PDA

View Full Version : DD socket



alsinaj
10-28-2017, 05:37 PM
I need to make a socket to drive a DD shaft 5/8" in diameter and 3/8" between flats. The only way I can think of to do this without making a broach is:
take a piece of round bar of somewhat greater diameter and length than the desired finished dimensions
bore a 5/8" hole through it
mill off top and bottom, leaving the desired 3/8" in the center, and also leaving the excess length intact at both ends
braze plates onto the milled flats
turn the assembly to finish outside diameter and part off the excess at both ends

Is there a better way?

kitno455
10-28-2017, 07:38 PM
Buy a 5/8 DD steering coupler, and weld it onto your assembly.

allan

alsinaj
10-28-2017, 07:46 PM
kitno455: Thought of that first, but found only 3/4" couplers. Do you have a source for 5/8" couplers? Thx. J

MikeL46
10-28-2017, 08:19 PM
Why can't you mill it out with a 3/8" endmill? The rounded ends won't match, but the flats that transfer torque will be fine.

Mike

Norman Bain
10-28-2017, 08:29 PM
Is the intended purpose of the socket coupling a "sliding fit over the shaft" or "fixed clamped"?

You had better tell us if the coupling is to be used in automotive steering; if so then the result will need to be well made.

If is just to drive a shaft on your yard tractor; then the approach you describe will work just fine. If is a sliding coupler then I expect that is should be hardened to improve longevity.

JRouche
10-28-2017, 08:53 PM
Here is a simple one. 1" round bar. Drill to 5/8". Cross drill two opposing holes (1/4" or less depending on needed strength). Insert 1/4"(or smaller) rods into holes to create a 3/8" gap inside of the 5/8" hole. Weld outside of pins to secure. JR

alsinaj
10-28-2017, 09:26 PM
Norman: The purpose is a sliding fit over the shaft. Not automotive. Not a lawn tractor, but close. Want to use the augur drive on my snowblower as a PTO to drive a big "manual" winch. The input shaft on the winch is DD shaped.

JRouche: That would work. I might take the OD up to 1 1/8". Only concern is that the contact between the input shaft and this "female DD" socket will be reduced to two points, one on each rod. That will probably result in the rods and/or the input shaft getting buggered up quicker than the approach using flat plates, where at least in theory there would be two line contacts.

alsinaj
10-28-2017, 10:04 PM
MikeL46: I think you may have the key to the answer, i.e., that the female part doesn't have to match the 5/8" radius on the input shaft. A rectangular opening 5/8" x 3/8" would work just fine. That can be made by making a U-shaped part with a 5/8" wide by 3/8" deep channel in it, and welding a plate on top to close the channel.

BCRider
10-29-2017, 12:13 AM
MikeL46: I think you may have the key to the answer, i.e., that the female part doesn't have to match the 5/8" radius on the input shaft. A rectangular opening 5/8" x 3/8" would work just fine. That can be made by making a U-shaped part with a 5/8" wide by 3/8" deep channel in it, and welding a plate on top to close the channel.

What about two pieces of channel welded down the middle of the "flats"? And if you use a radius corner cutter you could avoid the stress concentration that would otherwise occur at the square corners.

It wouldn't be all that perfect but if you have a two flute HSS endmill with chipped corners you could grind and match up by eye some 1/16" radii on the corners. I bet it would be close enough to provide that reduced stress concentration points in the corners.

Norman Bain
10-29-2017, 01:10 AM
... The purpose is a sliding fit over the shaft. Not automotive. Not a lawn tractor, but close. Want to use the augur drive on my snowblower as a PTO to drive a big "manual" winch. The input shaft on the winch is DD shaped...

More questions as to the layout:

* Is the winch to be attached to the snowblower.
* Is there to be a universal joint or two between the PTO and the winch.
* Is there expected to be need for some lateral movement in the driveshaft length.
* If there is to be lateral movement is that going to be managed in between the universals or at the DD connection.


I expect that the design will come out (evolve) as you work at it and the fitting at the DD shaft will become less of an issue.

