1300 Kg Track SUPRA project

josbeat

Supramania Contributor
Jul 31, 2010
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hi! yes it is amazing. believe me.

in the Supra, using both chasis rails is easy to do the flat floor with some riveted nuts but the exhaust must to be very well done , with some oval parts and closing it to the chassis so it must to be used a good heat shieldling like this
https://www.ebay.es/itm/Heatshield-...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

allways is possible to use spacers to lower the floor sheets to get more space. in the middel to the gearbox suport and at the back with a pair of aluminium plates here and there.....
i am not using spacers but i was thinking to use it before, not using spacers because i am lowering the car a lot using a low profile slicks and semi-slicks with a hard springs.

regards!
 
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Piratetip

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Piratetip could be the vibration i feel at high speed the driveshaft critical speed problem??
my driveshaft turn mutch more revs than most because my rear diff ratio is 5.29 .

Have you used the calculator I created yet to see where your 1/2 critical speed is with your driveshaft / final drive ratio / transmission ratios / wheel size ect...?

I tried estimating with the limited amount of information you gave but its probably not accurate.

I would guess you are hitting 1/2 critical speed @ somewhere around 6,700 - 6,900 driveshaft RPM.
 

josbeat

Supramania Contributor
Jul 31, 2010
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spain
Have you used the calculator I created yet to see where your 1/2 critical speed is with your driveshaft / final drive ratio / transmission ratios / wheel size ect...?

I tried estimating with the limited amount of information you gave but its probably not accurate.

I would guess you are hitting 1/2 critical speed @ somewhere around 6,700 - 6,900 driveshaft RPM.


i am waiting to know the driveshaft wall thikness and the quality of aluminium . they dont have any information about it in the web.

uhmmm if the engine have 10.500 rpm rev cut and the 4th gear is 1:1 ratio....the driveshaft will rotate at 10500 rpm but in 5th will be more and in 6th will be over 12000 rpm !!!!
i been looking and " i think" that the critical speed could be arround 11.000 rpm of my Driveshaft looking the chart of PST company , i had one of those from that company before and the ends are welded but the one i have now the ends are riveted to ensure less material fatigue with the welds, the rest looks same.
i have one in carbon fiber that can be trimed to the new distance and looks like those have highers critical speeds yes?
thanks for the helps.

http://pstds.com/critical-speed-chart/
 

Piratetip

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What are your tire sizes to determine wheel diameter?
Also what vehicle speed do you typically notice the vibration?
This could help pinpoint where its coming from.

Easier to back calculate driveshaft RPM from wheel diameter and final drive ratio.

Carbon fiber will pretty much negate any issues with critical speed for your length driveshaft.
 

te72

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Mar 26, 2006
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Thanks for the info on the flat floor mounting, it confirms what I was thinking. I have a welder and I'm not as afraid to use it now as I once was, I think I can do this, if I can come up with brackets that I feel will keep the sheets on the car. The oval exhaust is something I'm considering as well, simply to allow a flat floor, because round tubing just isn't going to cooperate with that idea haha. Plus, considering moving the exhaust exit to the right side of the car, as opposed to the left, so I can relocate my oil tank to free up some room and redistribute more weight to the rear.

As far as your driveshaft issues, I'd recommend using that carbon fiber shaft if you have one and can make it work. Less harmonic issue potential, and it's yet another way to lose weight! If I recall, my stock shaft was somewhere between 29 and 30 lbs (~13.5 kg), the carbon fiber one I have weighs 11.2 lbs (just over 5kg), it's almost spooky to hold in your hands...
 

josbeat

Supramania Contributor
Jul 31, 2010
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What are your tire sizes to determine wheel diameter?
Also what vehicle speed do you typically notice the vibration?
This could help pinpoint where its coming from.

Easier to back calculate driveshaft RPM from wheel diameter and final drive ratio.

Carbon fiber will pretty much negate any issues with critical speed for your length driveshaft.

rear tyres are 315/30 18" 25,6" diameter from Bfgoodrich web catalog.
6th have 0.762 overdrive ratio and the diff is 5.29:1.

the speed when it starts is arround 200 kmh.
 
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Piratetip

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So with those specs your driveshaft speed would be 8,733 RPM @ 200km/h or 125mph.

Critical speed calculations don't match up with that but don't know the full specs on the driveshaft yet.

Calculated:
13,923 RPM Critical Speed
6,961 RPM 1/2 Critical Speed

Using:
40" length
.125 wall thickness
3.5" Dia
Alu - 6061 w/ density of 0.098
 

josbeat

Supramania Contributor
Jul 31, 2010
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spain
So with those specs your driveshaft speed would be 8,733 RPM @ 200km/h or 125mph.

Critical speed calculations don't match up with that but don't know the full specs on the driveshaft yet.

Calculated:
13,923 RPM Critical Speed
6,961 RPM 1/2 Critical Speed

Using:
40" length
.125 wall thickness
3.5" Dia
Alu - 6061 w/ density of 0.098


Thanks!
maybe is the rear diff , it have all bearings new and new crown and pinnion but that is not a easy job so i will double check that all is ok with it.
 

josbeat

Supramania Contributor
Jul 31, 2010
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it was a cold and wet day but the car was good
 

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josbeat

Supramania Contributor
Jul 31, 2010
483
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spain
the Albun in Photobuckett are deleted sorry
and in my computer i lost many photos aswell but i can try to make a new one. give me time.
 

josbeat

Supramania Contributor
Jul 31, 2010
483
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the lattest news are ...( i cant stop! )

i just bught a new front suspension kit, it is made for Drifft but i think i can use it for closed circuits aswell .
i am looking to wide the front track with long suspension braces and at the back with a deep dish wheels.
we will see the results soon.
the most difficult will be to cover the wheels with a nice set of weel archs , i bought a set of and i will see how it will look but if some one have an idea or design of a wide race supra , please let me look at it .
i like to see a supra with the look of the new Lexus race car.
 

josbeat

Supramania Contributor
Jul 31, 2010
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the car weight at the end , 1190 kg with fuel and 1260 kg with me inside jajaja!. i can adjust the weight balance from 52 to 50 but not less than 50% at the front.
next project is to remove the front of the engine bay and build a tubular one.
how many Lbs do you think i can remove from there??