Author Topic: # 3838 Vinson / Allison Corvette  (Read 46430 times)

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Offline robfrey

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# 3838 Vinson / Allison Corvette
« Reply #45 on: November 28, 2013, 01:34:25 PM »
Okay. I think I fixed it. Someone please try again and let me know.
I don't understand how my YouTube loader got changed so that the default setting was "private".
Note how much I had to saw at the wheel of this car to keep it straight. Problem was corrected on following run when we realized the car was squatting about 3" and caused the strakes to drag which unloaded the chassis. Removing the strakes did not make the car stable but it helped a lot.
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Offline Peter Jack

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Re: # 3838 Vinson / Allison Corvette
« Reply #46 on: November 28, 2013, 02:00:05 PM »
It works great now Rob. What kind of camera were you using?

Pete

Offline Rex Schimmer

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Re: # 3838 Vinson / Allison Corvette
« Reply #47 on: November 28, 2013, 02:06:14 PM »
Rob,
You look pretty busy!!! Lots of "catching" Interesting with a car that is naturally nose heavy and with the addition of the aft fin work that it was so squirrley, of course it the lower strakes were dragging that could account for some of the wondering. Great job, 276 is hauling a$$.

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Offline robfrey

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Re: # 3838 Vinson / Allison Corvette
« Reply #48 on: November 28, 2013, 02:06:54 PM »
I think it was a go pro.
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Offline robfrey

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Re: # 3838 Vinson / Allison Corvette
« Reply #49 on: November 28, 2013, 02:09:59 PM »
It's too bad it took seven runs for us to figure out what's happening. Sort of burned up tires and everything else getting to that point.
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Offline Seldom Seen Slim

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Re: # 3838 Vinson / Allison Corvette
« Reply #50 on: November 28, 2013, 03:11:34 PM »
I just watched it -- and I agree -- you did a whole heck of a lot of steering for a run down a straight course :-o :-o.  And Floating Island/Mountain seemed to float left and right a bunch of times, too.

Still -- a fun run, wasn't it?  Someday I'm going to drive a car down the salt, just to see what it's like.  That look on your face at the end of the run while getting your timing slip - proved that it's all good. :cheers: :cheers:
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Offline robfrey

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Re: # 3838 Vinson / Allison Corvette
« Reply #51 on: November 28, 2013, 04:59:56 PM »
That wasn't me. That was Ray Vinson Sr. And he is one of the car owners. But you are correct, that's the feeling we are looking for. :-)
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Offline robfrey

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Re: # 3838 Vinson / Allison Corvette
« Reply #52 on: November 28, 2013, 05:09:41 PM »
On some good salt, some more chassis tuning, and a bit more boost, I think this car can go 300mph. Also, the converter failed to lock up on the 276mph run so include fixing that in the list for sure.
When I shift this car, I let off the gas completely as the transmission will over run in the lower gears so it does not disturb the tires. I can still shift as fast as a manual box but I believe this method is easiest on the drivetrain. We are still using the stock Corvette rearend and suspension so anything I can do to make that stuff live, I try to make happen.
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Offline Richard 2

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Re: # 3838 Vinson / Allison Corvette
« Reply #53 on: November 28, 2013, 08:15:55 PM »
Robfrey
Did you have to make any changes to the spindles and hubs to correct the scrub radius with the narrow land speed tires?
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Offline robfrey

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Re: # 3838 Vinson / Allison Corvette
« Reply #54 on: November 28, 2013, 10:02:09 PM »
No. Just got the biggest offset we could get on the wheel to minimize scrub radius change..
I used to driving go karts that purposely have huge scrub radius on purpose to give a weight jacking effect and lift inside rear tire. This big scrub radius does not seem to effect high speed stability. I'm not saying that it should not be minimized, I'm just saying that I don't think it is super important because any weight jacking should be minimal as steering angle changes are so small.
I think the instabilities if this car are strictly aero induced. It is actually rock stable at speeds below 200, then it starts to get just plain evil.
Salt was pretty bad at SpeedWeek but the las two runs I made, I could really feel the end plates of the spoiler really working for me at the higher speeds.
You could be on to something though as I can recall when this car was built, we had to move the rack forward and I'm sure it messed with Ackerman a bit.
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Offline Sumner

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Re: # 3838 Vinson / Allison Corvette
« Reply #55 on: November 29, 2013, 12:06:08 AM »
......I think the instabilities if this car are strictly aero induced. It is actually rock stable at speeds below 200, then it starts to get just plain evil.....

Not saying for sure that is the problem, but excessive scrub radius can result in what you are feeling.  When it kicks in the car can start to dart one way or the other more than is comfortable.  The first time I became aware that it even existed was when some guys told me about it with a roadster where it started above 150 or so for them.  Any idea how much you really have?

That is a great car and the runs are very impressive.  Congrats,

Sum

Offline JonAmo

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Re: # 3838 Vinson / Allison Corvette
« Reply #56 on: November 29, 2013, 02:17:43 AM »
Holy Crap how in the world did he keep that thing going straight.... Great job...

Jon

Offline SPARKY

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Re: # 3838 Vinson / Allison Corvette
« Reply #57 on: November 29, 2013, 08:34:34 AM »
Corvettes are unto themselves-- I know of one that did away with the front ifs and went to a straight axle and another that may as well have eliminated rear suspension to get it to settle down---and both of these were/are running 50 MPH less than you did. 

Sum and I  were just recently discussing Door slams. He made the statement that he didn't think he would want to drive a car that he could not MAJORLY  play with the air at the back of the car over 200.

I agree --I am not brave or man enough to try to push a car into those speed ranges without BIG tail feathers like George Fields and Hooley's studie.
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Offline mxnuke

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Re: # 3838 Vinson / Allison Corvette
« Reply #58 on: November 29, 2013, 09:00:44 AM »
Congrats on that 276 mph..cool video. I seen the car at the ohio mile,neat car ..

Offline robfrey

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Re: # 3838 Vinson / Allison Corvette
« Reply #59 on: November 29, 2013, 09:10:09 AM »
Sum,
I'm thinking that minimizing scrub radius matters more for cars with lots of caster. The next time we have it on the scales, I will turn the front wheels as much that is shown on the video and see what kind if effect it has on corner weighting. The one thing that is helping us are we are just using the stock rear spring so it's still pretty soft.
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