GT40 Aluminium Mononcoque Chassis

Here are some pics of an aluminium 16 swg rivited and bonded chassis Im building for my GT40

In these pics the chassis weighs 145 lb. The finished chassis will weigh less than 250 lb including all mounting points, and roll cage....

P1010709.JPGP1010717.JPGP1010723.JPG
P1010726.JPGP1010731.JPGP1010685.JPG
 

Doc Watson

Lifetime Supporter
Sweet! if I recall an interview I saw, Eric Brodey wanted the original to be aluminium but the money said go with steel.

How is the motor mounted and what about the roof and pillars? aluminium?
 
The motor will be mounted in a similar way to the Maclaren M8FF, M20.

The engine /gearbox, will be a semi stressed part of the chassis

.Im on a very limited budget, and im not a skilled sheet metal worker, so it will have a fibreglass spider......
 
I think the fabrication looks pretty good to me, are you working from any kind of diagrams ?
I feel you can always tell whether someone knows what there doing and taking care in there work when you look at things such as the spacings of the rivets and the quality of the folding and the way they look after there workshops.
It's having pride in what they do.

Interesting project , keep posting
 
These are the only drawings I have for the chassis. I only have a 4ft treadle guiloteen, and a 3 ft folder, so to make the longer pieces these plans were taken to a sheet metal shop, converted to CAD, lazer cut, and folded up on a brake press

CHASSISPLAN3.JPGCHASSISPLAN6.JPGSIDEPLAN2.JPG
SIDEPLAN22.jpgsideplan222.jpg

All the other pieces less than 3ft are designed in my head, I work out the bending allowances, draw it on the alloy sheet. cut it, and fold it up

How the chassis looks, is just as important to me as its stiffness and strength.
 

Jim Rosenthal

Supporter
Very nice. Some of the Safir Mark V cars had aluminum monocoques- maybe one or two, I think. Ought to be interesting from the weight standpoint, the car is going to be very light. How stiff do you think it will be- as stiff as a steel chassis?
 
Mick,
very, very impressive work and I hope you're going to keep us regulary updated with posts of your progress
Regards
Andy
 
Hi,

Thanks for the comments on my chassis. I started looking into building an alloy chassis about 2 yrs ago, and about a year ago, I decided to build one. I started building my chassis in March this year. Its taken about 200 hours workshop time to get the chassis to its present stage, but I have spent many more hours thinking about how im actually going to build it....

In the tunnel section alone, there is about 450 rivets, I geuss there will be about 3000 rivits in the chassis when its finished...

Jim,
The chassis stiffness, has been the hardest part to achieve, getting the strength isnt difficult, but the stiffness requires a lot more thought and design

For any given chassis design, the stiffness depends on 3 main things

1 ...The stiffness of the material you are useing. ie steel or aluminium

2 ...The amount of it you are useing ie. 0.8mm 1.5mm 2.4mm etc

3....How the material is joined ie ...Riveted... Bonded... Riveted and Bonded...Spot welded...Stitch welded...Fully seam welded

Compared to a GT40, I dont have a steel spider, so I will loose stiffness there, but because I will have a full Roll cage, that will give me that stiffness back

Although my chassis looks similar to a GT40 chassis there are major differences, the GT40 has one large side sponson with ribs. On my chassis, the side sponsons have ribs in them, but the sponson is effectivaly split into 4 different sections, giving it greater stiffness than just one large sponson. The triangulated section behind the seats is in 2 sections, amd also the cross member where the dash sits, is also built in 2 sections.

With all this taken into account, and other design features Im confident my chassis will be as stiff as a GT40 chassis....

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Tom,
The radius rods will attatched to the 50mm x 3mm Virtical box section at the back of the tub, this is where the engine gearbox mounts will attatch to the tub, The engine gearbox, will also be attatched to the back of the side sponsons,( I havnt made these mounts yet ) to spread the loads over a larger surface area. The Roll cage will also attatch to the upper part of the box extrusion, also the inner part of the box will have 1.5mm steel bonded to it, to give added stiffnes, and strength
I have removed the rear part of the triangulated cross member so you can see how it is constructed

P1010799.JPGP1010801.JPG
 
Tom,
The radius rods will attatched to the 50mm x 3mm Virtical box section at the back of the tub, this is where the engine gearbox mounts will attatch to the tub, The engine gearbox, will also be attatched to the back of the side sponsons,( I havnt made these mounts yet ) to spread the loads over a larger surface area. The Roll cage will also attatch to the upper part of the box extrusion, also the inner part of the box will have 1.5mm steel bonded to it, to give added stiffnes, and strength
I have removed the rear part of the triangulated cross member so you can see how it is constructed
Dear Mick thank for those pics. The attachment is clear, but this way at least the lower radius rod will run parallel to the chassis. On every car i´ve seen so far with this kind of rear suspension construction, the radius rods are running towards the outside of car and connecting there to the uprigt. This in combination with the lower and upper control arm forms a big triangle. I think if you run them parallel your toe change will be much bigger than in the versions pointing outwards. The farer outsid you connect to the lower and upper control arm the less your toe change will be.

TOM
 
Clayton,

I will be useing Avdel Avex 4.8mm Blind Rivets...This type of rivets are used on FAA Certified Aircraft.


Because Im useing mainly 50 mm lap joints. The bonding, will give the joint its stiffness and strength. The rivets are really only holding the sheets together as the adhesive goes off, but also they will ensure I have a thin even layer of adhesive, that will give the stiffest joint possible with the adhesive.

Mick
 
Hi Tom,

Thanks for the info...Originaly, I was going to have the mounts further towards the middle of the car, as you can see in this pic, but I changed it because it was far to strong and heavy....you could drive a tank over it, and it wouldnt brake.......

P1000370.JPG

Because I havnt riveted and bonded the chassis together yet, it will be easy enough to move the radius rod mounts further towards the middle of the car

What ctr. to ctr. distance would you recomend for the radius rod mounts, I have 10" rims with 295-50-15 tyres

Thank for the help

Mick
 
Hi Tom,

Thanks for the info...Originaly, I was going to have the mounts further towards the middle of the car, as you can see in this pic, but I changed it because it was far to strong and heavy....you could drive a tank over it, and it wouldnt brake.......

View attachment 56635

Because I havnt riveted and bonded the chassis together yet, it will be easy enough to move the radius rod mounts further towards the middle of the car

What ctr. to ctr. distance would you recomend for the radius rod mounts, I have 10" rims with 295-50-15 tyres

Thank for the help

Mick
MIck
Dont think i can tell you a number. It depends on what uprights you want to use, what your trackwidth will be. You would need to know where exactly your uprights are positioned, and where on your uprights the radius rods connect to. Than you need to check the clearance of radius rods towards your chassis, to define the need for evtl cutouts. I think you want to have the location of the front radius rods mounts as far towards the middle as possible ( still clearing the engine and headers) for best geometry.

TOM
 

Ian Anderson

Lifetime Supporter
Supporter
I have heard that the front mount should be in line with the rear mount.
That way you get the least geometry change during bump and droop.

Ian
 
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