Ginetta G15 Restoration

[John Bonnett]

I'm at a bit of a cross roads with the chassis. Having fitted the seats I now realise that the supplementary bracing shown in my previous post won't work for me because the frame joins the chassis in the middle of the seat runner. I could get round that by fitting smaller seats but I would prefer to keep the originals. For sure the design of the chassis leaves a lot to be desired having little or no triangulation or stiffening. Anything I do to improve things will of necessity mean cutting out pieces of the floor and rear firewall to give clearance for the additional tubes. The shell is so good I don't want to mutilate it. So what to do? Put it together as it is in the knowledge that the car will handle very badly? Fit bracing and cut the body to suit? Or a third option build a new body.

While considering these options, I've been making up fixings for the seat runners. The Ginetta way is to drill a 1/4" hole all the way through the two by two and fit a nut and bolt without a crush tube. What I've done is to weld a 1/4"UNF nut to a length of 10mm stainless tube. Turn the nut down to 10mm and TIG weld the assembly into the chassis.

[byakk0]

what about running the bracing under the seat, and then up behind the seat? Leaving room for adjustment, if those seats have any.

[John Bonnett]

Somehow or other Hazen I've got to try to stop the chassis from wanting to fold up and to put some torsional stiffness in. At the moment I'm thinking about a transmission tunnel that will provide a backbone, taking the load path from the the cantilever at the rear to the front of the chassis. To achieve this the rear firewall will need removing along with a longitudinal section of the floor.

I'm waiting to hear from the GOC how they would view a G15 with an aluminium body. If they are okay with that and accept it as a G15 I can add strength to the chassis and build the body to suit. I would prefer this route rather than having to mutilate a perfectly good fibreglass body.

[vitesse 68]

Hi just picked up on this thread very interesting and what a good project and work so far , I do like reading about other projects / restorations  and at the end of the day we are all here to help in some way  , keep up the hard work both John and the club cheers Pete

[John Bonnett]

Quoted from vitesse 68

Hi just picked up on this thread very interesting and what a good project and work so far , I do like reading about other projects / restorations  and at the end of the day we are all here to help in some way  , keep up the hard work both John and the club cheers Pete

Thank you very much Pete. There were many dark days on the Triumph project and the encouragement I received here made a huge difference to me.

The Ginetta people all seem to agree that the G15 corners really well but the handling ranges from bad to awful. Looking at the chassis it's not hard to understand the reasons. That's why I'm putting the effort into stiffening it up.

John

[byakk0]

That would make sense, John.
Guess I'm not much of a frame engineer. I tend to fly by the seat of my pants more often than not. I'll wait and see how you solve the problem.
Making another aluminum shell will be fascinating to watch again, should you go that route. If I lived closer I'd come run a camera for you to get some good videos of the master at work.  
But, alas, Idaho is a little far for a quick jaunt.

[John Bonnett]

Quoted from byakk0

That would make sense, John.
Guess I'm not much of a frame engineer. I tend to fly by the seat of my pants more often than not. I'll wait and see how you solve the problem.
Making another aluminum shell will be fascinating to watch again, should you go that route. If I lived closer I'd come run a camera for you to get some good videos of the master at work.  
But, alas, Idaho is a little far for a quick jaunt.

Master absolutely not Hazen but if you fancy a foray over here you'd be very welcome, camera or not.

John

[John Bonnett]

I'm adding a cross member between the wishbone mounts which I felt was badly needed. Cut outs were necessary to clear the coolant pipes. Using a hole saw I bored two 40mm holes and TIG welded in stainless steel tubes of the same diameter. This will put a lot of strength back into the box section.

