Cobra 427 Build

[CL290005]

looking good, this might be ready for the kit car show

[Alan Cutler (Adge) - Dorset AO]

Great work Gary, be good to see a rolling chassis. A good milestone methinks.

Keep up the good work.

[KugaWestie]

[KugaWestie]

A bit of work on the brake pipes this evening at the front end

 

 

Nearly done at the front. I need to weld a couple of brackets on and then measure up and order some flexible hoses.

[KugaWestie]

I have been working on the steering over the last few days.

I was not happy with the difference in angle between the steering rack and the lower wishbone with the Jag track rod ends fitting into the steering arm from the bottom. 

So i contacted @Ben (bunje) and asked him to open out the tapered hole in the steering arm, then fit a tapered top hat bush into the steering arm to reverse the track rod end to fit from the top instead. This will et the steering rack much more parallel to the lower wishbone (by approx 80mm) which should hopefully eradicate any bump steer.

 

[KugaWestie]

@Ben (bunje) did a great job, which meant today I could have a look at positioning the steering rack.

So I assembled the rack with the thread adaptors

 

[KugaWestie]

I tack welded an angle iron in place across the chassis to house the rack

 

 

 

[KugaWestie]

And then fitted the rack, again everything is loose at present

 

 

Here you can see the angles of the lower wishbone and the rack. If it had been fitted as standard the trackrod end would have gone into the arm from below, which would have massively increased the andgle of the steering rack from the gaiter.

[corsechris]

Hi Gary,  I hate to be “that guy” again, but to be fair, I do seem to have a gift for it .......but did you measure the bumpsteer before making the changes (or was it a well known issue with that chassis)?  Having had a kit with shocking bump steer designed in by the manufacturer, I certainly wouldn’t be surprised if this was a known issue though.

Your solution looks great, but looking right and being right doesn’t always follow with steering/ suspension geometry, you really do have to calculate it then just meausure it once you have it built. Tiny changes can have a big impact, so if you can, it’s a good idea to allow for some adjustment in the vertical location of the rack and track rod ends.

As always, forgive me sticking my oar in if you have all this in hand 

[BenD]

all looks good as usual Gary. keep up the good work

[KugaWestie]

2 hours ago, corsechris said:

Hi Gary,  I hate to be “that guy” again, but to be fair, I do seem to have a gift for it .......but did you measure the bumpsteer before making the changes (or was it a well known issue with that chassis)?  Having had a kit with shocking bump steer designed in by the manufacturer, I certainly wouldn’t be surprised if this was a known issue though.

Your solution looks great, but looking right and being right doesn’t always follow with steering/ suspension geometry, you really do have to calculate it then just meausure it once you have it built. Tiny changes can have a big impact, so if you can, it’s a good idea to allow for some adjustment in the vertical location of the rack and track rod ends.

As always, forgive me sticking my oar in if you have all this in hand 

Hi Chris,

No problem with you being "that guy" 

The difficulty I have is that I have not been able to establish what rack was used originally, and also how it was positioned, so it really is a start from scratch effort and see what happens if that makes sense!

[corsechris]

Sorry Gary, I really should have known you'd have had a good reason 

Reminds me I need to make a new bump-board   Mind you, I saw a good technique recently that uses a laser pointer fixed to a wall, a large mirror attached to the hub and a piece of graph paper suitably located and fixed to the same wall as the laser pointer. Looked very effective.

[KugaWestie]

15 hours ago, corsechris said:

Sorry Gary, I really should have known you'd have had a good reason 

Reminds me I need to make a new bump-board   Mind you, I saw a good technique recently that uses a laser pointer fixed to a wall, a large mirror attached to the hub and a piece of graph paper suitably located and fixed to the same wall as the laser pointer. Looked very effective.

Chris, the whole reason for doing threads like this is other people sometimes see things that have not have been considered/could be done better etc, so keep on chipping in please 

I am interested in the bump board you mention though, as I have no idea how to check what I have done whilst in the workshop

[Kingster]

9 minutes ago, KugaWestie said:

the whole reason for doing threads like this I see other people sometimes see things that Ishtar not have been considered/could be done better etc, 

Absolutely! Saved my bacon once or twice during the build

Although what a Mesopotamian deity has to do with building cars I don’t know 

[corsechris]

Found this site, describes the laser method petty well.  https://www.svtperformance.com/threads/a-r-t-laser-bumpsteer-gauge-for-rent.468364/

A bump board is ever so easy to DIY though, loads of info out there, but briefly, you need a frame or board that sits on the floor, hinged to that is another frame or board that sits more or less vertically. You align the hinge axis along the length of the car. You also need a board or sheet of some non flexible material that bolts to the hub. Mark this with a series of horizontal lines, spaced as far apart as you feel neccesarily, but start at say 1cm. Attach a fixed pointer/rod/whatever to one vertical edge of the vertical board, this rests on the bit you bolted to the hub, at the other end of the hinged board, you put a DTI. 

Set the suspension at ride height, set the hub so the lines are horizontal, lock the hub, tweak the position of the whole bump board so your pointer hits one of the lines, zero your DTI about mid-range of it’s travel, then move the suspension up and down in increments, measuring the movement on the DTI. Plot this against vertical deflection from ride height.

 

As always, I make a simple process sound horribly complicated.....I have no doubt you’ll find much better descriptions out there