1969 Triumph Spitfire Mk3: Long term re-build 4AGE

[krissto]

Awesome!

[Darkspeed]

A bit more progress on the bones - now reached the stage that is a little more tricky as shaping the tube joins is complicated by all the angles. The cross tube is quite an involved one as it joins at a bend. All those joints need to be right before the final assembly and tacking together.





















Should be completed - tacking up wise - this weekend - But final welding up will have to wait until I pick up a new bottle 0f gas.

[Darkspeed]

Just before a thunder storm and torrential rain stopped play I completed the the tube end profiles on the bracing tube.

[horrido]

Does the arch shape of the original bones have some purpose?

[Darkspeed]

Tacked - I am more than a little biased but I think that looks right.

[Darkspeed]

Jul 4, 2021 16:21:32 GMT horrido said:

Does the arch shape of the original bones have some purpose?

Yes - to provide clearance for the original Rotoflex coupling - used on the GT6 MK2





krissto will no doubt elaborate on the driveshaft changes that means the curve is superfluous.

[horrido]

Ah i see. Thanks.

[krissto]

Jul 4, 2021 17:07:45 GMT Darkspeed said:

krissto will no doubt elaborate on the driveshaft changes that means the curve is superfluous.

He will indeed.  The banana curve is no longer needed because I am using CV driveshafts, as provided by Canley Classics.  No rubber donut to clear, so the wishbones can be straight (and give a little more ground clearance).  Canley no longer supply these CV driveshafts, but a similar product is available at Rimmer Brothers.  See rimmerbros.com/Item--i-RG1314

[krissto]

I really like the look of the progress with these.  Some more metallic blue paint is on its way to me to give the wishbones that finishing touch...

[vitesseefi]

Nice wishbones. Proper job.

Just a thought/caution on the adjustability. I don’t think it will be an issue with the Canley shafts as the inner CV has a fair bit of plunge, but on the Rimmers/Jigsaw/CDD ones with a lobro inner joint, as well as the Rover 100/Volvo 340 versions I used to do, there is very little spare plunge in the joint. Something like 18mm available vs. 11mm required. Therefore winding out the adjustment to give more negative camber needs to be done with a bit of caution so you don’t run out of travel.

Nick

[biturbo228]

If you do run out of plunge then I do happen to have a set of canleys driveshafts that are surplus to requirements now I've plumped for an R160. Just ping me a PM, they're not going anywhere.

Wishbones look great

[Darkspeed]

Jul 5, 2021 13:02:54 GMT vitesseefi said:

Nice wishbones. Proper job.

Just a thought/caution on the adjustability. I don’t think it will be an issue with the Canley shafts as the inner CV has a fair bit of plunge, but on the Rimmers/Jigsaw/CDD ones with a lobro inner joint, as well as the Rover 100/Volvo 340 versions I used to do, there is very little spare plunge in the joint. Something like 18mm available vs. 11mm required. Therefore winding out the adjustment to give more negative camber needs to be done with a bit of caution so you don’t run out of travel.

Nick

Cheers

The wishbones can only be adjusted to reduce the amount of negative camber. They are the same length as standard when fully extended.

I think krissto said that at the chosen ride height the car would have 5 degrees negative static and he wanted the option of being able to pull that back a few degrees - I think originally it was asked to give adjustment to pull back all 5 degrees but I said no as I had a minimum of thread engagement on the bush end into the wishbone that I would be happy with so I think the limit is 4 degrees.

I am not sure he would ask me to do them again as it has taken 6 months for me to get this far.


New bottles of gas collected this morning for both the MIG and the TIG so no excuses now for not having these finished for next weekend.

[Darkspeed]

Jul 5, 2021 14:01:53 GMT biturbo228 said:

If you do run out of plunge then I do happen to have a set of canleys driveshafts that are surplus to requirements now I've plumped for an R160. Just ping me a PM, they're not going anywhere.

Wishbones look great

Cheers - hopefully the old saying what looks right..... should hold true.


CC items are what krissto has

[vitesseefi]

5 degrees negative….. going low then! Didn’t think you could get to 5 deg on the roto set up but maybe he’s working outside the usual travel limits?

Plunge limitations could apply in either direction so care still needed.

