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TJ Koyen
Joined: 03 Oct 2004
Posts: 1413
Location: United States, Wisconsin, Sun Prairie
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 Posted: Wed Dec 08, 2010 9:35 pm Post subject: |
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| Quote: | | I agree that the deflection from the assumed load on the spindles is negligible. But, boy do they make the kart (GP in my case) feel different (better in my case). |
Same experience here.
And that's all that matters to me. Instead of sitting in the pits trying to calculate spindle deflections, I prefer to put a set of 25mm spindles on and see how they feel on track. And there IS a difference in the way the kart feels.
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T.J. Koyen
OKTANE VISUAL - Custom Helmet Paint & Graphic Design
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Mike Goebel
Joined: 28 Jul 2001
Posts: 5765
Location: United States, California, Winnetka
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| Posted: Wed Dec 08, 2010 9:39 pm Post subject: |
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| TJ Koyen wrote: | | Instead of sitting in the pits trying to calculate spindle deflections, |
Sounds like you are ready for F1 
Mike G.
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Dan Haynes
Joined: 17 Sep 2007
Posts: 2371
Location: United States, Pennsylvania, Ellwood City
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| Posted: Wed Dec 08, 2010 10:08 pm Post subject: |
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| Quote: | | Sounds like you are ready for F1 |
is that a new spindle???
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TJ Koyen
Joined: 03 Oct 2004
Posts: 1413
Location: United States, Wisconsin, Sun Prairie
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| Posted: Thu Dec 09, 2010 5:57 am Post subject: |
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| Quote: | | Sounds like you are ready for F1 |
I let my engineers handle the "tuning". I have more important things to do like look good on camera. Oh and driving.
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T.J. Koyen
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Mike Goebel
Joined: 28 Jul 2001
Posts: 5765
Location: United States, California, Winnetka
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| Posted: Thu Dec 09, 2010 9:28 am Post subject: |
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| TJ Koyen wrote: | | Quote: | | Sounds like you are ready for F1 |
I have more important things to do like look good on camera. |
Now you understand!
Mike G.
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Chris Parks
Joined: 09 Sep 2001
Posts: 1504
Location: Australia, not USA state,
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| Posted: Thu Dec 09, 2010 5:51 pm Post subject: |
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| Walt Gifford wrote: | The front end has to have some flexibility.
Gif  |
Really, tell me why.
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understeer happens on road courses and usually is pronounced with a British accent. Push happens on ovals and usually is pronounced through a wad of chew. Other than that, I don't think there's a difference - Jim Derrig
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Walt Gifford
Joined: 19 Jul 2002
Posts: 4289
Location: United States, South Jerrrsey,
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| Posted: Fri Dec 10, 2010 8:20 pm Post subject: |
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If the front doesn't flex enough the inside rear will sit down too soon and you'll have understeer coming off the turn.
Gif |
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Chris Parks
Joined: 09 Sep 2001
Posts: 1504
Location: Australia, not USA state,
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| Posted: Fri Dec 10, 2010 10:57 pm Post subject: |
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| Walt Gifford wrote: | If the front doesn't flex enough the inside rear will sit down too soon and you'll have understeer coming off the turn.
Gif |
So that means that the seat is in the wrong position as the return to centralised steering and the transfer back to all four wheels is not linear for want of a better word. In other words the kart tipped too far and is now suffering from the soft chassis deciding that it did not like to overflexed due to the low spring rate and throws the chassis backward across the loaded diagonal. If it was not so soft this would not occur, the kart should be set up so it tips just enough to unload the inner wheel but not clear the ground.
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understeer happens on road courses and usually is pronounced with a British accent. Push happens on ovals and usually is pronounced through a wad of chew. Other than that, I don't think there's a difference - Jim Derrig
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TJ Koyen
Joined: 03 Oct 2004
Posts: 1413
Location: United States, Wisconsin, Sun Prairie
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| Posted: Sat Dec 11, 2010 12:19 am Post subject: |
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| Quote: | | If the front doesn't flex enough the inside rear will sit down too soon and you'll have understeer coming off the turn. |
True, but I've seen guys run the 25mm spindles and cut 30mm axles to use for front bars and they've been missiles on track. It's hard to get much stiffer than that.
Driving style is a big factor too.
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T.J. Koyen
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Derek White
Joined: 18 Jul 2005
Posts: 70
Location: United States, Ohio, Solon
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| Posted: Mon Dec 13, 2010 12:04 pm Post subject: |
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| Is front spindle size regulated like that of rear axles? Has anyone tried larger spindles? If 50mm is the hot ticket on the rear, maybe it would work on the front too... |
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Chris Brunnemer
Joined: 13 May 2009
Posts: 582
Location: United States, Indiana, McCordsville
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| Posted: Fri Jan 28, 2011 3:45 pm Post subject: |
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| Larry Hayashigawa wrote: | It doesn't make sense that such a small deflection could make a such a difference. Therefore the deflection has to be higher.
