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Discussion Starter #1
It's been a while since I posted on this. Last year was not good in various ways so the Pb still stood at 12.3/111 with a 1.8 60ft. In hindsight the car was settling onto the slicks as the springs had sagged and I was trying softer damper settings. Anyway after years of playing with Caltracs and/or A frames to improve traction I bit the bullet and decided to fit a 4 bar rearend. The limitations were not wanting to cut the bodywork because of the 8 point rule (this car is still street legal), working in a single garage stuffed with tools, and my welding,which would make a pigeon blush. So I made up some models in foamex and then had steel plates laser cut to suit. I tacked these together and trial fitted them.

The coilovers came from Gaz, who were very helpful. They are the 2" dia ones with 10-14.5" travel and 200 lb/in springs.I kept the existing panhard rod but with new rod ends and new axle mounting.The bars were made from 1" ID tube, with 5/8" UNF rod eyes in RH and LH threads and are 16.5" between centres. I used the existing spring mounts on both the axle and body but added additional fixings in the body for the front mount.



After more trial fitting the mounts were sprayed in hammerite and the bars powder coated.



The upper end of the coilovers were secured through re-enforced plates bolted through the rear wheelarch and then further stiffened by a thickwall square section tube across the car,tied to the base of the roll hoop.

So far testing has been limited to local roads (I was sitting on a box since I'm also making a new driver's seat) but the stance seems about right and the wheel/body clearance is increased.

Can't wait to get out and test this properly once the other Winter jobs are done.
 

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12.3 is already very impressive, looks like the 60ft will be a lot better now so 11s this year could be on ? Good luck with it. Rich
 

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Nice one Steve! I'm sure the 4 bar will make a big improvement.
One of the differences with the earlier Mk1/2 Spridgets (with the quarter elliptic springs and upper reaction link) is that they provided very nearly a four bar link rear end as standard..........But then they went to the full length rear leaf springs which wind up and hop!
 

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Discussion Starter #5
Thanks for the kind words. Phil I think the quarter elliptic setup only came off the front spring hanger mount, although it is almost a 4 bar. I wanted to give this a bit more strength given the forces involved off the line.:whistle:
 

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Looks like a really nice job Steve. A 12.3 with a 1.8 60ft is very impressive and id have thought a 4 link will help no end. with a 1.6 60ft i think youd be looking at a 11 second ticket :tup:
 

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looking forward to seeing this at shakey in March !

most of us can only dream about a 12.3 .............
 

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Discussion Starter #10 (Edited)
Thanks for the comments.
Joe,the problem with the 60ft is the turbo. Need to feed the clutch off the line to get it to spool,so slow first few feet,then it lights up with wheelspin until I shift. I've fitted up a line lock in the clutch line so I can get instant consistent starts,and will replace the lightweight flywheel with a standard one (2xweight) to stop the engine bogging.
Solly I won't make it to Shakey until May,probably Gary's Picnic,as I don't like getting salt on it and it is road driven to and from the strip. Also still have quite a bit to do on it. I will be out on my ' private' test track however!
Marcus I,m now in the middle of making a new seat in sheet Ali, will post on this later. Also quick engine out before the season.
Legend,thanks for the compliment, but the credit should go to the welder who laid such lines through my awful tacks. I have tried to design for strength rather than lightness so lots of stiffening ribs and all the bolts in double shear. Also extra support for the front mount as the stresses on the original fixing points would be excessive.
 

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Discussion Starter #11
Bit of an update. I've always fancied trying to make a seat, but I'm fond of the covers that have been on the car for the last 15 years. Anyway I've fitted a new 5 point harness and needed to fix the 5th point through the seat base,so decided to bite the bullet.This is the original seat

I bought a sheet of 1.5mm ali and some pop rivets plus a couple of hole punches off the bay. I used a scrap bit of square tube as a former for bending and did most of the cutting with tinsnips.

I had the original seat covers turned into loose cushions by the trimmer who made the originals,and used them to dimension the seat the seat.This was the result.

Needed quite a bit of tweaking to get the strength in it. I fixed it to the floor with bolts welded to strips of steel glued to the seat base. The seat cushions are a tight fit so didn't need retaining in place.

Fitted in the car with the new harness and some judicious blocks behind it for extra stiffness. The new harness works well,you really feel part of the car with it tightened up.
 

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Discussion Starter #13
Took the car to Shakey on Sunday for a few runs. Finished with a 12.5/108 and 1.8 60ft. Rodders excuses 1 and 2 the track was slippery and there was a headwind :shake:
Dave derry took some pics which showed the car settling back a lot on launch,and I might even have popped a front wheel.So I guess I need to raise the instant centre by playing with the location of the bars? Still groping around in the dark on setup of this lot.
 

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Wheel popping is good!
It shows that all the weight has transferred to the back wheels and so maximizes traction! Well done for getting out on the strip nice and early in the year.:rule:
 

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Discussion Starter #15
Thanks Phil. I might try moving the upper bars nearer to the axle centreline. Will move the IC rearwards and hopefully maintain the hit for longer? Anyway roll on Gary's Picnic.
 

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Discussion Starter #17
Thanks Robert, I now have a bewildering number of variables to play with - should be fun:pmsl:
 

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Discussion Starter #18
Well ran on Monday at Shakey with more ride height and stiffer damper settings. Managed a new PB of 12.2/111 so pleased with that. Some time lapse photos show the car really moving (rolling) side to side as I shifted,which suggests the spring rates are too low. Still some witness marks of tyre rub under the O/S arch. Launch was better with 1.76 60ft.:D
 
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