To add to the options (hopefully without over complicating it all) ... it might an option to weld a different fitting to the male DD shaft. Not welding onto the shaft itself; but rather to the end of the shaft so that the weld on the coupling can be ground off to the remove that coupling later if needbe.

wtrueman
10-29-2017, 02:48 AM
Even easier. Get a piece of the 1/2 inch flat bar used for concrete forms. Clamp it around the needed shape, tack weld and grind as nessary. I have used this for a quick fix. Good luck.

ironmonger
10-29-2017, 09:35 AM
Drill a 1/2 hole is a suitable length of 1" round stock.
Make a tapered drift that has the desired cross section in the middle, for one time use it can be mild steel. I'd prolly make it .020" over size. (SWAG)
Heat the bored stock to a cherry red or a little hotter and drive the drift through the 1/2" hole.
Weld it to your shaft to drive the winch.


The profile, as far as the ends are concerned, looks like this

http://www.brentbaileyforge.com/thestore/chiselspunchesdrifts/reveal.jpg




You will have to make the cross section look like whatever shape you want.
If you make the drift, bring it over and I'll heat it and drive it through for you

alsinaj
10-29-2017, 10:33 AM
Norman: Good thought, but the input gear of the winch is driven by the DD shaft, so I don't want to change the end of the shaft in a way that would prevent me from removing the gear (which, in turn, would prevent me from disassembling the winch). It is a 2-speed winch, with speed selection being accomplished by sliding the input shaft longitudinally. On my snowblower, the "PTO" is an 8-inch v-belt pulley mounted on the augur assembly. The winch assembly, which will be a bolt-in replacement for the augur, therefore needs to include its own input pulley. Since the input pulley is stationary and the winch input shaft slides, there are two choices:
1) the input shaft and pulley don't move, and the rest of the winch slides sideways to change speeds, or 2) the winch and the input pulley don't move, and there is a sliding joint between the input shaft and the pulley. I've been working on solution 2) because I haven't yet thought of a way to mount the winch so it can slide accurately between two secure positions. Maybe I haven't thought about it hard enough.

Ironmonger: Thanks for reminding me that machining isn't the only way to shape metal. IMO, yours is the easiest solution so far, and at least as strong as the others.

Norman Bain
10-29-2017, 03:50 PM
What is it you are trying to achieve. That is, are you creating a recovery winch (like a 4WD winch) or are you trying to create a mechanism to "tow" tree branches and the like towards the winch from places you cannot get to.

Regardless I have it the winch should be fixed; and fixed solid enough to handle the towing stresses. Seems like you will wind up mounting the winch inside the metal shroud where the auger once sat. Is that area strong enough?

How about a picture of the actual snowblower; or a link to one very similar.

Arcane
10-29-2017, 04:08 PM
Why can't you mill it out with a 3/8" endmill? The rounded ends won't match, but the flats that transfer torque will be fine.

Mike

This would work as well as anything and is very easy to do on a mill. If you really have your heart set on matching radii on the ends of the slot, they do make 5/8" round files. Buy (or borrow :D) one and grind two flats accurately on opposing sides so it's 3/8" thick and simply file the ends to shape.

Paul Alciatore
10-29-2017, 04:34 PM
I like this method best as it will not have any welded or braised joints as possible points of failure. And the internal radii in the pocket will be 3/16". And you want a sliding fit and heat processes may cause problems if you want that to be a fairly close fit.

Another possibility that I do not believe was discussed above is the way one of my chuck keys was made. It has a square hole to fit a male, square head. It was milled from the side with a standard end mill, much like a short, wide, very deep keyway. This formed three flat sides of the square with two right angled corners between them. Then a plug was fashioned to fit in the side which the milling cutter cut away and that was braised in place to form the fourth side of the square hole. All four corners were completely square. In your case I would use a milling cutter with rounded corners (1/16" radius) and cut the slot. Then fashion a similar plug and braise it in place. This would be stronger than braising or welding two fillers in a cross slot.

Oh, and I am not any kind of expert at braising or welding, but in this case I would think braising would be better. A weld will only penetrate part of the distance of any joint and will therefore be somewhat weaker. Braising will allow the filler to penetrate the whole depth of the joint so, if properly done, it could (should?) be the stronger of the two.




