OT: Angular Contact Bearings for Right Angle Gearbox?

[nickel-city-fab]

Ugh. Glad you got it fixed anyway. Never seen one with the gear box integral. Makes sense to just fix it as is, then.

[The Metal Butcher]

First of all, I'd like to thank everyone for their comments.

Willing to bet the original bearing seats are pounded out of size and shape tolerances. Frankly I would start looking for a new box altogether: https://www.surpluscenter.com/Gear-Reducers/Gearboxes/

Unless you're *really* looking for a project on a budget.

That sounds like a ton of work for no gain to be honest. The gearbox is integral to the tiller. Everything mounts onto it. It would be a couple weeks worth of work for me to fit something else in. I'd stick a lot of bearings in before doing that.

Bearing pockets that I see oversized (these are always in aluminum) are from improper preload. Less likely in steel, though, and I assume this is steel?

Make sure all of the parts are actually there. For instance, in the BMW axles I work with there are spacers for the inner races that allow you to tighten them together firmly without overloading and also help maintain bearing alignment. Without this spacer, it can be too tight without load and/or too loose with load, but someone who didn't know how the system works would never know the spacer was missing. Most of that addresses tapered bearings but we have spacers on ball bearings as well.

Cast iron. No, not wallowed. Dad got a second one of these as a parts machine. 16 out of 16 bores were oversized between the two boxes (the ones on the side, not the angle box). The bearings in the side gearbox are 100% radial load, with massive bearings given the load, short beefy shafts, and since they're bored in one shot, there is no misalignment. The holes were round and smooth. It's simply a case of them being bored oversize.

Not all China stuff is cheap in qaulity or cost,some is for sure but buying Genuine John Deere or Case New Holland parts these days including bearing a lot are Made in China and aren't cheap to buy.

Now that's true. In this case, the other 6207 bearings in the tube felt kinda gritty and just in general low quality. I bought some imported PGN R12 bearings for the Sidney and they are fantastic. Dead nuts on dimension, very smooth rolling and high quality grinding. I'll be looking for more of their stuff.

Pics could change that.

I don't know what you can make out from the picture other than a lot of swarf. I'd need a macro lens to get in any closer.

---

I showed the thread to dad and he made the decision just to get a non-chinese 6207. He installed it and was more careful with the shimming this time, and moved it out some. It had a minor catch before but could still easily be turned by hand, but he spaced it enough that it didn't catch at all. It works now and seems to be doing alright.

The three causes I can see for the issue (or a combination of the three) are:

1. A bad bearing that is too soft.
2. Gear spacing was too close causing binding
3. The driveshaft was right at the limit of being too long. It's possible it bottomed out and crunched the bearings inward inducing damaged which caused it to fail. I noticed the shield on the inner bearings was pushed inwards which supports my theory. The driveshaft has since been cut shorter, and the other bearing was replaced too.

[wierdscience]

Was the part diagram from the internet bearing seller a Yanmar parts diagram? It's worth doing a little digging to see what the factory had originally intended. With the impact forces of a tiller I would expect some sort of preloaded bearings. Especially to control the fit of the gears, too. The ones I'm familiar with have a tapered roller on the working end and an ac bearing on the other. There are shims used to set both the bearing preload and the gear position. A snap ring keeps it all in place.

This, and it's possible that the mfg originally used max type bearings, which will handle greater radial and thrust loads than a common light duty 200 series.

[Blouwildebuffel]

I work on a lot of 90 degree angle boxes on industrial equipment drives. Some are small, smaller than a shoe box, and run at under 1000 rpm, and most have A/C bearings, but some with little side thrust have good quality deep groove bearings. German designed equipment, works fine without A/C bearings

I replace perfectly fine bearings as part of a routine maintenance schedule, so no damage to seats or shafts yet and even using the same bearing number from the same manufacturer I almost always need to use different shims to get the right "feel" again. Proper adjustment is critical for long service life

OT, I not at all saying the OP did this, just for entertainment, but I saw many angle boxes fail. Got one in now that they claimed I must repair under warranty, but luckily they brought me the driveshaft as well to balance and I saw heavy hammer blows on the outboard side. Bearings was obviously damaged from hammering on the shaft. Got one in that had failed after less than a week of running, later found out the apprentice tried to be cute, took all the FAG bearings out of the packaging and got the pairs mixed up without telling his artisan. One box failed because they used a single lip seal in a double lip application and water got in the box. One was filled with grit, and I later learned while the bearings was laying open on a bench one of the boiler makers was grinding right next to it, grease was like cutting paste. Shims was left out on one, was so tight you couldn't turn it by hand. I also got some in that instead of heating the bearing with a bearing heater and just slipping it over the shaft, they banged it on with a 4 lb hammer. Low oil level, dropping oiler pipe in the sand, heating with O/A torch to remove a broken bolt with bearings installed, mixing gears from different boxes and so on. I got the work on contract because their in house people stuffed up so much, so I'm smiling

[Tundra Twin Track]

[QUOTE=The Metal Butcher;n1881874]Hi all.

However, he's a notorious cheapskate and uses Chinese bearings on everything.

Not all China stuff is cheap in qaulity or cost,some is for sure but buying Genuine John Deere or Case New Holland parts these days including bearing a lot are Made in China and aren't cheap to buy.

[AntonLargiader]

...Every single bearing fit in the secondary gearbox was loose by at least 0.001. The case off the other tiller was worse, at nearly two thou. You could spin the race in the bore no issue. I realize under load that's unlikely, but it's bad practice. We used bearing retainer on every single one. I am quite underwhelmed by the quality.

