Gravity Racer, part IV

Chris Kouba

Supporter
Today was test day #1. I would call it successful. Nothing broke, everything ran like it should, the brakes worked, the suspension was fantastic(!!!) and there were no crashes. All in all, it was pretty drama-free.

In the past three years, the pavement has deteriorated quite a bit, so on pass #1 I ended up with a pinch flat when the L front went into a hole and smacked the lip of its exit at ~50 MPH. Pulling and patching the tube went well, and this time Bill and I walked the hill before climbing back in to tow back to the start. We were able to identify a fairly hazard-free line to miss all the bumps, but it wasn't ideal from a racing/top speed perspective.

This next run went well, much more smoothly, but following the specific hazard-free line vs the ideal "free-fall" line yielded a significantly lower top speed. This was despite the wheel well covers we fitted to the front wheels.

After a few tweaks to the bodywork and hauling back up the mountain, we had another good clean pass. We had a spectator show up who took some pics as we did our fourth run, so I am looking forward to seeing how those may have come out.

Where the rubber hits the road, all but the one weird pass was over 50 MPH, including a new top speed of 53.9 (SO close to 54...). Obviously, the data isn't quite statistically valid, but it certainly is encouraging. I think with spoke covers, better wheel well covers, a rear wheel fairing, and some additional massaging of the bodywork, this should be a record-contending car. I am also thinking about just a little bit more weight.

Sorry no action shots, I was busy and Bill was focused on me. Hopefully some will show up in a bit from the new friend we met today.

Prepping for run 1:


In the shade, waiting for tow back:
 

Chris Kouba

Supporter
No Disc's brakes on wheels, just a 'drag pad'onto road surface under car, hand lever controlled.
That's a hard no. The blue and green car had one and it was atrocious.

These are mechanical calipers and they retract well. They do not rub the rotor unless they are applied. I did try some hydraulics to start with but they had monumental amounts of residual drag.
 

Chris Kouba

Supporter
One more note from yesterday. I sat in it with the "finished" bodywork for the first time yesterday while wearing a helmet and was a little disappointed. Even with a glove on, there is enough room between the top of my helmet and the underside of the canopy that I can easily fit my hand in the gap. Makes me feel like I may have made it an inch or so too tall.
 
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Neil

Supporter
One more note from yesterday. I sat in it with the "finished" bodywork for the first time yesterday while wearing a helmetand was a little disappointed. Even with a glove on, there is enough room between the top of my helmet and the underside of the canopy that I can easily fit my hand in the gap. Makes me feel like I may have made it an inch or so too tall.
Chris, when I built my car I built a roll cage that was just large enough to fit me. When the rule book specified new SFI helmets, they were so much larger that the top of my helmet was above the roll cage. I had to build a new seat so that I could scrunch down and meet the rules. A couple of inches is OK.
 

Chris Kouba

Supporter
Neil - Understood, and I appreciate the value of the space/clearance, but it would make a pretty big "marginal" difference.

Bill and I got an email from the spectator who showed up, Dana. He does some photography and although he was only around for one pass, he was kind enough to send us the pics he took. He got a nice one of Bill and me:



He wasn't quite sure what to expect, so his settings weren't good for clear, crisp shots, but I do like the artistic qualities of this one:



I've been working on some more robust wheel well covers and to close up the belly pan:



And I figured out a way I was happy enough with to close out the tail cone as well (still needs its final segment):



Still have a massive amount of bodywork to knock out and then get it painted, but the results are encouraging and I am looking forward to the next time on the hill.
 
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Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
The body is coming around quite nicely and the whole package is Looking really good Chris!
Any idea of the racer’s current weight?
 

Chris Kouba

Supporter
Thanks Randy, I am quite liking it.

Weight is FR/FL 55# each, Rear 65#, total of 175#, plus or minus (read: measured with $10 mechanical bathroom scales).
 

Chris Kouba

Supporter
OK, now the cart looks a bit like a 917 Langheck! Very cool!
After being at a loss for what I was going to do for a livery, it suddenly came to me over the course of the last week...

Current progress:


I'm not original, but I think it looks great on the shape.

The mirrors will have covers over them to fair the lines back into the side pods. That is why there is black on the pods.
 

Neil

Supporter
Chris, how about adding "Moon discs" over the wire spoke front wheels? They should reduce drag a bit.
 

Chris Kouba

Supporter
Neil- Absolutely. They have been standard practice on all our prior builds and they will be installed on this one too.

In our testing, we found them to give a full extra 1 MPH over our mild gradient 0.4 mile test hill where we were topping out around 40 MPH. This is our straight test hill with a very consistent line and minimal variability. They do good things.
 

Neil

Supporter
Neil- Absolutely. They have been standard practice on all our prior builds and they will be installed on this one too.

In our testing, we found them to give a full extra 1 MPH over our mild gradient 0.4 mile test hill where we were topping out around 40 MPH. This is our straight test hill with a very consistent line and minimal variability. They do good things.
That's why you see them on so many cars at Bonneville and El Mirage.
 

Chris Kouba

Supporter
Yep. Was never a question on this build.

Last pic for today- where I ended up calling it a night. Side pods roughly attached, mirror fairings fitted. Going out with the wife for the evening but pretty happy with the progress for just one day at the beauty salon:


Still needs some bondo work for the tail pieces, so that's the bridge to cross tomorrow.
 
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