Need Collar Suggestion

Clear as mud...

Sorry for the mud. Maybe this will help: For visualization think of the shape of a valve in an automobile engine. I am using that hard steel rod in place of the stem, and I need a shaft collar or something like it to replace the bonnet.

I was considering using a set screw type shaft collar, but according to a seller of them, the set screw will not work as it cannot bind into the hard steel. So that is what I am looking for - what will bind into that steel solidly?

Better?

Sounds like a collar used as depth stop on a drill bit.

Grind a small flat on the rod where the set screw contacts and conforming to the shape of set screw end,; give it a pseudo socket or land.

You could add a set screw to a split collar too.

A taper lock.

Agree. A set screw cannot bite into hardened steel, so it will not be secure. Taper lock bushings will grip anything that is not too out of round.

"The collar will hit the block with substantial force at various times."

Depending on your definition of "substantial", without some mechanical interlock between the collar and the stem (other than friction), I would not bet on having much success.

There are numerous types of shaft collars using methods other than set screws. McMaster-Carr carries a fair variety.

http://www.mcmaster.com

www.uhing.com/en/id785.htm

Mcmaster carr catalogue page 1016 part #1058K12

I would recommend grinding a section of the rod down to 3/8"-7/16" dia. the width of a corresponding split collar, leaving approx. 3/16"-1/4" from the end at full (1/2") dia., and 7/16"-7/32" inside radius at the steps. As well, use some type of rubber washer as a bumper where C (the split collar) meets B (the block).

Maybe you should be asking yourself, "Do I need to harden the S7?" If the rod needs to be hardened, how hard does the rod need to be? Do I need to harden the entire length of the bar? Someone with induction hardening capabilities could selectively harden select areas of the bar for you.

I like the taper lock idea. nateofmt calls for quick removal. How quick, may determine whether the taper lock is acceptable or not.

After re-reading your question I'm questioning the use of a collar as you have represented it.

I suggest using a taperlok collar but in addition to an nylon washer/shim/spacer which ever may apply. The taperlok will positively lock in position and the nylon will take abuse from contacting the steel.

What do you think...

I have only seen taper locks used in rotation applications like the locking of gears or pulleys. I am not at all sure if it will loick hard enough on a rod like this to withstand slipping of in axial direction.

I would consider a split collar with set screws which seat in a small and slightly angled pocket. I would use 3 of these setscrews (not 4 as you cannot gaurantee true plane through all four so one will be there for nothing) and lock them in to contact with collar closed down. Then open the collar and give the set screw an eighth of a turn extra with blue locktite. Then you close the collar back down with blue locktite. Secure till doomsday and easily removed for very little cost.

Wow, thanks for all of the thoughts on this. I will explain more clearly what I am trying to accomplish. Attached is a picture of what I have drawn. I am not an engineer or draftsman - just had an idea, so this is probably pretty rough in some of your eyes.

The application is this: I am creating a driveshaft shield for offroad full size vehicles. Each end will get attached to a fixed point (I don't show those ends in the picture.)

Those fixed points are the cross member located at the transfer case and the differential. These segments are each 6" long with 1 1/2" gaps in which these sliders allow for expansion and contraction.

As the axle droops, the joints can expand or contract as necessary. When I say "substantial force" I am referring to the possibility that the axle droops suddenly, expanding most, but not all (don't want the shield to be the limiting factor of droop) of the segments out to their fullest reach, thus the collars would be up against the metal. I don't know how to figure out how much force that could be, but it seems that it could be "substantial" at some instant point.

The other thing I am dealing with is strength of the slider rods. How strong do they have to be if the vehicle dropped down 2' on a sharp edge? I looked at some steel on the mcmaster.com site and came up with "S7 Tool Steel Tight-Tolerance Rod 1/2" Diameter for the rods and 4130 Alloy Steel Aircraft-Grade Round Tube .750" OD, .120" Wall Thickness that would support the rods. But that was just a wild stab.

And as was noted by one poster, quick disconnect and trail repairable is a priority.

I looked at some steel on the mcmaster.com site and came up with "S7 Tool Steel Tight-Tolerance Rod 1/2" Diameter for the rods and 4130 Alloy Steel Aircraft-Grade Round Tube .750" OD, .120" Wall Thickness that would support the rods. But that was just a wild stab.