Why can't you mill it out with a 3/8" endmill? The rounded ends won't match, but the flats that transfer torque will be fine.

Mike

alsinaj
10-29-2017, 05:04 PM
Arcane: Never thought of that. You do have to have a grinder, though.

Norman: Thanks for your interest. A photo of the snowblower can be found here:

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwid--Dy3JbXAhWDz4MKHXZmBQsQjRwIBw&url=http%3A%2F%2Fyoapandyoap.com%2Fevent%2Fhuge-auction-of-real-estate-tools-household-for-tony-zahringer-in-gresham%2Fcraftsman-snowblower%2F&psig=AOvVaw2Wf4Cr1_G7MwXPFVeTeGi8&ust=1509397039066813

The object of the excercise is to have a powerful, self-propelled winch for pulling logs and brush over rough terrain with steep hills. The snowblower (with augur and associated sheetmetal removed) has two purposes: 1) to get itself to where I want the winch, and 2) to turn the winch input shaft. The cable will spool out to the left or right of the snowblower; the opposite side of the winch will be attached to a cable or chain that must be secured to an immovable object like a tree or a sturdy metal stake driven deep into the ground. Some care will be required to position the snowblower so that the winch is oriented on a straight line between the anchor and the load, so that the only forces applied to the snowblower when the cable is drawn tight are in a downward direction. In principle, all the towing stresses are borne by the anchor chain/winch/winch cable assembly. The snowblower is just along for the ride, and to turn the input shaft. I've given some more thought to the idea of making a new input shaft that would carry the input pulley (no joints). This shaft would be mounted in a fixed position on a platform bolted to the snowblower. The rest of the winch would be able to slide 1/2" left and right to engage the high and low speeds. If pins are welded to the bottom of the winch that slide in slots in the supporting platform, and a large clamping bolt is provided to lock it in one or the other position, that should be sturdy enough, I think, since the platform only has to keep the winch from twisting out of position with regard to the rest of the snowblower. The platform, made of 7 ga steel or thereabouts, will bolt to the original augur mounting holes with eight 10mm screws. Does that sound reasonable?

Norman Bain
10-29-2017, 06:27 PM
Ok; so from the link I am presuming that the snowblower is a Craftsman 26" or 29"; let us know if the image below is a reasonable representation of the layout.

If so, then I have it that the motor output shaft is geared down some to connect to a driveshaft to what looks like a worm drive gearbox that then drives the auger.

I presume from your description that your design thus far involves removal of the worm drive gearbox.

There will need to be some means of starting and stopping the winch. Does the snowblower (with worm drive gearbox removed) have that stop/start clutch?

The winch must have some "free wheel" capability to unwind the wire. The rewind is of course done with the motor.

http://downloads.purposebuilt.com.au/NJB/Sundry/SnowBlower.jpg

Removal of the metal work auger shroud looks like it may give you pretty clean access to the body/chassis of the blower.

Mounting the winch direct to some frame that is in turn mounted to the blower seems reasonable to me. That said, the drive connection cannot be fixed solid; it should be some sort of flexible coupling even if it is only like the one in the image below.

http://downloads.purposebuilt.com.au/NJB/Sundry/Coupling.jpg

The couplings are about $10 ex eBay. NOTE: this is not a "cut aluminium" thing; it has an internal set of separating pins that allow greater missalignment than the simple cut aluminium type. I think that this coupling would clamp ok to the DD shaft as is without modification. Perhaps use two of them; one each at the blower and winch ends. Between them a sliding drive shaft for the gear changes.

Would I suggest movement of winch in order to change the gears. The answer is NO. Leave the winch fixed to the blower. There needs to be care (as you have suggested) to ensure that the strain load on the winch is managed by the anchor chain attached to the winch. The blower should be allowed to "float" to where ever the winch takes it.

Having the winch fixed firm to the blower means the gears need to be changed via a sliding mechanism in the driveshaft. That could be a simple as some round bar stock with a pipe over it. The pipe to have a slot in it and the bar stock a drill/tapped hole that takes a couple of bolts. The drive is via the bolts in the slots. The slide is the pipe slot along/over the bar stock.

