B GT Suspension

As promised (quite awhile ago!) here are some pics of the coil over suspension for the BGT. We are working on fitting the rear suspension today, the front is all but complete.

A few more....

Right back to work re-fitting the gearbox and prop shaft!

Where did you get all that from?? Never seen anything like it. You running a 3 link rear, with leaf springs as well?

I recognize that blue and satin black. Beautiful stuff!

Looking good Tom.

Where does the top of the coilover unit on the rear suspension fix on the chassis?

The rear suspension design looks very similar to the Colin Chapman Lotus 7/Lotus Cortina design but with more bracing on the rear axle to prevent the diff casing from flexing under load.

Tom, I'd be interested to seeing the rear supsension photos when you get all the links hooked up. I worked on a couple of cars with the wishbones, both Spridgets, both use the original drain plug area of the rear housing for the rear attachment point of the wishbone, one of the Spridgets I worked on the person who did the fab work, made no alternate diff drain, so that was huge PITA, I see Dave had added a alternate diff drain plug (tu)

Hap, I learned the hard way that attaching the rear of the A-frame through the banjo drain plug will quickly lead to housing cracks. The way this is done is to bridge the side loads out to the tubes via the structure you see here.:)-D

Fascinating. What is the prevailing wisdom on wishbone, triangulated type rear suspension? I thought there were issues with this. However, looking at this it seems like a super simple good idea. Lightweight, simple with the benefit of having the roll center really low.

The suspension is like a 3-link minus a lateral control device. Instead the middle link serves as the lateral control. Articulation should be fine without bind. I would like to know where the upper links attach to the chassis.

Two final pics of the day,

I will post some pics of the upper links when they are finally attached, we need to set the axle in the car at its final height relative to the body prior to deciding exactly where the upper arm slots will go to ensure we have a reasonable amount of adjustment on the angle of the upper arms.

The body of the car is set on blocks in the final two pics at its approximate final ride height (dictated by the front suspension)

As for the rear coil overs they will be mounted as part of the rear roll cage within tower structures, these will allow vertical adjustment. pics to follow.

Tom

Paul and Bill, the lower A-frame has proven it's mettle in several other race cars that I've done. One key is that it is triangulated for stiffness and made with 1 1/4" OD, .125" wall tubes. The rear Heim joint is 3/4" shank, 5/8" eye attached to the axle in double shear.

Low roll center and simplicity are the big advantages. Upper links are angled(side view) to control roll steer.

Yeah - IIRC the weak point on the Lotus was the attachement at the diff. The pictures above show a damned skookum attachment point on the MGB, so it should hold up pretty well.

Skookum???:S

Maaybe I should go buy another shell, LS3 and join the thunder sports guys.

Awesome job Tom, hurry up Snetterton 26h feb has a few places left !!

Thanks everyone for the positive comments

Without the help an advice from so many people on this forum the car would be nothing like it is today so thanks again

Hi all

Just finished the work for the day on the race car.

The project for the day was rebuilding the rear axle prior to fitting it next weekend

The locked 4.3 diff has been fitted (we think this may well be our usual dry weather race diff for most circuits), axle shafts plus new seals fitted and the biggest job getting the rear disc brake set up to fit as it was originally designed to go on a banjo axle not the hybrid axle we are now using.

In the end it went together very easily the calliper brackets did not require any modification which was our biggest concern.

It also allowed us to find out what our base rear track width is, this turned out to be 52" from hub face to hub face

Part of the work earlier in the week involved fitting extended wheel studs so this will be adjustable with spacers

Looking forward to next weekend when the rear axle will be attached to the car and the upper shock mounts fabricated

Tom

Pics / info on rear disc brake setup please. I've got a Banjo axle in my GT race car, and am thinking about discs brakes. I can cobble something together, but if there is a kit or something that is easier / better I would go with that.

Hello, detail on the rear disc brake set up as requested, in principle we looked at the Scarebird conversion available from the US but decided that we could produce a simple conversion ourselves. The parts used are the rear brake callipers from a SAAB 9000, Rear discs from a Hyundia Sonnata and our own bracket which mounts the calliper to the axle casing bolt holes. You will note from the following pictures that our rear axle is a hybrid with banjo casing and tube axle ends built by Dave at FAB-TEK. We had the same set up on the standard banjo axle fitted previosly, so this conversion fits both set ups. The detail I will post on the next reply with measurements. Hope this gives you some ideas.