Bearing pockets that I see oversized (these are always in aluminum) are from improper preload. Less likely in steel, though, and I assume this is steel?

Make sure all of the parts are actually there. For instance, in the BMW axles I work with there are spacers for the inner races that allow you to tighten them together firmly without overloading and also help maintain bearing alignment. Without this spacer, it can be too tight without load and/or too loose with load, but someone who didn't know how the system works would never know the spacer was missing. Most of that addresses tapered bearings but we have spacers on ball bearings as well.

[johansen]

yes, go with angular contact bearings but, do something to preload them, even if only a few stiff wave springs.

you need preload to distribute the force properly onto more of the balls. secondly, the bearing race needs to be constrained so as to distribute the force properly. a loose fit with bearing retaining compund may be good enough.. or maybe the bearing is missaligned within the sloppy fit?

a 6307 or 6308 bearing handles the entire thrust load of the input helical gear shaft in a certain toyota truck transmission. i know this because the owner of one kept driving it even after 4th gear went out and he gave me the transmission to take apart.

4th gear went out because the 6308 bearing extruded the inner race a full 5 mm and the splines to shift it into 4th no longer made contact, and he was driving it... in all the other gears, with the input helical gear (20mm wide) making 75% contact.. until he blew it up. .

the helical gears were about 3 inch diameter and perhaps a 45 degree helix angle. so, you can do the math on how much thrust load there was.

anyhow, i don't think the 6207 bearing should be failing but until you know why, either install a 7207 bearing or put tapered rollers in it, preloaded.

[nickel-city-fab]

Based on the above, I should clarify something.
The reason for the above mentioned issues are the "Importers", not the Chinese people or " some" of the factories
These importers go to China and try to get the cheapest product to sell to make their money. Quality is not on their agenda
This is a replay of the Japanese products in the 1960's where the same thing happened

Rich

100% agree.... and you've no idea how it ticks me off, keeping me up at night shouting at the walls

[tom_d]

Was the part diagram from the internet bearing seller a Yanmar parts diagram? It's worth doing a little digging to see what the factory had originally intended. With the impact forces of a tiller I would expect some sort of preloaded bearings. Especially to control the fit of the gears, too. The ones I'm familiar with have a tapered roller on the working end and an ac bearing on the other. There are shims used to set both the bearing preload and the gear position. A snap ring keeps it all in place.

[Mcgyver]

Shouldn't the gear provide constant thrust force? Nothing will ever force it inwards.
l.

thats a point. I've only ever worked with them in pairs so was may be stuck in rut on that thinking. If the force is always from one direction, perhaps one would work. Room for some belleville washers? or maybe that's just me clinging to my must preloaded past

[Rich Carlstedt]

Based on the above, I should clarify something.
The reason for the above mentioned issues are the "Importers", not the Chinese people or " some" of the factories
These importers go to China and try to get the cheapest product to sell to make their money. Quality is not on their agenda
This is a replay of the Japanese products in the 1960's where the same thing happened

Rich

[Rich Carlstedt]

Guess I am the only one here that has run into bearing quality issues with bearings made in China.
I don't care what it is, I will not and have not ever bought a Chinese bearing !
I have rebuilt things for my friends--since I have a shop
Friend had a trailer that needed wheel bearings and packing. He came over with the "new A/C bearings"
What crap, they never finished grinding the roller surface ..you could see the lines ! ( and uneven height ) .".they were cheap" he said
I handed them back to him and told him to buy some good bearings. he had 4 cones and 4 cups ....two cups were crap.
Another time a friend had a Drill Press that needed new spindle bearings and he bought bearings based on number in part list.
One ball bearing did not fit the quill---it was loose..so he wanted to fill the 2-3 thou clearance with Loctite..
No !, you take it back to the place you bought it and send it back to China .. can you imagine...the OD was under-size !

Then another friend was rebuilding his Model A Ford tranny and I told him to get some SKF bearings and he said he had ordered a rebuild kit from some dealer
You guessed it, the bearings he got were Chinese and he had to flush one of them as it was "gritty"..but he used them ?

so when the poster says that a bearing failed immediately, I just shake my head- perfectly believable
I am sure they can make good bearings, but don't export those, only rejects
Rich

[nickel-city-fab]

Willing to bet the original bearing seats are pounded out of size and shape tolerances. Frankly I would start looking for a new box altogether: https://www.surpluscenter.com/Gear-Reducers/Gearboxes/

Unless you're *really* looking for a project on a budget.

[ikdor]

I'd say if the parts diagram shows a 6200 series bearing, then that is exactly what is needed. Even though an AC bearing is a "better design", they are about five times more expensive for the OEM. There is no real technical reason for them to be more expensive, but 6200 bearings are made by the millions on fully automated channels. AC bearings are manufactured orders of magnitude less and that shows in the price.
The 6200 bearings have about 20% of the radial capacity in the axial direction if I recall correclty, so that 5kN could be enough for this application to have decent life. A few years ago there was even a low cost car that used two DGBBs in the rear wheel to save cost. That is really pushing it.
Igor

[J Tiers]

A sloppy shaft fit can cause other problems as the shaft slams around.

A tight gear alignment also causes problems, better it is loose than tight.

The combination can lead to some interesting things happening in terms of jams and binding.

Sometimes with old stuff, a "correct" installation is not easy or perhaps possible. A loose shaft is one type of "improper" assembly, although it is not easy to avoid without some significant work that may not be worth the effort.

A bearing with loading groove, can easily be installed in the "low thrust" direction without that being noticed. can rapidly become metal scrap if the thrust is significant in the wrong direction. No clue if that one has the feature.

What can you totally eliminate as impossible? When you answer that, go check for it.............!!