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Author Topic: Steady, Straight, WOT  (Read 15892 times)
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Peter Jack
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« Reply #75 on: May 10, 2018, 07:12:12 PM »

As a fabricator I've never liked powder coat on racecar chassis just for the stated reasons. It's really hard to remove to do an effective repair and when you do have it all removed and start to weld it liquefies and runs toward the weld from a different area. I've always preferred a good coating of rust paint which is easy to remove and offers little interference with welding when things have to happen in a hurry. Then again I've always been known for more go than show and that doesn't always sit well with some owners.  grin grin grin

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Tman
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« Reply #76 on: May 11, 2018, 03:16:48 PM »

Looking good Marty.
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Mr. Schimstock
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« Reply #77 on: May 11, 2018, 11:38:42 PM »

Thanks Sid.   It may cost me a tiny bit in aero but given the track condition lately I'm sure it will be nice feature to have.  Rather bounce off than dig in. 

Tell me about it. I had that very problem at 2017 WoS. It is a 1/4" thick aluminum plate belly pan from now on.

John


John,

Wow!  That's nasty looking.  How much ground clearance and suspension travel were you running?
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« Reply #78 on: May 11, 2018, 11:43:04 PM »

I'll have to keep in mind the powder coating issues for the future..... obviously too late now.   I went with a light color, silver, to help it show cracks if they should develop.  We do that on test stands at work.  Lighter colors really make them stand out. 
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Peter Jack
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« Reply #79 on: May 12, 2018, 04:15:17 AM »

I really wasn't meaning to slight your efforts. Unfortunately experience is one of the best teachers but she can at times be a little tough on a person. For future reference, if you want a glossy finish a good enamel finish can give you what you're looking for without the annoying side effects and it's relatively easy to hide repairs and changes. I don't like two part paints because they can give off some nasty fumes as well.

Just as an aside, I do use powder on lots of small parts. For those it often works well.

Your progress is looking good and I do wish you well with the project.

Pete
« Last Edit: May 12, 2018, 04:16:51 AM by Peter Jack » Logged
ggl205
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« Reply #80 on: May 12, 2018, 06:50:14 AM »

John,

Wow!  That's nasty looking.  How much ground clearance and suspension travel were you running?

Beginning ground clearance was too low at 1.5" and became a salt plow on the first run. We raised clearance twice more to eventually achieve a little over 2" but that was still too low. All the pounding and repairs eventually compromised the under tray and it folded up on Lyn's last run (180 mph). Fortunately, it held long enough for her "B" license and qualify for long course next outing. Lyn was one of many to get a Spin Pin that meet.

Another contributing factor was the eight brand new front trailing arm rod ends. There was far too much combined stiction to allow suspension to move freely. Even with fairly stiff springs, the first bump compressed suspension and rod end stiction was at least partially responsible for a slow return, if any. Changes for next meet will be to greatly reduce stiction, raise front ground clearance to around 2.5" and put in a 1/4" thick aluminum belly pan that is bolted in, not Dzus fastened.

Oh yeah, I was planning on .500" of front suspension travel.

John
« Last Edit: May 12, 2018, 07:40:43 AM by ggl205 » Logged
manta22
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« Reply #81 on: May 12, 2018, 10:46:43 AM »

John;

One thing that might be contributing to your problem is aerodynamic downforce on your front end. At higher speed the downforce compresses your front springs and the ride height decreases. Try tying a nylon ty-wrap around the rod on your front shocks (as the springs compress the ty-wrap will be pushed further up and it will stay at the maximum travel point). That will indicate how low the nose of your car is being pushed down. You might need a higher spring rate.

Regards, Neil  Tucson, AZ

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Rex Schimmer
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« Reply #82 on: May 12, 2018, 01:06:16 PM »

John, Neil probably hit it with his down force thinking. Flat bottom cars can generate sizable amounts of aero down force which could certainly make the car drop during running. Another thought would be to put some stiff shock snubbers  and cut their length so that at ride height you have your 1/2 inch compression travel before you hit the snubbers. Keeps the bottom off the ground and also doesn't go to full solid suspension.

Rex
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ggl205
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« Reply #83 on: May 12, 2018, 02:41:24 PM »

Neil/Rex:

Thank you both for the suggestions. I am considering a higher front spring rate, maybe even rising rate springs but not too much more than the 350 pounds per corner I have now (front corner weights were in the 275 pound ballpark). I have a front 1:1 motion ratio and may, at some future date, go to a 2:1 rocker ratio. So much salt found its way to my dampers, it was easy to see damper travel of 1" or about twice what I was shooting for.

On the way back home from WoS last year, I stopped by the Darko tunnel. Front downforce is a little over 100 pounds positive at 250 mph so not enough to cause me grief. I am changing a few things around so I may even see a little less positive downforce next time out. But I hate stiction with a passion. It kills almost anything you are asking suspension to do and I knew that going in. I just did not have the time to fix it. I had hoped a few passes down track would loosen them up but it did not.

I will definitely use elastomers on dampers for compression control. Cheap and easy. I will also use rubber snubbers instead of leather belts for droop control. Belts kind of got in the way and stretched some as well.

Anyway, all in the name of vehicle development, right?

John
« Last Edit: May 14, 2018, 08:15:03 AM by ggl205 » Logged
Mr. Schimstock
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« Reply #84 on: May 14, 2018, 11:56:31 AM »

I really wasn't meaning to slight your efforts. Unfortunately experience is one of the best teachers but she can at times be a little tough on a person. For future reference, if you want a glossy finish a good enamel finish can give you what you're looking for without the annoying side effects and it's relatively easy to hide repairs and changes. I don't like two part paints because they can give off some nasty fumes as well.

Just as an aside, I do use powder on lots of small parts. For those it often works well.

Your progress is looking good and I do wish you well with the project.

Pete

No problem Pete,    I took it as constructive criticism.  The company that did the coating also provided a rattle can of paint that is a perfect match to deal with the inevitable and already occurring nicks and dings.  If (and likely when) I need to do any welding I'll just need to pay attention and get it all off and far enough away.
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Mr. Schimstock
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« Reply #85 on: May 21, 2018, 06:50:19 PM »

Finally moved forward after some noodling on how to get the holes through the body lined up with the tabs on the chassis.  Some are pretty straight forward, drill from the inside out.  Others required putting a flashlight on the inside and drilling through the center of the shadow.   Couple more to go on the nose but it's off to a good start. 


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