GT-Forte GTs40 build

[David]

Stuck the engine back in and changed my mind on the frame side of the mounting backets.

Basically it er doesn't fit in with them in place! =8-o
Unless that is I remove the sump (both parts which I think would involve removing the gearbox) every time I want to take it in or out. I don't really fancy that.

Not to fear, I have a plan, bolt in plates it is. Back to the angle grinder and welder!

 

[David]

 

[David]

 

[Paulbav]

Jeez, looking at that it really makes me feel a bit rubbish when I think how I struggle with a bit of aluminium paneling on mine.... Truly top work keep it up:thumbsup:

 

[David]

Cheers.

Well its my own fault for deciding I wanted a different engine and picking one with DOHC. Plus I've modelled the major changes and there is an improvement in stiffness. Especially as I've halved the big hole in the chassis for the engine as the sump on the 1UZ-FE I have is forwards. I'm setting the engine up so the bottom of the sump is level with the bottom of the chassis, you can see here how much of a big gap there is here.

Still got a bit more triangulation to put in. I had hoped to re-use the existing diagonals but they didn't properly line up any more. You can kind of see in this picture, about 1/3 didn't sit 'under' the new chassis members.

Truly terrifying taking an angle grinder to the chassis though.

 

[David]

 

[David]

Just for interest, the modelled tests of my modifications. For an estimated 7Kg weight increase have made the rear ~50% stiffer. They're not totally accurate and only part models.

For information the deformation is 25x on all of them (otherwise you wouldn't see it!)

Twist - Before

Twist - After

Bent up - Before

Bent up - After

Bent sideways - Before

Bent sideways - After

I didn't really start modifying for reasons of increasing stiffness though, I just wanted more clearance for the downpipes, modelled it to check I wasn't making it worse and got a bit carried away!

 

[Michel]

Nice study but your modeling is done with round drawing and your mod tube is square and rectangular ? ( I°/V ) are different or am missing something ?
Otherwise your modification seems to be more than correct and perfectly done so I will not be worried at all with the good result .

 

[David]

That's just the way the modeller solves it, it has a number of different ways of mesh types and for chassis design the 'beam' mesh model is used. The model itself is done with the 'right' size and thickness of tube so they're reflected in the model even if they're not shown. It's not totally accurate as it's only from the rear bulkhead back to the horseshoe and doesn't take the roll cage into account but its enough to tell what (general) effect the changes should have.

 

[Darrin]

I'd be curious to know how paneling affects this if that could be done.

 

[David]

Panelling will make things much stiffer, the floor for example is a critical component of this type of design chassis.

You can strategically change the thickness of the panelling depending on how much you want to stiffen up sections, for example one of the main things I noticed when modelling it was the amount that the 'square' through which the lower radius arm passes deflects

You can't brace that as well basically the radius arm needs to pass straight through the middle, I had the intention of putting a fairly thick piece of aluminium (2-2.5mm) over there and seriously riveting it in place (2-2.5cm spacing, double row) with the smallest hole possible for the arm to pass through.

I could model with panelling but it would take easily 20x the time if not more to create the model.

 

[David]

Bit more work, very very nearly finished this side now.

Also started on a few other bits

 

[David]

After a bit (well a lot) of consideration decided to bin the Granada front uprights and use a pair of TVR Tuscan S ones with 322mm disks and AP Racing CP6600 calipers. Does mean more modifying though... Although I get to make up my own geometry (ie lose the ridiculous scrub from the Granada uprights). Which is nice.

I have the suspension points and lower arm modelled, need to model the upright and upper arm then make a final call on the front tyre size. Then I can get the wheel offset and then SAI sorted for a (very very) tiny bit of scrub. Aiming for ~6deg caster angle (with the chassis horizontal, this will drop when nose down) and 7-8degree SAI (KPI).

 

[David]

More work, finished this bit of this side now

 

[David]

Back to fun with card again

 

[David]

Another piece

 

[David]

And we're done.

Well for that section anyway.

I'm not keen on the radius arm mounts hanging there in empty space just held by the bottom and welded to the side. Darren changed the design after my chassis and IMO the later design is much better. So as I don't want to go to all the effort of changing to the GTs40 mk2 spec a bit of reinforcement instead.

And then a bit of bracing.

More bracing to follow. May see if I can get a bonus garage day come the B/H.

 

[David]

Seeing as finally finished with it, threw some paint at the tail end of the chassis.

Needs some more coats and only painted up to the end of the sponsons so far.

 

[Paulbav]

Looking very good, do you ever wish you stuck with a SBF... :laugh:

 

[David]

Amazingly not, I want a quad cam!
Although I do wish I'd got the coyote version of the chassis and I should have got busy with the angle grinder and welder earlier. I wasted too much time making my life hard trying to not make any chassis modifications.

As it stands its easy to drop an SBF in, gearbox position doesn't change and I'll make up brackets to stick the original mounts back in so if I do change my mind some time down the line it'll just be bolt in job. Although might need to chop out the extra bar I put in the middle of the engine bay!