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View Full Version : Need to build a ratchet...ideas please?



torker
11-17-2007, 08:09 PM
Hey guys! Okay...I'm in a good one right now. Was approached by a mini golf course owner to build a golf ball asculator that would carry a ball up 12 feet and dump it into a replica train loci to continue it's journey to who knows where.
Anyway..I've got the thing near lockup but need a ratchet on the big handwheel that's going to drive the chain and ball scoopers. I need a ratchet so the wheel can't be turned backwards as it'll bugger up the ball loading mechanisim. Haven't got the wheel done yet but its a 5 spoke steel wheel 24" in diameter.
That being said, I need to make a ratchet that'll last for prolly a million turns. I'm concerned that the teeth and pawl will wear so I'm wondering what you all would make this out of?
That 24" wheel will transmit a lot of torque on everything when one of the little angels (snot nose brats) starts ramming on the ratchet for hours on end.
I'm thinking a 6 or 8" ratchet wheel. I'll post some pics of this creation when I get it a little further along.
Thanks!
Russ

lane
11-17-2007, 08:16 PM
make the ratchet from something so you can flame harden the teeth. 1045 ,4140 are something smiler. the pall make and case harden the tip. should work ok.Are use 01 heat treat and draw back to 38-40 Rc.

tony ennis
11-17-2007, 08:19 PM
If you put a ratchet on it, you better have a release in case someone gets hung up in it.

There won't be a lot of stress on the ratchet since normally people won't be spinning it backwards. If it is outdoors, I'd go with stainless.

Peter N
11-17-2007, 08:20 PM
I would have thought you could make the wheel from a medium carbon steel, 1045 (EN8 over here) or similar, and case harden it.

As the pawl will be taking more wear, then my choice for this would be EN19/4140. You can through harden this or perhaps better, have it nitrided to provide a very hard wearing surface.

The EN19/4140 has excellent shock resistant properties which could prove useful for this application.

Peter

wierdscience
11-17-2007, 08:21 PM
Two things come to mind,a tractor PTO over running clutch or a conveyor back stop clutch,both are sprag clutches.TSC should have the over run clutch and any conveyor company should have a backstop clutch.Both are built heavy and should last until everyone is too old to care.

John Stevenson
11-17-2007, 08:30 PM
Needle bearing roller clutch.

.

torker
11-17-2007, 08:44 PM
Holy Smoke! That didn't take long! Thanks for ideas!
The whole thing...chains, scoops etc. are all encased so nobody can (hopefully) get stuck in this contraption. It's built sorta "railroadish" to fit in with his replica steam engine.
As the place is usually unsupervised I've looked at most possibilities. I keep seeing (in my mind) a skinny redheaded kid with a roostertail and a bad attitiude....standing there all day clanging the handwheel back and forth all day while his parents are in the motel room sleeping :D
I'm going to check out those clutches as he could replace them without any custom work. Making him a spare set of parts would be better for the ol' wallet though.
Thanks again!
Russ

tattoomike68
11-17-2007, 09:13 PM
A boat winch has a nice ratchet that could be cannibalized to do a job like that.

tony ennis
11-17-2007, 10:28 PM
Or perhaps he's got a tired come-along that's ready for a new life.

jacampb2
11-17-2007, 10:58 PM
I have no idea what it is called, but how about the brake/hub assembly from a kids bike, you know, the kind where you jam backwards on the pedals and it locks up. They get abused by millions of youngsters and in my youth, I never had one fail. Should be inexpensive as well.

Later,
Jason

heavysteamer
11-17-2007, 11:21 PM
Like John S. said, needle bearing roller clutch.

Tinkerer
11-18-2007, 04:32 AM
I'd make a simple arrangement with an old gear and a spring loaded paw.
Kinda like this here ruff drawing

http://img.photobucket.com/albums/v665/A-Tinkerer/gear.jpg

The paw bottoms out in the U channel preventing backwards movement.

spkrman15
11-18-2007, 08:04 AM
Russ,
You can buy one way bearings from GBS and other type of stores. We had them at the ski hill (they aren't cheap). They would hold a 100hp motor no problem. As for reversing it, just put shear pin or bolt in the shaft. Remove the bolt and you disengage the shaft that has the bearing mounted on it.

My suggestion is to build the saft with the wheel as normal and just add a coupling going to the one way bearing. Remove the coupling and you can change the belt or rotate the shaft backwards by hand or with the motor.

Childrens bicycles have them in the rear. Pedal forward you advance, push backwards and the rear wheel locks.

Rob :)

Your Old Dog
11-18-2007, 08:15 AM
A boat winch has a nice ratchet that could be cannibalized to do a job like that.