Suggest use, AISI SAE 0-1, A-2 or W-1 tool steels for there machinability, toughness and abrasion resistance if you must but I think is over kill. I've some experience at off-road racing equipment etc., strongly suggest use a 7500 series aluminum for the shielding. Think about the weight factor for the rods also a 2450 aluminum has the tensile of steel effectively, aluminum on aluminum is awful so bush well and you need consider using urethane bushings or graphite impregnated nylon as abrasion would be "RAD" upon the materials.

Also for field replacement suggest consider a tried and true retention method; a cotter key backing up a washer backing up a urethane washer.

I will look into those - but won't aluminum gouge easily being scraped over a rock? At some point this shield could be what the 3000 - 6000 lb vehicle is being supported on, and the driver could be romping it, bouncing and dragging this shield on the rock just as hard as he can.

I can't find any 7500 or 2450 aluminum. I must be looking for it the wrong way - can you provide me a link or some other way to search what I am looking for?

Oops! Look for 2024 and 7075 and they are tough but great machinability, high strength to weight ratio.

When this is fixed under your drive shaft and you want it off, how do you get access to the collars?

Many of the solutions we have talked about require you to have full access over the whole radius of the device to get it off.

There are two methods - number one is that the bracket that attaches it to either the diff or to the crossmember only needs one or two bolts removed to drop it to the ground.

Otherwise, depending on how much lift the vehicle has, a person should be able to just reach over the edge of the shield and remove the pin/collar/whatever and put the replacement one in.

Either way, it should be easier than replacing a u joint, pinion, or driveshaft.

If you knew the extension of the shaft to it's maximum point, you would never need to secure for the "considerable force" as your collar would never see the end caps.

If at all possible, always design to limit force and reduce the requirements for excessive detail and difficulty. Keep it simple. If you need a slider that can move 1" but it can hit the end cap at force, give it 0.1" over so it does not ever see the end.

The other thought I had was dirt. How do you think your device will live up against dust, sand, mud, oil leak, and rocks flying about? Can anything get stuck there and do more damage than you are trying to prevent? I have had a stone stuck in a brake disc protector plate and had to renew the disc.

There will normally be 6-8 of these segments for a rear driveline application. So with the vehicle running at flat level, the bottom ones may be close together or even closed, while the top ones remain open. Simply gravity pulling down would do this.

When the vehicle is pointed uphill, the bottom ones would be closed. When the vehicle points downhill, the opposite would be true. Forward and reverse movement on an obstacle then also can change this. But at some point, as far as I can tell, there will be a point reached at which something is going to limit the travel on each individual rod. The reason I picked 1 1/2" between sections is so pebbles, sand, dirt, etc could fall out, plus over the 6-8 sections it would be able to expand the same amount as the driveline moves over its splines. That may be able to be taken down to 1", but have to research more custom drivelines to see what kind of travel they can have.

The only times that normally it would be closed is when the axle goes into compression, bringing the drivetrain parallel to the ground.

Maybe a design flaw????

As far as dirt, etc. The gaps between the segments should allow dirt, pebbles, etc to get out. Also, holes could be bored out of each segment if necessary. At the differential end there is a large space for anything that has ran down there to get out, but it cannot get to the pinion yoke.

The design of this calls that for every compound angle (vertically and horizontally((minimal horizontal movement in axles, though))) that the driveshaft is at, this protection parallels it at a fixed distance away from the driveshaft. In other words, there shouldn't be a case where something larger than the distance between the driveshaft and protection can get in - minimize this as much as possible and it is very safe.

Also note that this is the same as adding skid plates - they allow an off roader to push the extent of their vehicle, until they break something else.

Are there any existing designs you know off that have already solved this problem?

That would always be my first attempt at solving something that looks like it should have already been done by others.

Sounds a nice little project with scope for trial and error as well. Hope you get on with it and report back to let us know how you think you progress.

nateofmt,

Really think 1/2" bars will support the weight of a truck?? I'd think that something akin to the ladder bars we used on our old hot rods would engage with more effect. I'm sure you've considered this already and your direction is commendable.

If used as protection devices rather than traction...

Taper lock anythings look very expensive for my application.

Taperlock is expensive as it is very accurate in rotational directions. It is therefor used for the fitting of precision gears and such. I don't think it would do the job anyway as you would have to be able to rotate the taperlock to get all the screws out of the pressure plate before you could remove it from the shaft.