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#Post#: 8122--------------------------------------------------
Playing around with a rear axle
By: Jimr1999 Date: January 26, 2023, 3:38 am
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Morning all.
This is a short video of me playing around with a design for a
rear axle.
The reason I am posting it is because, like all things, it is
probably not new and, therefore, if someone has had a go at this
before, you can point out the pitfalls of the design. All
comments welcome, positive or negative. :) (I always miss
something)
HTML https://youtu.be/J1Dj79GQ_O4
#Post#: 8123--------------------------------------------------
Re: Playing around with a rear axle
By: StefanN Date: January 26, 2023, 5:18 am
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I love the experimentation.
I guess you have thought of this, but I'd make sure the
transition from the 17mm to the larger diameter is well radiused
to minimise stress concentration.
The unknown for me is whether 17mm will be strong enough. The
rear axle takes an unfair share of the weight and it's not
cushioned by a spring, so peak forces will be much higher than
the fronts.
Are the axles surface hardened? If so, machining will have
reduced that.
Certainly an interesting idea. Having four wheels set up the
same* would be an improvement. The oilite bearing approach
works because there's so little rotational movement between the
axle and the wheels.
An alternative approach would be to find 35/25 bearings and use
these front and back - but so far I think we've struggled to
find these at an affordable cost. Or, we make a wheel
specifically for cycklekarts and we can choose the bearing size
- it'll be more expensive than a pit bike wheel mind.
*I have seen people cutting the lugs off the front wheels to
improve the look which would make them not interchangeable.
I've left mine on thinking I might use them to attach fake brake
drums.
#Post#: 8124--------------------------------------------------
Re: Playing around with a rear axle
By: Jimr1999 Date: January 26, 2023, 6:03 am
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Thanks for the reply Stefan, the radius was on my mind, but as I
need a spacer washer between the axle and the bearing face to
minimise the possibility of the outer race of the bearing
rubbing on the axle I could not easily accommodate it. The
Gemini front stubs also are not radiused to the larger
dimension as the bearing seats onto this section so this gives
me a little hope. Driven, they will be using the Kart hub as an
inner support on the 30mm section and both bearings as an outer.
Undriven they will be on the 17mm bit solely but without the
torque forces from the axle so like the front to an extent, but
as you say - with the extra load and no springs.
I worry a little about the stress on it too. But the axle was
almost for nothing, with the hubs and sprocket / brake carrier
and in the interest of experimentation I think I will give it a
go. If it fails, it could be painful. there are a number of
"front wheels coming adrift on a cyclekart" videos around so I
think this is a possibility, although most of them seem to blame
bearings binding and the spindle twisting off the kingpin
carrier.
The axle was not apparently surface hardened as it turned on the
lathe the same all the way through
Jim
#Post#: 8125--------------------------------------------------
Re: Playing around with a rear axle
By: RhysN Date: January 26, 2023, 8:23 am
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I too like the experimentation, and have similar concerns to
Stefan, but have an additional thing for you to consider.
When Graham Hill still had bearings in his non driven wheel, it
was very apparent that under acceleration the car was pulling
one way (towards the "bearing wheel". ) Under braking the
opposite occurred. Only under neutral throttle was the car
running straight. On reflection my ERA so long ago did the same.
I know that replacing the free running bearing with bushes made
this a huge amount less apparent.
#Post#: 8126--------------------------------------------------
Re: Playing around with a rear axle
By: Jimr1999 Date: January 26, 2023, 8:40 am
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Thanks for this Rhys, interesting, I wonder if it was the
increase in friction to the bushes that helped or some other
factor?
#Post#: 8130--------------------------------------------------
Re: Playing around with a rear axle
By: RhysN Date: January 26, 2023, 2:58 pm
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My belief, based on back to back experience, is what I said
previously.
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