DD socket

[Paul Alciatore]

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]

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=...09397039066813

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]

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.



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.



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]

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]

... 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]

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.