Hmm… perhaps you were not truly loading just the end of the axle. The pipe was making two points of contact. At the end of the axle pushing down, but also 33" into the axle applying an equal force up. I’d have to draw it out, but I don’t think you were getting the proper applied moment on the end of the axle. If you’re setup is still standing can you do the same, but have less pipe inserted into the axle? Or throw a clamp on the end of the axle, wrap chain or rope around it, and hang weight directly at the end?
Both axles were tested under the same conditions, so I think the results will still show that the static deflections will be the same between a soft and hard axle. The experiment wasn’t to figure out what the actual deflection is but to see if there a difference between the soft and hard. Engineering says that there shouldn’t be any difference but many do not believe.
Nonetheless, when I get a chance will redo the experiment, I have a race this weekend. I could probably hang a weight on the end using a hub and bolt the weights to the hub. The deflection will be less but I could up the load to 40#.
I think that it would be best to build something that mounts to the axle hub to keep the distance equal for all measures.
No. I have not spoken to them about axles other than their telling me that they are very popular in Europe. I ordered a bunch so I will ask them. They are really good about explaining things to me in terms I can understand.
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I agree that is the goal. But I don’t think 20 lbs is enough to put the amount of stress to show an actual deflection
That 20lbs has a lot of leverage though being that far from the bearing carrier?
I don’t think it does, because it is also making contact on the interior of the axle. According to Larry 22" of the pipe was outboard and 33" was inboard. So the moment created was being counter acted. Roughly 33% of the load was actually being applied to bend the axle outboard off the bearing carrier.
At the end of the axle we are seeing roughly 20lbf1.8ft[1-(22/33)] = 12lb*ft. So not that much.
It’s been awhile since I’ve had to do a calculation like that so I could be wrong.
My guess is the deflection we are seeing is just enough load to take the slop out of the system.
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I applied 10 lbs and the deflection was half of the 20 lbs. When I get time I’ll do the math. I don’t think the contact inside the axle makes any difference and will also just apply the load thru a weights mounted to a hub.
The intent of this experiment was to prove that whether the axle is soft or hard they both deflect the same amount under a static load. The theory says that is the case and the experiment shows that it is. We really didn’t need to do this experiment because this is very basic mechanical engineering math.
If we can all agree with the above then why is there a difference in axles? And it’s not a placebo effect.
If your weight bar is past the bearing, this isn’t working like you think it should. The weight bar can only go to the outboard side of the bearing.
It’s a relative measurement. It won’t make a difference for what we are looking for but I’ll redo the experiment in a couple of weeks to make everyone happy.
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I was (over)thinking about this yesterday. I wonder if a “better” test would be to have the ends of the axle sitting on vee blocks where the hubs usually are, then apply the load via the bearing carriers and measure deflection at various points
What ever happened to just track testing and measuring with the stop watch??? 
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It’s gone beyond that! We are here to prove Big Karting is out to get us.
But in all seriousness, this is just a bunch of dudes having a thought experiment.
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Kart nerding is best nerding. 
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Can you change the axle in sim?
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@OldFartKarter isn’t trying to mimic the effect in a kart. He’s showing that deflection is not effected. It wouldn’t really matter where he mounted it as long as it was the same for both axles.
I might be able to run a simulated dynamic deflection test in fusion 360. I’d have to make some assumptions but i could do it with say two different types of 4130 just to see if the heat treatment has an effect on damping.
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Do we have a figure for static deflection stationary under driver load .I once did a test with 56lb hung from the centre of a bare . 30 mm axle supported at its ends.Deflection 0.60 mm.
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NikG.Sorry I was really asking if changing the axle was an option in Kart kraft etc.
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I like to approach karting with the KISS approach.
This is way too in the weeds for me.
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