Spacers between bearings?

[El Gecko]

Thinking about how hub carriers have that little ridge in the middle that separates the bearings...

In BMX we have press-fit bearings too, and it's generally accepted that a spacer between the two bearings is a good thing.

It spreads the side loads between the two bearings, whereas without a spacer only one bearing is taking the impact.

It also lets you torque the cranks down to the correct spec on the spindle, so in effect the whole inner bearing races + inner spacer + outer spacers + crank arms becomes one single unit, and on the whole it's much stronger than other types of setups.

I did the same for my skateboard wheels long ago, and I'm thinking a spacer could help in our RC axle carriers too. Particularly for making the whole axle setup much stronger overall, but also the bearings would last longer, and you could tighten down the axle nut as tight as you want without fear of smashing the bearings or bending a drive pin (once it's all correctly shimmed, that is). Since it's such a thin area to fill up, a few 5mm axle washers would probably be all that's needed, but it's hard to say if the measurements would work out inside the hub carrier (maybe close is good enough?)

Only one way to find out I suppose...

[Willy iine]

Do you mean like shims.. (?)  Shims work great where needed.

[El Gecko]

Yes shims, but does anyone put shims inside the axle carriers, between the two bearings?

I don't know that I've ever seen a manual call for washers there--typically you just press a bearing into each side of the carrier, slide the axle through (with possible shims on the outside being a very normal thing to do), and then it's ready to be installed on the car.

It's an extra step (and extra hardware) during assembly, but I'm thinking it might help prolong the bearings lives while getting rid of any slop in the axles at the same time.

[IoWBasher]

Currently I'm building a M-08 chassis and this uses spacers/shims between the bearings, a number of other manufactures kits I've built over the years also do.

As you say it prevents preloading the bearings if the hex tightens on to the bearing, generally I use metal hexes and shims to achieve the same.

[El Gecko]

8 hours ago, IoWBasher said:

Currently I'm building a M-08 chassis and this uses spacers/shims between the bearings, a number of other manufactures kits I've built over the years also do.

Well I guess that means I need to get out more

All of my kits are pre-1992 and don't even suggest putting shims there.

[svenb]

Tamiya make these spacers already for certain bearing sizes.

53891

[BuggyDad]

My Cougar KR front hex conversion axles are stepped out to a larger diameter between the bearings, eliminating the preload as a spacer would. However this does mean you need a screw on the inner end of the axle to retain it all, which adds a risk of it coming undone. Probably fine but I wonder why designed in this way instead of a spacer between two bearings.

[Cynan]

The SA has these spacers in the hubs between the bearings too.

[SlideWRX]

When I was tightening up the front end of my DT-03, The wheels wobbled a fair bit.  I put shims on the uprights shaft to take up some clearance, but it seemed to cause some side load friction in the bearings when the nut was tightened down.  I created a spacer/shim between the bearings from some plastic tube I found around the house that had the right diameters.  I haven't done the same on the rear hubs because it seemed fairly tight but free spinning, but yeah it would distribute the load a bit better.

[Thommo]

 

Some Tamiya hubs will accept an 850 bearing  inside the centre of the hub..... so effectively 3 bearings inside the hub instead of 2  !

[markbt73]

I understand the design and engineering you're talking about, but RC cars are so lightweight, and the forces involved so small, that I can't imagine it would make a difference.

[c64orinoco]

The M07R chassis uses spacers inside the hub between the two bearings, with shims between the outer hub bearing and the wheel.

[matisse]

Crush tubes. see them on quite a few cars, but it's not a standard thing.

[Honza]

It's quite common in higher end kits - here's  TRF420 manual for example: