My Type 54 to sort of 47 Conversion

[RoddyMac]

Its been a while, the project/build is slowly progressing.  After tacking the rear uprights together and making a dummy hub bearing I found that the Girling calipers that I had earmarked for the project wouldn't work.  They cleared the hub and upright, but fouled the hub portion of the wheels I'm using.  So, after a small amount of Cardboard Aided Design (CAD) I've come up with some weld on adapters to take Miata rear calipers.  They clear the wheel and hub, plus have the added bonus of having a handbrake.  Now I just have to find someone to weld them up for me. 

I've also made two sets of reversed lower wishbones for the car.  The first set was slightly modified by hand which turned out to be a mistake, I messed up on one measurement which forced the fabrication of the second set.  I've also made the four trailing links, four clevises for said trailing links and two single upper links.  The next step is building a jig to set the suspension pick up points, and tack weld the points to the chassis.  I'm very curious to see how the suspension "moves" in bump and droop.  If I still had a license for solidworks I would have modeled it before fabrication.

Anyways, here are a few pics, and yes I really do need to clean the shelves in the garage.







And if anyone is interested, here's the drawing for the front and rear suspension, but the lower front wishbones don't quite work as pictured.





Rod

[BDA]

It looks like things are moving in a good direction! The uprights look really nice! Hopefully it won't be too long before you can put it all together for a final fitting. Keep up the good work! 

[Chuck Nukem]

Wonderful!! Keep it up!!

[RoddyMac]

Over the past couple of weeks I've managed to get the rear suspension to a point where I could bolt it to the chassis.  There have been a few small issues, but nothing major.  I'm now waiting on some more laser cut pieces for the rear uprights, once I get them I can finish weld the uprights and call the suspension "done".  Then its on to sorting out engine and gearbox mounts, followed by fitting the chassis to the body.

Here are some pics from yesterday:








Rod

[BDA]

It looks like it's coming along nicely!  The geometry in the rear is interesting. My memory from when I was racing (back when we chiseled wheels out of stone) was that the trailing arms were always equal length. It looks like you'd get some caster change (and maybe a little toe change as well?) - I'm not sure what caster (or its changing) does in the rear  . I remember we discussed rear caster (IIRC, there was a rear caste spec for some cars) and none of us had any idea what difference it made so we just worried at camber and toe.

Keep those pictures coming. It looks like it will really nice when it's done!

[RoddyMac]

From what I've read, caster isn't really important in the rear, but toe changes are.  The way its set up at the moment it toes-in under droop and under bump, so in theory if I set the toe-in to anything greater than 0, I should be okay.  Toe-out is to be avoided at all cost.   As for the unequal trailing arm lengths, the 47 is nearly identical to what I've designed and built, see photo attached of a car being put together at Banks (I think). 

This is my first IRS build, so I'm learning as I go.  I have noticed that Lotus used a larger diameter tube for the trailing arms, so the ones I've built will most likely get changed before the car is on the road.  I've been bugging one of the EITs at work about putting my design in a stress analysis program, but we're a bit busy at the moment.

Rod

[BDA]

Toe in under droop and bump is good! And being close to the original 47 rear suspension, you should be good. I didn't notice it before but it looks like the forward mount points of the trailing are not in the same vertical plane... Something else interesting about it!

I was about to say that the trailing arms would pretty much just be under tension, but in braking, they would take compression, wouldn't they? In that case, a little bigger section would be helpful.

[Chuck Nukem]

Incredible!! Out of curiosity what does your tube fame weigh with out any suspension on it? I am thinking about doing something like that on my 46. Has anyone sent you the dimensions of the dash board panels yet? I have been meaning to dig through my pile of tubs to make a template for you.

[RoddyMac]

To be honest, I haven't put it on the scales yet.  If I get a chance this weekend I will, but I can tell you its light enough for one person to pick up. 

Serge did measure his panels and posted the dimensions, but a template would be great to have as well.  I've changed the dimensions on my CAD drawing to reflect what Serge sent and I'm tempted to send the drawing off for a quote on laser cutting.  But, building the dash is still months away (though it would be cool to have the instrument panels all ready to go and on display at home).  I'm hoping to start on the bodywork and dash build once I'm back from my vacation in May. 

Rod

[RoddyMac]

This past weekend had the project go from non roller, to roller, to fitting the body.  It was so far the easiest work on the project, everything seemed to fit together without any major issues.  I had to do some minor trimming of fibreglass, and it looks like I'll have to trim the inner lip of the wheel arches, but nothing too major went wrong.







Rod

[BDA]

Man, that's got to feel good! It looks like things are moving along pretty smoothly. Keep up the great work!
 

[EuropaTC]

That chassis really is a work of art. I think you ought to have translucent or perspex bodywork inside the car so you can see it !

Ok, ok, maybe that is going too far but the frame looks great.

Brian

[Chuck Nukem]

As a man who has recently experienced hundreds of hours of bodywork fixing stress cracks and accident damage in a twin cam body...I wish you luck!

[460384]

Rod,

What a great job on your chassis.  Will you make one for my S1b?

Tom/Colorado 

[RoddyMac]

Tom,
Unfortunately building a second chassis is out of the question at the moment.  I'm having a hard time to find time to work on the current one.   

Rod