Axle support bearings

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jarndice
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Axle support bearings

Post by jarndice »

Everyone with a Heng Long Tank knows how difficult fitting axle support bearings can be. Ensure the gearboxes are firmly located in the hull then when she is not looking place the hull in the ice box of the freezer, if she does not find out you may be alright for hot meals !! In the morning you will need a hammer, a socket, big enough to fit over the bearing and allow clearance for the axle, place the bearings on the hot plate of the oven, NOT SO HOT THAT YOU GET BURNED, Just hand hot, remove the hull from the freezer and lightly smear lithium grease on the axles,support the gearbox with one hand, place the bearing against the end of the axle, tap the socket with the hammer and the bearing will slide straight along the shaft. shaun
I think I am about to upset someone :haha:
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ruben2005
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Re: Axle support bearings

Post by ruben2005 »

:wave: thanks mate :thumbup: :thumbup: :clap:
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Blitzmgg
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Re: Axle support bearings

Post by Blitzmgg »

Tighter than a moles eye lid me thinks ;)
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SteelBird
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Re: Axle support bearings

Post by SteelBird »

jarndice wrote:Everyone with a Heng Long Tank knows how difficult fitting axle support bearings can be. Ensure the gearboxes are firmly located in the hull then when she is not looking place the hull in the ice box of the freezer, if she does not find out you may be alright for hot meals !! In the morning you will need a hammer, a socket, big enough to fit over the bearing and allow clearance for the axle, place the bearings on the hot plate of the oven, NOT SO HOT THAT YOU GET BURNED, Just hand hot, remove the hull from the freezer and lightly smear lithium grease on the axles,support the gearbox with one hand, place the bearing against the end of the axle, tap the socket with the hammer and the bearing will slide straight along the shaft. shaun
I supposed you would show us how to install the axle support with bearing onto the Tiger 1's hull... :O
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Jay-Em
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Re: Axle support bearings

Post by Jay-Em »

It’s the “ Industry Solution” and works for sure. Done a comparable, but inverted, thing with bearings for my motorcycle. Putting bearings in the freezer, especially wheelbearings, is usually a must.

What also works is simply run the gearboxes and press a 600 grit bit of wet-sand sanding paper on the shaft and gently sand the length of the rotating shaft. Try-fit the bearing, repeat, until it fits snugly, but without slop.
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Son of a gun-ner
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Re: Axle support bearings

Post by Son of a gun-ner »

Right. . . .

If you need such extreme measures (heating/freezing/big hammer) for fitting such small delicate precision roller/ball bearings, then the shaft is NOT, I repeat, NOT the correct size for the bearing.

All bearings are manufactured with a tolerance, some tighter than others, especially with tiny ones.

If you were to force on a bearing, even by cunning means, when those materials get back to normal temperatures the bearing will end up dangerously tight within its tolerance limits. Also the bearing can crack under the strain.
Also if the bearing is greased packed, the grease could end up too thick for said tolerances. Bearing tolerances are calculated with the correct grease in mind. Which also accounts for a normal use temperature range, it's the grease and tolerance that defines that.
Therefore, heating and freezing bearings can have a detrimental effect on the grease if it isn't designed to take those temperatures and can break down or run out.

As for using anything to hit/force a bearing on a shaft or in a hole, ONLY push/hit/put force against the race (race = inner or outer ring/ball guide) that is fitting against the object it is fitting in/on. Failure to do so WILL put flats on the balls, and dents in the races.

Therefore, get the hole or shaft the correct size for the bearing, but not a sloppy fit.

One last note, some bearings are designed for a tight fit like car, bike and washing machine bearings etc, not really so for these tiny ones.

Have a nice day :wave:
Last edited by Son of a gun-ner on Thu Nov 29, 2018 1:26 pm, edited 1 time in total.
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yagen
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Re: Axle support bearings

Post by yagen »

Hi guys,

I seem to be lucky once. The bearings I got fit smoothly on the output shaft without being wobbly.

As for the cool / heat method:
If you want to avoid marital problems you could use cooling spray. Be sure to use the industrial strength spray, not the medical one. It is cheap and reaches temperatures of up to -50°C. Furthermore, the spray can be applied directly where you need it. No need to freeze the whole lower hull.
Heating parts can be done safely using a hot-air gun (a hair dryer on steroids). Be sure to use one that allows setting the required temperature. Usually, they support a range of 50 to 300°C.

In my experience, this is an easy, safe method to cool / heat parts and avoids unnecessary strain on other parts. Freezing the complete gearbox can be dangerous as the axles, bearings and cog-wheels are usually made of different materials, thus shrinking differently when cooled. This might damage the gearbox, so be careful.

Hope this helps.
Regards,
Reinhard
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Son of a gun-ner
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Re: Axle support bearings

Post by Son of a gun-ner »

I have freeze spray, I use it for plumbing :thumbup:

To be honest, when it comes to small bearings, I really wouldn't recommend heating or freezing. If the bearing won't fit using "reasonable" force at room temperature, it doesn't fit, and it wasn't designed to fit any tighter, especially if it needs brute force to fit even after heating.

Bearing manufacturers give shaft and hole tolerance limits for their bearings for a reason, and virtually none of those limits are the same size or bigger/smaller than the shaft/hole they fit on/in.
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yagen
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Re: Axle support bearings

Post by yagen »

Hi Son of a gun-ner,

I fully agree with you. :clap:
However, in my case the bearing slides with little force once on the axle. To fit it on the axle is the problem. The first two or three millimeters require some force (it can still be pressed on using the hands, no tools needed). In this case, the bearing, when warmed, should slide on the axle with no force at all.
Everything else means, as you correctly stated, a hint that the tolerances are wrong.

Thanks for clarifying my previous post. :thumbup:
Have a nice time,
Reinhard
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Son of a gun-ner
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Re: Axle support bearings

Post by Son of a gun-ner »

Thank you Reinhard.

My message wasn't directed at you as such.

I thought I would reiterate my point about overly stressing bearings.

Usually shafts are smaller than the bearing seating to aid fitting, we don't have that advantage. And as the bearing doesn't sit right at the sprocket end of the shaft, there is no real problem if the shaft is a bit smaller at that point. Although it may be a little lose in the sprocket.

I've fitted bearings in numerous applications and even made bearings of various types, from hydrogen bearings where the slightest touch from a bare finger would destroy the bearing surface to giant hand scraped shell bearings not unlike the ones used on a ships propeller shaft. And I've used some of the smallest ball races in "my other hobby" and only in very rare specific applications have I ever used any form of heating or cooling to fit any.

Regards.
Mick.
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