Now that I am home from Hershey with two more brake cross shafts, I intend to rebuild all three that I have over the winter. I have searched for and read every post (there’s lots of them) associated with these cross shafts and have a question that I can’t find an answer to on my own I’m planning to make new bushings using UHMW. It looks very straight forward once everything is taken apart. My question is: should I machine the bushing that the frame bracket bolt goes through to accept the steel spacer (I assume the spacer is there so that the bracket can’t be tightened hard against the frame) or can I just machine the UHMW to the length of the spacer and the diameter of the bolt?
Not sure what UHMW is but the bushing that I believe you are referring to is a rubber bushing .Check out Filling Station number 60-371. Checked the UHMW on line and it does not appear to be a flexible material and the bracket mounting bushing needs to flex.
You are correct that UHMW (ultra high molecular weight) polyethylene is not flexible. I was planning to make that bushing in a donut shape like the other, bigger bushings on the main shaft. It would be a different shape than the rubber bushings. Chevrolet engineers didn’t have this material to work with in the early thirties.
Which way do the bushings need to flex? My design will allow the bracket to move forward and backward, but not up and down, and the steel spacers prevent side to side. So I’m back to my original question …- should I use the spacers or not?
It is comforting to know that if what I’m planning doesn’t work, I can always buy the rubber bushings. I just really like making some of this stuff myself and I enjoy the lathe time.
I could not find FS part number 60-371 in the printed catalog, although I did find it in the Steele Rubber catalog (Steele’s number 60-0371-24)
I am at a loss to understand why Nylon or Delrin are not at the top of the list as bushing materials. Both are known excellent bushing plastics that machine well and are not too expensive. I have considered making those bushings in two pieces so the ends of the shafts didn't need to be removed. When I run out of other projects I will probably try it unless someone else makes them available.
I think it best to use the spacers. The rubber bushing allows it to react similar to a spherical bearing and I think a solid bushing will bind as when the brakes are applied the cross shaft could move so one side is say at an 89 deg. angle to the frame while the other is 91 degrees-equalized. Probably if all adjustments are perfect a solid bushing will work but I think the engineers designed the system so it is somewhat self correcting or as the repair manual states " The service brakes operate independently of the emergency brakes and consist of eight brake shoes , four on front and four on the rear, connected by a series of brake linkage which acts not only as an equalizing but proportioning medium." Keep us posted as to how you make out as I am sure several of us are interested and would like to have a solution for repairing the cross shaft.
Delrin and UHMW have very similar characteristics in applications like bushings and wear strips. I’m using the UHMW because when I went looking I couldn’t conveniently find any round stock Delrin in the size range I wanted.
I will follow up on how it goes. I get to make something useful with the radii cutter I bought for the lathe a couple of years ago. If it is easy and works, I could be persuaded to make them available
I believe the UHMW has a better lubricity coefficient than delrin so I would use it over the delrin. UHMW is what is used as sliders on snowmobile track suspension because of its wearability and lubricity. I believe what you make will be far superior to what was originally used.
I have made a complete set of bushings out of UHMW for the cross shaft that I will use on my ”˜32. This was a labor-intensive project. I am conservative and take small cuts with very pass on my lathe. The small bushings that are currently available from the Filling Station and Steele Rubber are what I would recommend for everyone who does not have their own lathe.
I made the small bushings with a “fin” sticking up like the original rubber bushing, and could probably get the time to to make a single one to under an hour, but it certainly would not be cost-effective for me to make them for anyone else (especially if I was giving them away).
The bigger bushings that go on the cross shaft are easier to machine. If I could find a tool-maker who could make a one-pass plunge tool for me, it would be worthwhile. A problem now is that my radius cutting tool requires me to waste more material than the finished part.
I’ve made these with the curvature of the original bushings and do not see how it would be possible to install them (even splitting them in half) without completely removing the brackets from the cross shaft and drilling out or grinding off the rivets.
I’ve done that, and intend to put everything back together with machine screws and nylon insert nuts. I’ll use 12-24 screws and nuts as they seem to be the same size as the original rivets. Another reason is that I don’t want to use the heat required to properly set rivets so close to the new plastic bushings.
In any case, if I can get to the point where I can make these bushings quickly and economically, I’ll make them available for others.
Yes it is necessary to remove the rivets and separate the halves of the supports. Re-riveting the halves back together is not a problem with proper bucking and either an air hammer or rapid blow with large hammer. Have used either to produce secured halves. What I don't like is to have to remove the end brackets and then weld them back on. It is necessary to slide off the bushings and supports, replace the bushings and reinstall on the shaft.
Sorry to come in so late on this thread, but I ordered the rubber bearings (for the frame connection point) for the supports from TFS. It seems that they are somewhat thicker than they need to be. When put together, there is about a 1/4 inch gap between the two halves. Has anyone else had this issue? Should I just trim them up to fit better? Also, I assume the metal sleeve that was in the original rubber bearing should be put back into the new ones so that the nut can seat against it? Thanks. BTW, I had to put my '31 sedan on the back burner for several years but I am back working on it. Life does get in the way sometimes.
Ralph
--------------------------------------------------------- Thanks much, Ralph "Roll Tide"
What is the part number of the part your are referring to. There needs to be room for the lever end of the bracket to move . The inner sleeve is held tight to the frame and the rubber bushing (one piece part) between the sleeve and the lever allows that movement.
I have attached photos so it may be clearer. You can see how much larger the new bushing is and how the two halves of the bracket fit together with the new bushing and the old worn bushing. Also have pic of the bag. I got these new bushings some years ago, and just did a search in TFS and can't find them now. I think I can trim the new bushing down to fit. Not sure the old steel sleeve/spacer will fit in the new bushing or not. Thanks
--------------------------------------------------------- Thanks much, Ralph "Roll Tide"
Trimming slightly may help. When I installed mine I did not take the bracket apart. I installed the inner sleeve and then compressed the bushing with a hose clamp - centered the assembly over the bracket and pressed it in. That was a long time ago and I think I pressed it in using my vise. Be sure to lubricate the bracket and bushing. The bushing needs to have compression tension on it when installed to function properly.