Pictures show the individual parts used, the red bracket is made on the principle "keep it simple but strong" the bracket is made from 7mm thick steel 10cm x 50cm, bolt fixings all match axle fixings and dimensions, This set up worked well on the banjo axle fitted before and never distorted so we do not expect any probs this time round.

Hi, I've put rear discs on my Salisbury axle using Rover 600/Honda Accord discs, BMW Mini calipers and a simple aluminium bracket. The discs needed a tiny bit of machining on the inner bore to clear the hub, but it was very straightforward. I actually used JCW Cooper S calipers because I had a pair, but the normal ones would work just as well. There's not much to choose between the Mini and Saab calipers but I thought that a current model brake caliper might be easier to find and to get parts for. There is also a good supply of performance pads for the Mini. I've put some more pictures on my journal page for anyone who's interested.

A thought always crosses my mind when I look at custom rear brake lines. I always try to route the portion of my brake lines, whether it be flex or hard line that extend out to caliper/wheel cylinder, across the tube section of the rear housing, so that is it on the backside of the tube, so when I use axle straps to tow the car, or on a raod car, the tow toruck and thier big steel hooks, you don't have to worry about crushing the brake lines, even on street car, resto, this is one item even the biggest purist should vary from the way the factory did it.

Good point. I'll probably re-route them when the axle comes out to fit the LSD.

Here are the pics of this weekends work, the upper links for the rear suspension have been fitted plus holes cut for the shock towers (set up rods inserted at present instead of dampers)

The axle has been up in its final position and A frame aligned

Next the shock towers will be constructed and the anti-roll bar tabs welded to the axle.

A couple more..

Nice Tom,.......Except the track links go inside the axle brackets and the shock mounts go where you have the links. And the sway bar links should align bar hole to anchor hole. Those look like they could be shortened to keep the side arms level. 1/4"-28 thread. Just do the RH end, easy in a lathe.

I've calculated compression ratio and I'll PM. Feel free to post if you want.

Thanks Dave will adjust those things :)-D

The anti-roll bar was a last minute, lets just see roughly what it would look like set up

Tom, PM sent.

Looking good Tom. I'm not really familiar with RB shells, but is the front mount of the top link using the original rear ARB mount?

Dave,

I guess with the axle rotating around the bottom heim joint the roll steer is controlled by the top links. It's hard to tell from the pics but have you designed it with a little bit of roll understeer?

Joe

Well spotted the body side of the upper link does use the anti-roll bar mount but in a very heavily modified form.

As for the roll understeer, what does not come across in the pics is the body side of the upper arm is actually adjustable where it is mounted allowing the roll understeer to be adjusted fairly rapidly.

Tom

Tom,

Out of interest how tall do you think the rear turrets will be?

Dave,

In you opinion how much of an advantage is the rear A frame setup over the standard leaf sprung racer setup with traction bars and an axle location kit?

Joe, i could tell you the exact height of the upper shock eyelet and therefore the turrets but I'm not with the car at the moment, basically with the car at race ride height and the axle at operating height, with the race wheels and tyres on the car the upper shock mounting brackets will be 1-2" above the rear wheel arch mouldings on the inside of the car. I know thats tall but the rear dampers we are using are quite long and that mounting bracket height is with the dampers at 60/40 travel. The set up rod in the picture is the operating length of the damper so that can be attached to the lower mount and when the body and axle height is set this dictates where the upper mounting bracket has to go.

Tom

Joe, two major advantages: getting rid of the leaf springs and Armstrong shocks is a "BIG" weight reduction, and ability to very easily adjust roll steer and corner weights with the coil over. Biggest disadvantage is cornering side loads come into the center of the axle where the A-frame attaches and must be accounted for.

Joe, PM sent.

For interest these are the early set up photos for the top mount of the rear dampers, Pics show the first bracket placed in position, will post more photos as the bracing and support elements are fitted:)

As you can probably tell we are going slightly against convention and not actually using shock towers at all.

