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Old 02-22-2004, 08:25 PM   #7051
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I can mill out some of the bracing on the car to get rid of weight, but then the chassis will flex more...
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Old 02-22-2004, 09:15 PM   #7052
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yeah. Randman did you say your car was 1500 grams when you weighed it. DO you have any light weight parts on the car. Titanium screws... etc

I know you said you have that small futaba servo 9550. I'm ordeing one of those hopefully that should gimme some more space and take some weight off.
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Old 02-22-2004, 09:20 PM   #7053
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Quote:
Originally posted by shortygy
yeah. Randman did you say your car was 1500 grams when you weighed it. DO you have any light weight parts on the car. Titanium screws... etc

I know you said you have that small futaba servo 9550. I'm ordeing one of those hopefully that should gimme some more space and take some weight off.
I do use titanium screws, but no other real weight savers, I weighed that in with 2 Suzuki drive cups, so that propably made up for the difference that the titanium screws made.
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Old 02-22-2004, 09:37 PM   #7054
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After finishing the car nearly two months ago I finally got it on the track at So Cal. I would have to say durability is not a problem. I did not treatt the car very well and did not break a thing. i was having real traction issues though. I now everyone is running Sorex 36's because that is all there is but I just could not find the bite it looked like everyone else had. My set up used the rear tower up front, rayspeed yellow up front, Associated blues in back, the 2 degree toe in block, and everything else according to the socal set up sheet that comes with the kit. My question is I have still not added the inline axles up front or a one way. How much difference are these going to make?
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Old 02-22-2004, 09:40 PM   #7055
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Actually I think 90% of the people at SoCal, including myself, are using both the inline axles, and 1 way bearing. I definately suggest getting them. If you need help, just drop by my pit (the only guy with a red SD)
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Old 02-22-2004, 10:05 PM   #7056
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what are inline axles??
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Old 02-22-2004, 10:16 PM   #7057
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Quote:
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what are inline axles??
oops, I meant inline spindles.
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Old 02-22-2004, 10:36 PM   #7058
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are the inline spindles better for carpet too.?
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Old 02-22-2004, 11:04 PM   #7059
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Quote:
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are the inline spindles better for carpet too.?
They just give the car more steering. I actually took them off when I raced on carpet, had plenty of steering with the foam tires.
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Old 02-23-2004, 06:05 AM   #7060
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Regarding Chassis Stiffness:

The SSG has very good longitudenal stiffness - so it bloody should with 3 WCF decks!!!

However, the lateral stiffness is very poor when compared to just about any other car - the car 'twists' a great deal. The primary reason for this is nothing to do with the car's actual design - but down to dubious material choice. Both the SSG AND the black woven carbon fibre sheets only have 0 and 90 degree laminates -so is stiff in only one direction. The better quality stuff (decent aftermarket chassis conversions etc) has 0, 90 and 45 degrees laminates - stiff in both directions.

The second reason is the use of ordinary button head screws instead of countersunk screws on the upper deck. All the holes where the button head screws have to pass through obviously have to have a clearance. So when the chassis twists, the screws 'hold' in the tweak, as the heads of the screws aren't supported so allow the deck to move and then hold it in the new position.

Regarding tyres:

I don't race foams - it's against my religion to do so - but I've always thought that the profile of a rubber tyre is very important regarding grip roll, whether you're racing a touring car or an off road buggy. Now with foams, they all tend to be flat and square, but with the corners rounded off. Soft sidewalls = lot's of forward traction just look at tyres on fullsize dragsters - super flexy sidewalls!!! Side bite and forward traction aren't the same. And the proper use of camber reduces the chances of roll over too.

Going to a harder compound reduces forward traction, so speeds are reduced thus roll-over is less likely at the expense of some speed.

Going to a softer compound increases forward traction, so speeds are increased. If roll overs are being experienced because of tyres 'digging in' to the track surface, than a softer tyre may actually help. But if the roll overs are occuring because of incorrect car set-up, high CofG, or because of excessively high grip levels inherent to the track surface itself, going softer can't help.
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Old 02-23-2004, 06:24 AM   #7061
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Horatio : button head screws indeed hold tweak after a crash, but has no effect on chassis stiffness (unless your screws are not tightened...).

Both new chassis Mi2 and Pro4 have countersunk head screws, and for both of them I saw chassis tweaked because of that. Last one was this sunday, I checked a friend's chassis on a flat surface (brand new pro4 only 1 week and 2 races old), and it was tweaked. Unscrewed the front top deck screws, screwed the steering post screws (not countersunk), the chassis was flat. Screwed the other screws (countersunk), chassis back tweaked...

I ended up taking the countersunk screws out of the front of the car and using large spacers. Back on the track, the car was much better, now he just needs a better setup...

For that reason, I say : DO NOT COUNTERSUNK the top deck. I always have been against that hype, it's just a thought from racers that it gives a tweak free car.
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Old 02-23-2004, 07:20 AM   #7062
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I disagree entirely - countersunk screws locate far better for any given amount of torque applied. If you hit a car hard enough, it will tweak (or break) - but countersunk screws are less prone than button heads.

The example you gave suggests that the car you were working on simply had holes that didn't line up properly! With button heads it is less critical, agreed, but this is hardly the point I was making.

Countersunk screws are a much better engineering solution, but a more costly one too. It's not hype.

Regards stiffness - the material is to blame. But the screws add to the problem. Whilst they are not directly anything to do with stiffness as such, if they allow movement you'll never get a chassis that is 'solid'. Get an Xray (NOT the tub version ) and an SD SSG side by side and twist the chassis on both cars. Which car twists/creaks/tweaks the most?

Which car has the countersunk screws? Which car has the better quality WCF?

I rest my case
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Old 02-23-2004, 07:57 AM   #7063
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well i'm gonna finally run my black SD and hopefully i won't
have as much issues with it as posted on this page.
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Old 02-23-2004, 08:17 AM   #7064
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Pro4 and Mi2 are two latest cars using countersunk screws, and I saw both having problems with tweaked yet brand new built chassis.

The thing is that indeed the parts have far not enough accuracy and the holes are not located properly. It's the reason why a good car have button head screws, or costs much more than $300 (300 in UK ).

Countersunk is not a better engineering solution, countersunking gives an hyperstatic system which is the reason why pple think it sloves tweak. But it can, (and will for sure IMHO), lead to the problem mentionned above.

It's a hype because drivers asked for it, whereas back a few time ago no car had any tweak issue nor countersunk top decks, because it's nonsense for an engineer, unless you expect very high production cost, not just because of countersunking, but because you'll need better accuracy on a lot of parts (specially on the molded gear boxes for the pro4 and the SD), and that costs a lot.
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Old 02-23-2004, 08:56 AM   #7065
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Yes, I agree that accuracy is more important with countersunk screws. But just about all cars have counter sunk screws on the underside of the chassis - it's not as if they're a new idea

With latest CAD/CAM CNC and all the rest of it, there's no excuse for the major manufacturers to get it wrong. It will always be more expensive though because it requires two operations to produce a countersunk hole, rather than just one as well as a greater degree of accuracy.

Tweak has always existed, but in the 'old days' no one worried about it People were more worried about their 1700 SCR lasting the full 5 minutes!
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