This has the added advantage that you could dismantle 2 or 3 winches and bolt or rivet up all the rachet plates to beef it up. Should also be the cheapest. If it wears out in 5 or 10 years then make another. It has the advantage also of having a reversing setup for the redheaded kid with the rooster tail :D

GadgetBuilder
11-18-2007, 10:52 AM
Saabs in the 1960's used a free wheeling clutch so when you took your foot off the gas the engine went to idle and the car coasted - great for a 2 stroke since it didn't have much engine braking anyway. If you could locate one in a junk yard it could perhaps be adapted. This may be a version of the "needle bearing roller clutch" John mentioned earlier?

I borrowed this idea for a clutch to allow winding a clock as seen here:
http://www.gadgetbuilder.com/Clock/Clutch2.jpg

This a light duty version but it would be straight forward to make one totally from steel with hardened rollers. This clutch is silent, no clicking as normally heard when winding a clock. I used gravity to bring the rollers into contact so only one or two are active.

I believe the Saab version used springs to maintain all rollers in contact. The Saab free wheeling clutch was relatively small, about 6" in diameter and had a defeating mechanism so reverse would work normally - this would provide the lockup mechanism you need.

Another thought would be the free wheeling clutch from an overdrive transmission - I don't know the mechanism used but the function seems similar to what you need.

John

Herm Williams
11-18-2007, 11:59 AM
Another idea would be to take one from the tie down binder on a truck trailer, the ones for straps. about three inches in diameter very strrong and easy to release.
re

Ernie
11-18-2007, 02:00 PM
Another clutch system I've seen is used a lot in printers etc. that have a lot of gearing and is used to prevent them from going backwards. It's nothing more than two shafts, one at each end of a spring. The OD of the shaft is just bigger than the ID of the spring. Rotating one way tends to expand the spring freeing the wheel. Trying to rotate the other way tightens the spring and it locks up. No gears or ratchet or pawls. Actualy, no moving parts except for the sliding shaft in the spring.
Ernie

Mike Burdick
11-18-2007, 04:29 PM
Russ,

How about a couple of spring loaded dogs and something to catch them. Unhardened mild steel will probably last for the life of the equipment and the dogs can be made fairly thick. This way, it has very little machining and can be welded. For an example think "ground driven hay rake".

Peter Sanders
11-18-2007, 06:54 PM
Hi
Anyway..I've got the thing near lockup but need a ratchet on the big handwheel that's going to drive the chain and ball scoopers. I need a ratchet so the wheel can't be turned backwards as it'll bugger up the ball loading mechanisim. Haven't got the wheel done yet but its a 5 spoke steel wheel 24" in diameter.

Just a thought...

You didn't specify the distance travelled along the circumference of the 24" diameter handwheel.

As this is a large handwheel, perhaps there is enough circular distance to allow a small bearing to run on a "cam type" of follower attached to the wheel. This bearing would then raise the pawl (slightly) above the tooth, dropping it down again as the bearing rises and falls on the follower.

Such a method - with a quality bearing - should last several million turns :)

torker
11-19-2007, 12:12 AM
Guys...Thanks for all the great ideas! I'm going to have to check some of this stuff out. I like the idea of using an off the shelf part so it can be replaced easily down the road. The owner of the place is about as mechanical as a cornflake so I'd like to keep it simple for him.
Thanks again!
Russ

tony ennis
11-19-2007, 12:38 AM
as mechanical as a cornflake

woop! Woop! WHOOP! New signature alert!

camdigger
11-19-2007, 01:18 PM
Russ

The simplest and cheapest ratchet I've ever seen is a sprocket and long bolt arrangement seen on the rental dry wall lifters for doing ceilings. The sprocket is welded to the drum and driven by oversized steering wheel equipped with a spinner knob. The long bolt runs across the teeth of the sprocket on center. The hole on the sprocket side is elongated enough so the bolt will allow the sprocket teeth to pass while pivotting in the slightly over size hole in the end plate on the other side of the drum. Easier to make than to describe.

Cam

ProGunOne
11-19-2007, 03:49 PM
If you decide to go the roller clutch/sprag, needle bearing roller clutch route, you'll find the needle bearing roller clutch aka sprag/roller clutch here under their e-trans parts catalog. The GM TH350, 400, Chrysler 727 as well as many others have the roller clutches or sprags. For about twenty dollars, you could purchase one new. Or-if you or somebody you know has an old rear wheel drive core lying aroud to scavenge maybe?


http://transpartsonline.com/

torker
11-19-2007, 08:38 PM
Cam..another good simple idea!
Pro one..I was thinking of a Th350 sprag also. Only thing that bothers me about that would be the lack of lubricant. I believe I have three or four of those out in the shed.

reality checker
11-21-2007, 10:07 PM
Just about any starter drive would work. Pick something like you find in a delco from a chev and you can get on cheap and just about anywhere.

retusaf99
11-22-2007, 01:04 AM
I saw pics of a guy who made his own drywall lift. He used an old circular saw blade for the rachet. Lots of tooth/diameter possibilites there, or tack weld several together for something wider.

Doug

torker
11-22-2007, 08:25 AM
LOL! More great ideas! Thanks guys!