The v high tensile steel bar you can see will be heavily braced, to resist any vertical or torsional forces. By having this design for mounting the dampers we hope to reduce over all weight (since we are incorporating it into the roll bar structure and not having to build v tall steel towers) and allow easier adjustment and greater visibility of the suspension set up

As for sealing the underside/rear of the car from then driver(which is obviously easier with enclosed shock towers and/or a roadster) we will be blanking off most of rear boot space with thin aluminium sheeting plus access hatches.

Tom, be sure to cycle the axle through full ride and roll W/O the springs to make sure things clear and no rubs.:)-D

Thanks Dave will do

We did that 2 or 3 times over the weekend when we first placed the axle on the A frame and upper links but will definitly be checking everything over many more times before its all bolted up :)

Tom, exciting that you have now reached this stage. I am hauling the B out to Dave's this weekend --1100 miles each way---and will leave it with him for the week while my wife and some friends and I ski. He will install his vintage spec suspension, some of Peter's C's excellent race shocks, and a hybrid rear end, and then set it all up.

If he lets me, I will post some pictures of Dave and his workplace. Thought you and others might like to see this, if he is OK with that. I have the same curiosity about Hap and his environs---wanting to connect a face and physical space and add another dimension to all these, these words .

Tom,

The MSA blue book has a few updates for 2012 around body/chassis that you may not be aware of. Paragraph 5.2.1 section J. How I read this is that you must enclose all suspension parts from the drivers compartment. So you need some sort of box around the suspension parts.

James thanks for mentioning but all suspension parts front and rear will be separate from the drivers compartment. We are just not using load bearing shock towers.

There will be pics later ;)

Sorry about the slow reply to your last post, I would imagine the engine will be actually with us within the next 1 to 2 months. As for set up we are just having a think about that actually, I will be having a chat with Peter to see if hes keen on chassis dynoing the car/engine, I want to check first because the engine will be running Daves crank fired ignition, dry sump ect

I will try an make the April race meet, but it'll be watching only! Will you be going?

Tom,
Yes I'll be at the Donnington meeting competing in the Peter Best Championship for 2012.
I missed the class championship by 1 point last year so hoping to do better this time round.

If your there look out for my car and come and say hi.

If your feeling like a weekend of racing you could always travel from Donington on the Sunday to Castle Combe on the Bank Holiday Monday. I'm entered in the HRDC MGB50 race.

Good luck at Donington James. I can't make it because of the Combe race the next day.

Thanks Joe.

Enjoy Combe. Hope your FIA car goes well. Such a shame we didn't get there this year. Your home track so you should do well.

James

Thanks Joe

If I'm not working i will try and make both days, should be fun

If i miss one or the other best of luck to both of you

Tom

Don,

That sounds really great i would have loved to send the car to Dave to get him to check everything over but may have been a little pricey!

Your going to end up with a pretty awesome car there, please also post/send some pics of your car too

Your engine or at least parts of it are from Dave aren't they? if so i would be keen on sharing any dyno/setup info or how different parts I'm running and your not or the reverse perform. It might be of benefit to both of us if your keen that is?

Tom

Yea I'm sure your right Don I wasn't sure of the exact spec of your engine.

I'm looking forward to comparing the HIF6s and 48 weber on the dyno.

An its certainly quite a family if you include our cars too!

I have a minor correction to Don's last post. His DCOE manifold is all FAB-TEK, long runner casting from TWM(now discontinued) and all contouring/machining done in my shop. His was made from the very last of the about to be scrapped(by TWM) castings that I bought several years ago because I really liked the design.

I have accumulated a diverse collection of DCOE manifolds. The least favorable one (IMO) is the short runner TWM although this one fits on an MGA I am Told.

The ones I like most from a design perspective are the Oselli, Pierce, and Warneford(sp?)which may no longer be made. If Someone knows otherwise, please let me know. The Pierce is the longest but I'm not sure about vehicle fit.

Dave,

If you click on the link below you will see the MGB (right hand drive only) manifold that is readily available from Moss. How does this compare to the old TWM design?

http://mangoletsimanifolds.com/manifolds/mg.html

Joe, from the picture and dimensions that looks good. I suspect that RH drive only is because of the linkage or power brake interference which is not an issue with a race car.:)-D