Matt's 1970 'Trans-Am' Cuda

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ScottyDave
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Re: Matt's 1970 'Trans-Am' Cuda

Post by ScottyDave »

Nice fab work :thumbright:
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Re: Matt's 1970 'Trans-Am' Cuda

Post by Matt74 »

Great stuff!
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Re: Matt's 1970 'Trans-Am' Cuda

Post by Cannonball »

How did it feel Matt ???? smashing work and I bet you enjoy it as its not now building a car its improvement time
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Matt
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Re: Matt's 1970 'Trans-Am' Cuda

Post by Matt »

hi Dunc,

I thought the car was going to feel more stable mid-corner, but it's much the same. Turn-in appears to be sharper/quicker though for some reason.

Once I switch to stickier tyres I expect the panhard rod will make a bigger difference though.

Many more 'improvements' required now the car is being driven a bit harder. At the top of the list :

1) Possible oil being sucked into PCV valve. Massive smokescreen out the rear after long straight/right hander

2) Fuel leaking from tank breather

3) The groaning noise from the rear in hard corners appears to be the prop still rubbing the floor. I wrapped the rear of the prop in gaffa tape and there's now a section of it smeared over the tunnel.
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Re: Matt's 1970 'Trans-Am' Cuda

Post by andyrob »

Matt wrote: Sun Feb 09, 20 4:25 pm hi Dunc,

I thought the car was going to feel more stable mid-corner, but it's much the same. Turn-in appears to be sharper/quicker though for some reason.
That is because you have changed the roll centre of the rear of the car, raising the rear roll centre gives you better turn in, lowering it gives you better traction off the corner
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Re: Matt's 1970 'Trans-Am' Cuda

Post by MattH »

Matt, you are starting to get me interested in this racing lark. Maybe a couple of hillclimbs to start with, Prescott etc.
It just crossed my mind what an Aussie Charger would be like, Bathurst replica and all that. :-k :-k

Oh but i have no time and too many projects already! Maybe a retirement idea to ponder on?
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Matt
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Re: Matt's 1970 'Trans-Am' Cuda

Post by Matt »

Hi Andy,

Yes I've just figured that out ! Roll centre probably only higher by 2 or 3 inches but it looks like the difference can be felt even by an amateur like me.

Remains to be seen whether the higher roll centre is a net benefit or not ...

Less body roll (probably good) , but as you say, less weight planted on the outer rear tyre.

Whilst building the car I never thought it would tend towards oversteer, but it's starting to feel like it's heading in that direction. .
Last edited by Matt on Sun Feb 09, 20 8:58 pm, edited 2 times in total.
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Matt
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Re: Matt's 1970 'Trans-Am' Cuda

Post by Matt »

Hi Matt,

an Aussie Charger would be superb. Very cool - and potentially light and fast.

I've got way too many projects , although this one is really taking over now and getting all the attention.
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Re: Matt's 1970 'Trans-Am' Cuda

Post by andyrob »

Hi Matt, 2-3 inchs is hugh amount in altering the roll centre, thats why I was suggesting a watts linkage, as on my cars the centre of the watts linkage can quickly be wound up or down during a practisce session to chance the balance between turn in and drive off the corner, I do fiddle with this from track to track, but normally by less than an inch and i can feel the difference with this amount
There is alot to learnt with chassic dynamics, getting somebody really knowlegable to look at your car or watch your car at a race meeting will help you so much
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Matt
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Re: Matt's 1970 'Trans-Am' Cuda

Post by Matt »

Thanks Andy that's good advice.

Looking at the Roll Centre again, and taking some more accurate measurements, it would appear not to have moved much at all .

Maybe the new lack of sideways compliance is making the turn-in feel different, or maybe I'm just imagining it !

In the future I may have to re-think the axle bracket, and also extend the chassis bracket downwards, to allow some more adjustablility.
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Re: Matt's 1970 'Trans-Am' Cuda

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Last edited by Mark B on Sun Feb 23, 20 7:58 pm, edited 1 time in total.
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Re: Matt's 1970 'Trans-Am' Cuda

Post by MattH »

Superb, these models are stunning, I have the Sam Posey car
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Re: Matt's 1970 'Trans-Am' Cuda

Post by Matt »

Couple more little jobs:

Installed a fuel pressure gauge on the dash to help diagnose a stalling problem. Engine will tick over all day, and has no running issues otherwise, but will stall if you dip the clutch after a run and try to coast.

Sender unit plumbed into fuel line
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And gauge inside
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Fitted a March underdrive crank pulley , and shorter V-belt
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Calibrated the speedo, finally. Ever since the car was finished, the speedo has pegged at 150 pretty much as soon as you start rolling.

One calibration method is to drive a measured mile, pressing the speedo function button at start and finish. Couldn't figure out a practical way to do this, so bought a digital counter with magnetic sensor (£6.95 on ebay..) ,and strapped a magnet to the tyre. Ran the car on axle stands . One mile = 746 revolutions of this tyre size.
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Fitting Moser green bearings

Grinding off the old ones very carefully . If you can get the metal thin enough they'll split on their own.
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Pressing on the new ones
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Ready to refit
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I quite like the oil sealing with these - no more sealant required on the retainer plates during assembly, and much less fuss when removing halfshafts.

Although, surprisingly, there is still end float built into the bearing assemblies - about 8 thou. Was hoping that wouldn't be the case.

Upon installation, track width has been increased by about 3mm - confirmation that the half shafts are no longer butting together in the middle, and all is OK.
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Re: Matt's 1970 'Trans-Am' Cuda

Post by DaveB »

I didnt think the green bearings were suitable for hard cornering Matt.
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Re: Matt's 1970 'Trans-Am' Cuda

Post by SAV@RPM »

Hi Dave
Lots of stuff on the Internet over the years concerning the Green bearings and there suitability for circuit use. I used them on the Superbee running sticky 275 Hoosiers on the rear and in 3 years of circuit racing I never had an issue. Had plenty of problems running the original bearings with oil leaking past the seals though. I think there may have been some issues with the very early green bearings but the later style are fine, fitted quite a few in road cars over the years and have yet to replace any. I can only speak from my experience though.
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