How to attach bearing to axle without sliding?

[flynfrog]

Al welding rod just have a few spares for when you bend it.

[marcush.]

quite interesting catalogue there with stub axles ,flange type bearing housings etc also 5mm versions.maybe a good starting point.

http://www.misumi-europe.com/lang/DE/in ... mplete.pdf

[Izzy410]

Well, thank you all for the reply. okay so i have a general way to follow. the shrinking would be a viable option but the bearings are ceramic. i dont think they do small temperature and big temperature is out of our hand FOR NOW. so we will shirnk only the axle and let it expand back.

how do you expand carbon fibre wheels?

as for your option that the axle turns aswell, that might be a good idea since with that both wheels would move together and limit speed differential. damn, we try so much to sync both side of the wheel when we could have just done that! -.-' okay we can make a sort of tube inside a tube. the bigger tube is just a lining for the bearing and the smaller ones is 2mm that latch to the tyres. we'll try that aswell.

Glue is not a problem if we can get the proper material i think. but the one we use were some sort of superglue that was runny. and it tends to get itself into the bearing. we used more viscous glue like those used to stick shoes together and we couldnt apply JUST enough so it doesnt squeeze out of the gaps and get into the bearing.

Again we have a whole year. so we can try doing anything and we have the money.

Our woods are low quality BALSA. and, in truth -.-' the real car (test car would be made in numbers way before) would have to be manufactured a week or so before leaving for competition to reduce wood natural tendency to warp. we've had problems before. the car lost weight during competition! -.- for some odd reason. and not by a bit. by a whole 3 grammes. we had to ballast it with steel axle luckily.

again thank you very much. very much info. as part of it we do write down and credits those that has help for the competition. any of you that has help and wants some publicity (small time company or anything) please do PM so we can do proper arrangement.

[747heavy]

as for your option that the axle turns aswell, that might be a good idea since with that both wheels would move together and limit speed differential. damn, we try so much to sync both side of the wheel when we could have just done that!!

Why is that? What is the issue with different wheel speeds in your case?
As far as I understand it, you don´t drive the car via the wheels.
They just roll at any speed, they see fit.
Not sure what the problem is.

If you connect them via the axle, you will need to pay attention to the diameter of the wheels, as they are foced to run at the same revs (rpm´s) now.
If you have a difference in diameter, you may create a steering effect (car pulling to one side) or additional friction.
But I think, that should be manageable from a production point.

....and we have the money.

That´s allways a good start and will help a bit

[strad]

Go to this site: http://www.emachineshop.com/
Download the CAD design software..use it to draw up a miniature stub axle with threaded ends which can then use small nuts to hold the wheel on.

[tok-tokkie]

I am busy making a pendulum clock. With 12x60=720:1 ratio between the drive weight & pendulum escape wheel it is critical to reduce the forces and inertia of the escape wheel. I use 2mm shafts running in bearings (not ceramic until I have got everything finalised). I use Loctite 290 (cat no 22088 formerly 29031 it says on the container). It is penetrating grade. Very fluid. Assemble the shaft & bearing. Shaft vertical, dip sewing needle into Loctite & hold it to the bearing/shaft interface. Loctite moves by surface tension then creeps in under capillary action. make certain none has got into the ball area - happened to me & I struggled to understand what was wrong with my clock. Easy to dismantle if you heat it with paint stripper air gun - be gentle as you do it.

I also use 2mm shafts elsewhere where i needed to reduce inertia as much as possible. I replaced solid 2mm rods with stainless steel hypodermic needles. They come in non metric gauge sizes. The nearest is 14 gauge = 2.1mm but you could reduce that with wet & dry paper spinning the needle in an electric drill. Very light and stiff.

It is an advantage to spin the shaft as against the outer race of a bearing if you are wanting to limit the friction. The circumference of the inner race is much less than the circumference of the outer race so in 1 rev the balls roll much less when it is the inner race that is rotating.

[Izzy410]

as for your option that the axle turns aswell, that might be a good idea since with that both wheels would move together and limit speed differential. damn, we try so much to sync both side of the wheel when we could have just done that!!

Why is that? What is the issue with different wheel speeds in your case?
As far as I understand it, you don´t drive the car via the wheels.
They just roll at any speed, they see fit.
Not sure what the problem is.

If you connect them via the axle, you will need to pay attention to the diameter of the wheels, as they are foced to run at the same revs (rpm´s) now.
If you have a difference in diameter, you may create a steering effect (car pulling to one side) or additional friction.
But I think, that should be manageable from a production point.

....and we have the money.

That´s always a good start and will help a bit

Friction differential. we cant get the two wheels to have the same amount of friction because of minute things. like one side has more friction than the other or something like that.

it drags the car just a bit, the whole length of the track and the car can displace from straight trajectory like 6-9 mm. which is to us. a major change. syncing them would definitely fix this issue abit. tho, putting bearing on the axle is a new revolution that no team has ever tried as far as im concerned. they think moving axle is moving alot of mass. which is kinda logic. but we can get a tyre sequence that is very light.hmmmm okay we'll take this into consideration.

now to sell the idea to the university we're working with. and the whole team

there's another thing i want to ask but i'll post pictures along with it. cause it'll be a bit hard to understand with words. but that'll be done in a few hours. im off again -.-' at least real time engineers get paid for this we have school on top of learning this

but thanks alot!

[xpensive]

The way we wouuld do it is to ask the supplier for a tapered bore on the inner race to match an equally tapered shaft.

But if that is too much, I would go for a larger bearing id and a tapered sleeve between bearing and a tapered shaft,
alowing the bearing to take axial loads as well as radial such without the sliding friction between outer race and clip.

[747heavy]

Thanks for comming back to me and explaining your reasoning Izzy.
I see where you are coming from now.
Tok-Tokkie made some good comments IMHO and just to compliment his post, you may find some useful informations here.

As for the thought, that you need to accelerate the axle.
Yes this is a valid argument IMO, but on the other hand, I think that the inertia of the outer bearing race and the roller cage is higher then the inertia of the axle.
Especially if you use a hollow axle/tube.

One would need to calculate it with the correct mass and radius in question, to be sure.

So maybe you are onto something here, which is worthwhile exploring in greater detail or testing.

Good luck & keep us posted

[Izzy410]

Thank you.

so for now our team would go ahead with two particular design and test it out.

1st. A design of normal setup plus speed ring
Things to overcome.
slipping of tyre and outer bearing race.
same rotation speed/force


2nd. rotating axle assembly.
Things to overcome.
Higher mass.
New setup and body build.

It'll take some time before we can acquire a test bed. so please be patient in waiting for the results.