will definitely generate lots of sideways forces.

Major earthquake region here as well (last one being in 1999)


Firstly, yes, 6000/900 = 6.7 mm. Assume central single point load of 750 Kg plus weght of hoisting unit. Will it be electric or hand chain block?

The 6:1 ratio is simply good practice arrived at from, literally, thousands of EOT cranes, It's not a fixed figure and there is no doubt you could reduce the end carriage wheel centres,
but my advice would not to go below 800mm.

I'm from Christchurch!!! About a third of the CBD has had to be demolished.

The "equivalent static" EQ horizontal load is now a minimum of ~60% of the all-up load, applied at the same time, although the allowable stress may be increase 20% for short time loads (EQ).

I have designed commercial EOT cranes, but not for several decades.

NzOldun