Checking the 4 hyatt bearings from my `24 rearend--I`m not sure of the proper way to measure? The book says 0.500 inch diameter on the bearing rollers, ----1 or 2 thousands wear acceptable....I`ve got a 2 used spares but the existing bearings look pretty good---Any suggestions on picking the best 4 to use? Thanks, Paul
I believe there are also thicker Hyatt bearing sleeves available (or at least shims?) to take up the difference caused by excess wear.
First, Hyatt no longer makes bearings or sleeves.
Get you micrometer out, and have fun. The inner two bearings are usually the best, so I would concentrate on trying to find them. Personally, I've never seen a .500 bearing, but that doesn't mean there aren't any. Your best bet is to order sleeves from Langs. Theirs are made to the print, and are exactly the same material as original.
Measure the rollers in each brg, both ends to check for 'taper' pick the best ones based on wear and also tight cages. jb
Like Larry says, I've never seen one at .500, and I've had some new old stock ones. I would want to see .495 dia., or larger. As others advise, you've just got to measure the ones you have. If you don't have a micrometer, you can buy or borrow a digital caliper. They're fairly cheap these days and good to have around when playing with Model T's.
I, too, have never seen a .500 bearing because Hyatt Never made them!
I once had the opportunity to look at a Record of Change card for the rear axle bearing and the roller specification was (I think):
.498 + or - .002
There have bee SO many times since that viewing that I wish I had made a copy of the document.
Perhaps someone here can provide an image. Bill
This brings up another interesting point. When things are designed today, where there is a clearance fit between a shaft and a bearing, the standard practice is for the shaft to be at the nominal size, while the bearing diameter will be sized over the nominal. For instance, a shaft 1.250 dia., would fit in a bearing 1.251 dia. However, in the Model T era, this was most often not the standard practice. The bearing would measure 1.250 dia., and the shaft would measure 1.248. I believe you'll notice that on T crankshafts as well. Something to keep in mind when determining how much wear an item has seen.
I've rebuilt dozens of rear axle assemblies and have yet to find a .500 roller - .496-.498 mostly.
Whichever bearings you choose - make sure the cages are absolutely tight with NO twisting motion AND don't believe anyone that states you can tighten the cage pins by "peining" NO WAY !!!
Drive it 50 miles & check them again.
I'll take those with loose cages if anyone is tossing them out. I ain't proud.
I've scrapped DOZENS !
There have been plenty of bearings over the years that don't even have cages. Model T ball bearing front hubs are one. older Harley Davidson wheel bearings were cageless rollers. I'm not convinced that a loose cage is a major mechanical problem.
Sorry but ball bearing in a race are not the same as roller bearings. Roller bearings need to stay parallel to the axle, loose cages allow them to twist. Twisting makes more wear on all the parts. There is a reason the cages are tight in the first place.
See my second example.
Gotta agree with Mark here. Twisted, or skewed, rollers will bend or arch over the axle shaft and cause rubbing, rather than rolling, at their ends.
Really though, I don't believe loose cages cause bad rollers. I believe bad rollers cause loose cages. For the outer bearings, the wear on rollers tends to be at the end closest to the wheel. That being the case, the rollers wear to a taper, with the diameters at their one end being smaller than at their other, inner end. Each roller rotates at some given ratio to the rotation of the axle shaft. So, at the outer end of the roller, let's say the axle is 1.062 dia. and the roller is worn to .492 dia. For every 10 revolutions of the axle, the roller will turn 21.6 revolutions. BUT, at the lesser worn, (let's say .496 dia.), inner end of the roller, the 1.062 axle is still turning 10 rpm. The inner end of the roller wants to turn 21.4 rpm. Obviously, the same roller can't turn at 2 different rpm, so what happens? The inner end turns at 21.6 rpm, (faster than it wants to), and advances the inner end of the bearing/cage assembly ahead of the outer end, causing a twist in the cage. That's why peening the cage does not work. Just peening the cage does not eliminate the root cause of the twist. The scenario I offer above can also be caused by taper in the axle shaft, and/or taper in the bearing sleeve inner diameter.
I see the 2ed example of loose roller bearings. With T roller bearings there is a large space between each roller and are about 4 inches long, how close and long are the Harley rollers? Bet they ride in harden races, are closer together and have tighter tolerances unlike the somewhat soft axle and wider spacing in a T.
(Message edited by redmodelt on April 11, 2018)
Yes, they are closer together and shorter.
I read your post, but must admit I didn't take the time to digest it. I'll re-read it later, but you may be right about what causes loose cages.
Thanks. I wish I could have written it using less words