Don't like the adverts?  Click here to remove them

Why have a spacer in between two fixed bearings?

Chris

Super Moderator
Supporter
Joined
Feb 24, 2010
Messages
17,937
Garage
Country Flag
great_britain
Ok not cruiser related but I have a small steering hub that takes two identical wheel bearings. They go in from opposite ends and will fit up snug against an internal rib. They aren't taper roller, just sealed ball bearing races. The later model just has one long through bearing.

When I came to knock the bearings out, I had a real struggle as there was a spacer ring in between the two - in other words no knock out slots. I had no choice but to bash away until I made a gap to work with. The bearings were completely toast by the way. No wonder it was wobbly.

Measuring up, it seems that if I put the bearing in without the spacer, they'd be 10 mm apart inside face to face. But then there's this spacer. It's almost the same dia as the middle races so it could transfer load and is also the right dia internally for the drive shaft. Essentially it's like a spare inner race. But - and here's the rub, it's not 10mm wide, it's nearly 11. So what that means is that one or other of the bearings won't seat fully against the internal rib. This makes no sense to me. Oh they'll be snug in there no worries but it means that the internal races will sort of be connected. My only though it that it's a sort of anti crush tube to stop you winding the castle nut up tight and pulling the middles out of the bearings. Yes? No?

This is not a high performance machine and not road legal so I don't have any worries about wheels flying off. It's been running like this for a long time too. I do have the FSM but it makes no mention of this at all. I've spun up some stock in the lathe and made a section 29.95 internal ready to chop into spacers but my question is whether I should go to the exact gap between the inner races or essentially have this slightly oversized third race that effectively pushes the middles of the bearing out slightly.

Yes yes I know that the great god of quads made it like that but I have an enquiring mind. I genuinely can only think that it's to stop the middles being crushed inwards.
 
I'd agree with your anti-crush comment. You can't side load those bearings. Also worth remembering that sometimes designers get a free hand. Whilst it may not require 2 bearings, there is sometimes an overwhelming need for symmetry :icon-rolleyes:. It sounds like the later design with what sounds like a needle roller bearing was thought to be enough following a redesign.
 
I think you're on the money with it stopping people from putting too much load on.

Seems engineers have to take into account ham fisted monkeys that tighten everything until their sphincter twitches.

Sent from my SM-G900F using Tapatalk
 
I certainly think they need two bearings in there. With a ball race there is a touch of the lateral shuffle so it would twist on the shaft. Two bearings cut that to a minimum. It's not a sophisticated set up. Other side was fine, but this one Eeuuch. They were also only shielded on the outside with the inner being open. All to push grease into you say, other than of course there is no room for grease due to the spacer. So it's been running since 2003 on what little lubrication Yamaha put in there. There are oil seals too front and back but they were rock hard.

One bearing from Yamaha was about £30. I went to bearing on line and bought 4 bearings and 4 seals, delivered for £25.00. I'll do the other side another day.
 
Yep, the axial loads on a narrow ball race would be too high for one bearing. The spacer moves the load outwards and so reduces it. I guess you bought sealed bearings so no greasing worries.
 
Don't like the adverts?  Click here to remove them
No no, they are sealed bearings but there are outer seals too. Just like on a Cruiser really. The rubber spring gaiter type things. Went with sealed bearings to try and keep the crap out a little longer. Can't these ever needing changing again.
 
I'd agree that the spacer is an insurance against popping the inners out of the races, but you would have expected the spacer to be machined to the correct space, i.e. 10mm.

That's surely a mystery... :think:
 
The inner spacer should be the same thickness as the outer one and the outer wall of the bearing tapped home against the outer spacer to make sure the bearing is not stressed when the nut is done up.

My friend had an aircraft where there was no inner spacer and wondered why his wheel bearings lasted 3 take offs/landings. Manual said nut torque was 80 ft/lbs so that crushed the bearings. When the brakes failed we found 5 separate faults. No wonder they crash. All fixed and perfect.
 
Yes that's the bit I don't get
I shall drop one bearing in and re measure it all
 
Back
Top