The pipe portion could have a welded (or bolted) short portion of the round bar stock to allow it to connect to the connector.

[EDIT] Maybe some cheap universal joints would allow more flexibility in the alignment/placement of the winch. Just gotta get that driveshaft about 8" or so long.

alsinaj
10-29-2017, 08:51 PM
your design thus far involves removal of the worm drive gearbox.

Correct.

Does the snowblower (with worm drive gearbox removed) have that stop/start clutch?

Yes.

The winch must have some "free wheel" capability to unwind the wire.

Yes, it does.

Regarding a flexible joint somewhere in the input shaft, let me argue this point with you. If the following seems pedantic, it's because it's hard to make clear in writing what would be obvious from drawings, which I have but don't want to take the trouble to post (yet). A flexible coupling is generally used when the driving end of a shaft can become misaligned with the driven end. By having the drive shaft stationary with regard to the blower and sliding the winch to change speeds, the input shaft can be made in one piece, thus making a joint unnecessary.

Let me explain. In this snowblower, the auger drive is as follows: the engine crankshaft carries two v-belt pulleys. One activates the driving wheels through a loose/tight idler wheel mechanism. The other has a similar clutch mechanism activating a pulley mounted not to the snowblower itself, but to the augur subassembly. So far as power transmission is concerned, the only connection between the blower and the augur assembly is the v-belt. Thus, when you remove the augur assembly, you are left with a crankshaft pulley, a lever-operated idler wheel, and a belt hanging loose. When I replace the augur assembly with a fabricated winch assembly, that assembly has to have its own pulley mounted in the correct position with relation to the belt. This is easily done with pillow blocks or flange mounted bearings.

Now I have a winch input shaft with a pulley on one end mounted in a fixed position. I would machine the rest of shaft to incorporate the DD shape necessary to drive the input gear, a handle on the far end to accommodate the standard manual drive handle, etc. In order to preserve the ability to change speeds, the rest of the winch has to slide +/- 1/2" longitudinally along the shaft. Keys running in slots would assure proper alignment of the winch and the input shaft when sliding, the winch is already equipped with a detent mechanism that stops the sliding in 3 positions: high, neutral, and low, and a large threaded post with a big nut and a thick washer would clamp the winch body to the supporting platform when it is in one of the 3 legal positions. This approach allows me to make my new input shaft 7/8" in diameter instead of the original 5/8". Considering that a 9 horsepower engine is considerably stronger than any man's arm, that would seem to be a good idea.

I realize that having a stationary drive shaft and a sliding winch body, rather than the opposite, is counterintuitive. I started out designing a sliding shaft solution, but since the pulley must remain "unslidden," a sliding joint is unavoidable. Other than the work required to make said joint, it is also a likely point of failure when driven by an engine instead of an arm. This problem made me reconsider, and it now seems to me that a sliding winch design, if properly operated, may in fact be stronger and simpler to make.

Have I managed to change your mind?

Norman Bain
10-29-2017, 10:26 PM
... By having the drive shaft stationary with regard to the blower and sliding the winch to change speeds, the input shaft can be made in one piece, thus making a joint unnecessary. ...
....

Fixing any two rotating shafts in manner described is problematic. Not saying it will not work; just that there is a "shaking" at that connection (because it can never be 100% aligned) and the vibration needs to go someplace. It will work for a time and that is ok as well. Also, by your description the winch is not "totally fixed" (it is on a sliding base of some kind) so the vibration/missalign can go there.


... Have I managed to change your mind?

For me I am ok just to follow along and put in my 2 cents worth. Tis your project and I am comfortable with it being your call.

Will follow the evolution with interest.

tom_d
10-29-2017, 10:32 PM
Your original thought for making the DD profile by drilling a 5/8" hole in a shaft and milling off the sides looks like a good solution. Design the side plates to allow for a weld bead instead of brazing. Make the shaft from a high strength alloy like 8620 which welds easily and has good wear properties for the sliding joint.