Nick

[krissto]

I will try to explain in as few words as possible. My car has a de-cambered (i.e. flatter) GT6 Mk2 rear spring.  I did not wish to use a lowering block and the car sat far too high with a stock GT6 spring.  This is mainly due to my Spitfire being significantly lighter at the rear.   With the de-cambered spring and the standard lower wishbone, there is too much static negative camber and the rear height is about right, not really any lower than standard.  If I use the Eickhof 44mm lower wishbone mount, this is made even worse - about 5 degrees of negative camber!   So we have designed the tubular wishbones such that the length can be reduced, not lengthened and this should pull the vertical link more upright using the Eikhof location.  I now have a means of adjustment, whichever mounting hole I use.

[biturbo228]

Neat. Who decambered your rear spring? I was looking for a similar solution for my GT6 one as it's way too stiff so rides really high at the back. I've got a Spitfire one to test as well, but we'll see. Was also looking at the fibreglass ones you can get from a company in the States whose name I can't remember.

Have you done any modelling with your new suspension setup? I've done a bit of playing around with the Racing Aspirations calculator and a host of different GT6 rear suspension options. Some interesting things happen with decambered rear springs vs lowering blocks. Camber curves are broadly similar, but the roll centres are lower with a decambered spring (generally a good thing, especially a good thing GT6 rear suspensions with their very high roll centres).

How far have you lowered it, and do you know the nominal length of the new wishbones? Will see if I can knock up a model if you're interested.

Oh, and you're right to avoid lowering blocks and relocation brackets. The larger lowering blocks (-3/4", -1") with holes that drop the lower wishbone start exhibiting some weird effects. -1" with the racing bracket gives a flat -3deg of camber all through the range which is very interesting (no idea how it would drive). Similar thing happens with the 25mm drop brackets and 3/4" lowering blocks, but with a flat -2.5deg camber. 25mm drop brackets and 1" lowering blocks have a weird compound camber curve that means you lose camber in both bump and droop.

Found this out with my patented GT6-suspension-o-matic, and later confirmed with the more precise (but less accurate, on account of the leaf spring changing length as it compresses) digital models.

[krissto]

I commissioned Owen Springs to make me a flatter spring to GT6 Mk2 spec (same rate, leaf lengths, thickness etc.) but de-arched by 2".  That is, 2" less height from the ground to the centre of the bottom leaf.  They were also tasked with fitting thin delrin thrust buttons between the leaves, rather than perishable rubber items.  The new tubular wishbones that Darkspeed is making are the same length as standard (nominal) but can be reduced in length by up to approx 16mm.  Finally, the Eikhoff inner wishbone pivot is 44mm lower than standard.  I'd be interested in what your model predicts...  

[biturbo228]

Thanks man will see what I can produce!

[vitesseefi]

Jul 5, 2021 17:50:41 GMT krissto said:

I commissioned Owen Springs to make me a flatter spring to GT6 Mk2 spec (same rate, leaf lengths, thickness etc.) but de-arched by 2".  That is, 2" less height from the ground to the centre of the bottom leaf.  They were also tasked with fitting thin delrin thrust buttons between the leaves, rather than perishable rubber items.  The new tubular wishbones that Darkspeed is making are the same length as standard (nominal) but can be reduced in length by up to approx 16mm.  Finally, the Eikhoff inner wishbone pivot is 44mm lower than standard.  I'd be interested in what your model predicts...  

Interesting. But how does the eye to eye length of the spring compare with the original if it were compressed to the same ride height? Can't help thinking it's a bit shorter as I'm almost certain that the most negative I've ever measured on my Vitesse is 3.5º at full bump.

Anyhow, if it gives what you want, fine, but as you are in effect narrowing the track, do check that that the driveshafts can manage the full range of movement - over compression is particularly destructive...... AS I said before, you may well be OK with CC shafts but I'd be very concerned about the others.

Nick

[Darkspeed]

All gassed up I figures I would do the welding





























Happy enough with the way it went until I checked the alignment after the final welding of the cross brace which has to be done out of the jig - and it had pulled the bush out of alignment - .

A painful mistake - I tried another method on the second one and it reduced the stress misalignment but even applying a bit of heat it would not correct in the right planes. I now know the sequence I should have used and how I should have welded them in the jig but to sort these out now I will need to make two new bushes cut the others off and weld in new ones.


Basically the 1" onto 1" at the angle on the bend is a long weld - and its too much - either only lightly tack in a couple of places the bush on that leg and weld the bush on last of all or only use a brace tube of 1/2 the diameter.


ing annoying but I will take the positive from this that I have had some much needed practice.

Probably could sort it as is if I had an oxy set but that's at my mates where the G27 is so quicker for me to cut off and reweld.