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MG Midget and Sprite Technical - Boot seperator as a chassis stiffener?

Morning all.

I've been having ideas again. Whilst I know most of them come to nothing, this one I thought I'd ask the collective about.

As part of my Sprite rebuild and massive upgrade plan I am part way through fitting a coil over De-Dion back end under the car. This has left me with two towers that are extensions to the chassis rails which sit at the top of the axle hump. Please have a look at the Rear Suspension progress thread in the 16V section for more details and pictures.

As I'm going along, the shell is getting a few stiffening plates and so on fitted, and I'm thinking about making a backbone frame for the transmission tunnel too. And having seen the below pic, I got to thinking about fitting a similar web between the two towers. It would pretty much replace the boot separator but with the intention of helping stiffen the back end of the car up a little. It would be welded to both towers as well as the bit that hangs down under the roof lip bit. I'm sure it has a better name than that, but I can't think of one right now!

So what do you think? Would it help? And is it worth the effort, as making the web would probably take a day or so to do properly.

S Overy

Should also have said that it will be welded to the small lip that goes along the top of the axle hump.
S Overy

I have a welded in boot seperator (PO said it had raced?)
And have no complaints about shell stifness.
Mine is a flat plate but that is because it is a mkII

One added bonus is my boot is safe when I lock it where you can usualy just go through the cardboard
Onno K

Good point about the security aspect, I hadn't thought of that.

Would you say it makes any real difference to the shell, or not enough to notice?
S Overy

Well my previous midget was so rotten the change was amazing..
But compared to a good midget it is not that big.
Though several people have commented on the nice ride (not comfort ;) )
Onno K

you'd probably need the thoughts of those that use the car for sport (possibly they're not allowed under the sport rules I've no idea)

well at least it's 'a bump'
Nigel Atkins

I think what I have fitted is what you mean. It's been done on my car as a firewall but I did think it would aid in strengthening the shell. It's ally and was made by using the old cardboard one as a template. As you can see it's bolted in. As for telling the difference from fitting something like that then I think you are expecting too much. It's going to help but I would doubt you would notice.

I would do it the same way if I were you. Steel would be very heavy and if welded in you wouldn't be able to remove it easily. It's a very good safety feature for a road car from a firewall point of view.

John

John Payne

Thanks for the ideas.

John, have you ever needed to remove your firewall? I'd prefer to do it in steel, partly because that's what I have lying about and partly because I'd have to weld in tabs to bolt it to anyway, so I may as well just weld the thing in anyway. A 20 SWG gauge panel wouldn't weigh much I don't think.
S Overy

Simon

I have a firewall similar to John's in my car, its sealed in, and I have never needed to remove it in the 25 yrs its been fitted. Go for the brace between your turrets IMO.
By the way where abouts are you in Northants ?

Ian
Ian Webb '73 GAN5

I would say with your setup, you will feel a difference using an adjustable strut brace more than anything.

Never pull the towers together using a brace, but push them apart. We used to do quite a bit of development work for the race cars with a well known suspension manufacturer and they cured all sorts of problems by adjusting the brace outwards - namely wet weather driving

The bodywork at the rear is pretty much surplus to requirement, hence we can get away with swapping it all out for fibreglass

As such, a lightweight bulkhead and a brace would be the route I would take.

You could however triangulate the brace to a solid mounting area such as the back of the tunnel where it meets the rear bulkhead, but you're then introducing tube work to an otherwise simple cockpit
PeterJMoore

Ian,

I'm down south of Daventry. Where are you?

Peter,

Good idea about the brace and then a light weight panel. How easy is a brace to construct? Is it worth going to hassle of making it adjustable on the car?
S Overy

Simon
I am in Brixworth, not to far away could I come over and take a look at your project ?
Ian
Ian Webb '73 GAN5

http://img513.imageshack.us/img513/9010/1327614708614.jpg

This is the general idea Simon

A bar linking the two turrets with a form of adjustment linking the two halves
P Moore

Ian,

Course you can! Although my garage/workshop is a little bit dusty and grubby so a change of clothes or boilersuit would be advised. E-mail me to sort something out.

P Moore,

That's pretty much what I had in mind. And fitting something across the tower tops wouldn't be too hard to sort out either. And making it adjustable is dead easy with a LH and a RH threaded rose joint at either end.

S Overy

Peter,

The cars you had the strut brace fitted to, did they have coil overs or strut suspension. I can see where they would make a difference on a car using struts but not with the coil overs as S Overy is using.
David Billington

it will make a difference, purely by tying both upper shock mounts together, introducing more rigidity and therefore more feel through the ar*e dyno.

We were running coilover systems in a car that originally used Macpherson struts in the front and double wishbones in the rear.

No matter what way you look at it - introducing any form of chassis bracing between suspension mounts will allow the suspension to do its job and rely less on the felx in the metalwork surrounding it.
PeterJMoore

This thread was discussed between 25/01/2012 and 27/01/2012

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