Hi all,
I am currently rebuilding my A65 engine and have bought replacement layshaft needle roller bearings, along with all other roller bearings.
I have noticed that the closed end original layshaft bearing is different to the replacement bearing. The replacement doesn't have an oil hole and also has less rollers.
Is it normal to fit a new bearing and block off the oil supply? Or should I try and find a different bearing?
Any advice would be appreciated.
Regards,
Wilf.
Hi Wilf,
I recently replaced gear box bearings and had the same questions. I originally purchased the caged needle roller bearing but opted to fit a crowded needle roller as original. I suspect that the caged needle roller is just as good but as the crowded needle roller bearing is available I opted for that. With regard to the hole, the layshaft sits in the gearbox oil so the bearing gets plenty of oil without the hole and this was confirmed by SRM, the supplier of the bearing. This saves having to get the hole perfectly lined up when fitting.
Dave.
Hi Dave,
Thanks for the reply.
I think I will try and get a crowded needle roller with an oil hole if it's possible. I will see what I can find.
I understand that the gearbox is submerged in oil, but was worried that the thrust washer would restrict any oil from freely lubricating the bearing without the oil hole in it.
I presume the bearing should be fitted either flush or slightly below the face, so that the thrust washer can seat against the casing face?
Regards,
Wilf.
Hi,
I fitted the bearing to be only just below the surface of the casing. It is worth spending a bit of time getting the shimming right as this sets the spacing for the rest of the gear box and can make it smoother and more precise. Although there are, I think, three shims available I reduced one down a bit to get the best fit.
Dave
Hi Wilf,
The correct bearing is available in the US, expensive though.
I obtained a crowded bearing and carefully made the hole with a Dremel making sure it was spotlessly clean before fitting.
Best wishes...
I had the same dilemma when rebuilding the A50 Gearbox. I could not find any with the holes in anywhere and even tried the main go-to Japanese manufacturer Koyo here in the UK who said they don't stock them. I then tried an industrial bearing stockist in the midlands and they found a genuine Torrington in the USA at £38 each plus £20 shipping!!!
I worked out that the shaft is submerged so I declined and went with the non-hole type in the end.
Thank you all for the reply's.
That's put my mind at rest as it seems common to fit without the oil hole.
I will carry on with the bearing that I have been supplied.
Many thanks,
Wilf.
Could someone explain "caged needle" vs "crowded needle"? Never heard these terms.
Caged means that the rollers are held apart by a cage of either brass or steel. Can also be plastic on cheaper bearings. The caged bearing will stop the rollers rubbing against each other and causing damage. Crowded rollers mean that they are packed with no spacing. The problem with crowded rollers is when they are subject to high RPM then the rollers tend to bunch up usually on big ends with bad results.
Hi,
It may be easier to google these terms but to put it simply, the crowded bearing is like the rollers in the clutch centre on A65s etc. in that you crowd as many as you can in the space with a bit of room for oil and a tiny bit of expansion. A caged bearing is like the other gearbox bearings or main bearings in that the needle rollers, rollers or balls are held apart by a cage. There are some good pictures on the Simplybearings web site.
Crowded have more rollers but can wear against each other but as there are more of them they probalby take less individual load. The caged rollers do not contact each other but will to some degree contact the cage and there are less of them. There are probably some really complicated explanations bit I will leave those to others.
I would imagine that the loading caused in a big end during combustion is what does them in. In comparison I would think that the layshaft bearing is subject to relatively even load as it spins in the gearbox.
Dave.
Thanks, I did Goggle the terms but wasn't getting too far with it.
I haven't seen a caged type at any of the vendors I use here in the US but this looks like one from Draganfly:
(https://i.imgur.com/PDDWVPel.jpg)
The crowded ones can be a bit "fragile". I had one fall apart on disassembling a Triumph and I
carelessly destroyed one on install. Now I try to press them in hydraulically rather than hammer them in. Heated cases of course.
Hi,
The crowded ones seem to last a long time once fitted but I must admit they do look a bit fragile. Yes it is best to push them in with the case nice and warm. Not having a press I put the bearing in from the inside with a large washer on the lay shaft as a drift and a hide mallet for the force. The bearing went in with almost no pressure and then a very light tap on the shaft without the washer to just set it in a few thou. 650 miles so far and I am confident of many thousands.
It would be interesting to know definitively, which is best crowded or caged needle roller in this application.
Dave.
ps Just found this on the eborbikes.com page re RRT2. "layshaft B-1212OH. Has crowded rollers and the oil hole, both features as per the bearing that BSA fitted. This has about 40% more load carrying capacity than the caged needle roller version J-1212." Their website is not available at the moment so not more info than that.
I have found the attached article regarding the bearing oil hole after some searching online, should anyone be interested.
https://www.classicbritishspares.com/blogs/news/needle-bearing-oil-hole-is-it-necessary
From memory, when I stripped the gearbox on the A50, I did find the hole in the picture above was full of crud. As such, it may be argued that in operation it acts as a sludge trap and if the 'correct' OH bearing is fitted, some of the crud will find it's way in reducing the life of the bearing. You never know, by fitting without oil hole, it may actually last longer!
One good thing about our BSA gearboxes, they let us know when the bearings are worn by singing to us in third gear, then later in second and third and by the time it's singing loudly in first second and third, its time for a strip down!
Happy New Year
Chris