I think there is very large moment working on the spindle that is being overlooked. The large moment is generated by the effective cornering force working at the center of gravity of the kart w/ driver and the contact patch of the tire. This moment arm is more like 2.5 ft and the cornering force is 800 lbs (2gs x 400 lbs) . So the moment is closer to 2000 ft-lbs realizing that this moment is distributed between the rear axle and the front spindles. Nonetheless, the moment at the front spindles it is a lot more than 400 lbs x 6 inches = 200 ft lbs being used in the earlier estimates.
A 25 mm spindle is about 4.7 times stiffer in bending than a 17 mm spindle.
Does this make sense?
Larry |
i think i have the answer for you. i threw some crude drawings into inventor and did a stress test on the crude spindles. the spindles were a solid 17mm spindle 150mm long and a hollow 25mm spindle with 2.5mm sidewalls. i dont know the exact length and sidewall thickness but i feel the length is close enough get an understanding. my crude results with 400 pound(1780N) for the 17mm was a max displacement of 2.394mm adding 1 degree of camber not including the added deflection when hitting bumbs. the 25mm spindle tested out to .9372mm and .37 degrees of camber. i used high strength steel as the material. and the point of force was aprox 145 mm out. cut the weigths in half and the 17mm has 1.197mm of displacement compared to the 25mm's .4686mm of displacement.
I warn you though i am relatively new to the stress analysis but i feel that i have accurate results as i fixed one end in solid and applied the weight to the opposite end with the appropriate amount of weight. |
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Chris Livengood
Joined: 24 Jul 2001
Posts: 2432
Location: United States, Pennsylvania, Da Burgh
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| Posted: Fri Jan 28, 2011 4:40 pm Post subject: |
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Tire deflection will of course be at least a hundred magnitudes higher. Why don't we adjust tire pressure by the 100th of psi to change spring rates on the magnitudes you are discussing? I.E. for you theory to explain a difference in perceived handling wouldn't you think we would just adjust tire pressure to achieve the same thing?
Not being argumentative, just inquisitive.
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Chris Brunnemer
Joined: 13 May 2009
Posts: 582
Location: United States, Indiana, McCordsville
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| Posted: Fri Jan 28, 2011 6:16 pm Post subject: |
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| Chris Livengood wrote: | Tire deflection will of course be at least a hundred magnitudes higher. Why don't we adjust tire pressure by the 100th of psi to change spring rates on the magnitudes you are discussing? I.E. for you theory to explain a difference in perceived handling wouldn't you think we would just adjust tire pressure to achieve the same thing?
Not being argumentative, just inquisitive. |
i 100% agree but i just tested just the one variable that people asked about. the 25mm deflects about 2.5 times less. I could make a crude model of each and see how it affects the deflection but i feel like within the small range a tire normally runs in 14ish-20 psi that the deflection will still be the same in comparison to the two types |
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Chris Parks
Joined: 09 Sep 2001
Posts: 1504
Location: Australia, not USA state,
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| Posted: Sun Jan 30, 2011 3:34 pm Post subject: |
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| Chris Livengood wrote: | | I think they are a lot like the 17mm spindles, just 7mm larger. I'm not being cheeky. |
We had some axles run through some very thorough engineering assessments and the minimum size that is adequate to stop deflection is 20mm and preferably bigger. I still have all the drawings here as we were designing a totally new type of front spindle assembly that would blow your socks off with the advantages. One day......
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understeer happens on road courses and usually is pronounced with a British accent. Push happens on ovals and usually is pronounced through a wad of chew. Other than that, I don't think there's a difference - Jim Derrig
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Chris Parks
Joined: 09 Sep 2001
Posts: 1504
Location: Australia, not USA state,
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| Posted: Sun Jan 30, 2011 3:38 pm Post subject: |
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| Chris Livengood wrote: | Tire deflection will of course be at least a hundred magnitudes higher. Why don't we adjust tire pressure by the 100th of psi to change spring rates on the magnitudes you are discussing? I.E. for you theory to explain a difference in perceived handling wouldn't you think we would just adjust tire pressure to achieve the same thing?
Not being argumentative, just inquisitive. |
You could rationally use that argument for a F1 car, most probably more so as the tyre loads would be far greater. It all comes down to cutting the losses. That is why worn bearings and rose joints are replaced, tyre losses would be greater than a slightly worn bearing.
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understeer happens on road courses and usually is pronounced with a British accent. Push happens on ovals and usually is pronounced through a wad of chew. Other than that, I don't think there's a difference - Jim Derrig
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