[chunky63]

Hi John,

Another great thread started, got this bookmarked now.
I had a G15 back in the mid 80's it had a race tuned Hartwell 998 and when 'on the cam' went like a scolded cat, great fun 😉

If I remember it had Beetle front bumper that was cut in half (hence the capping piece in the centre) and a Riley Elf rear bumper. If you don't already have a copy its worth getting hold of 'G15 Super Profile' by John Rose.....

https://www.amazon.co.uk/Ginetta-Super-Profile-John-Rose/dp/0854294961


Cheers
Jon

[John Bonnett]

Quoted from chunky63

Hi John,

Another great thread started, got this bookmarked now.
I had a G15 back in the mid 80's it had a race tuned Hartwell 998 and when 'on the cam' went like a scolded cat, great fun 😉

If I remember it had Beetle front bumper that was cut in half (hence the capping piece in the centre) and a Riley Elf rear bumper. If you don't already have a copy its worth getting hold of 'G15 Super Profile' by John Rose.....

https://www.amazon.co.uk/Ginetta-Super-Profile-John-Rose/dp/0854294961


Cheers
Jon

Jon, nice to hear from you and thank you for the reminder about the book. I've just this minute ordered it.

You are quite right about the bumpers. The Riley Elf rears are hens teeth but I do have one, albeit needing re-chroming. But i may not fit bumpers. I'll wait and see.

I've pretty much made the decision to build a completely new body, mainly in aluminium but supported by a tubular steel frame. This decision makes possible some serious strengthening and bracing work on the chassis which could include a backbone like a transmission tunnel. Meanwhile I've still got to finish welding in the seat fixings and the seat belt captive nuts.

[Jonny-Jimbo]

I have to say John, this is turning into a fantastic build, and really taking the G15 chassis to 'the next level' - due to various regulations etc we couldn't do what you're doing to improve the chassis, although a multi-point roll cage did go a long way to bracing it up.

However, isn't that triangulation on the inner mount going to clash with the coolant pipes that run through the chassis?

[John Bonnett]

Quoted from Jonny-Jimbo

I have to say John, this is turning into a fantastic build, and really taking the G15 chassis to 'the next level' - due to various regulations etc we couldn't do what you're doing to improve the chassis, although a multi-point roll cage did go a long way to bracing it up.

However, isn't that triangulation on the inner mount going to clash with the coolant pipes that run through the chassis?

I have to admit that I'd forgotten all about the pipe but when I remembered after the gussets went in, to my relief the pipe cleared them. Lucky or what?  

[Jonny-Jimbo]

Well ain't that something 😉

Are you using aluminium or copper pipe, and have you welded tubes though all the holes? These can suffer pipe chatter without adequate strapping of the pipes - some people seem to run panel edging round the hole to make the coolant pipes a push fit. With the through holes sleeved though this isn't an option. Some form of tube mount is a good idea.

We had an occasional customer car in with complaints of a rattle, and it was usually the coolant pipe in the chassis... or the crank dropping out!

[John Bonnett]

Quoted from Jonny-Jimbo

Well ain't that something 😉

Are you using aluminium or copper pipe, and have you welded tubes though all the holes? These can suffer pipe chatter without adequate strapping of the pipes - some people seem to run panel edging round the hole to make the coolant pipes a push fit. With the through holes sleeved though this isn't an option. Some form of tube mount is a good idea.

We had an occasional customer car in with complaints of a rattle, and it was usually the coolant pipe in the chassis... or the crank dropping out!

Plan is to use one inch stainless steel tubes for the coolant, welded into the sleeves. These will become stressed chassis members and will, I hope, add something to the stiffness.

[Jonny-Jimbo]

Ah, I see, that would certainly stop them chattering around!

[chunky63]

Imp motors are very susceptible to overheating so the plumbing is crucial to a good cooling system. Getting the water from front rad back to the engine is not an exact science and my G15 and Sunbeam Stiletto had competition systems recommended by David Vizard (remember him from the Mini tuning books

http://www.imps4ever.info/tech/tuners_builders/vizard/ccc-look-in-cooling.html

Here's another helpful link...
http://forum.theimpclub.co.uk/forum_back_phpBB/viewtopic.php?f=33&p=222682

My G15 bonnet had rad ducting similar to a G15S.....

[John Bonnett]

Thank you Jon, interesting that DV recommends 70 degrees which is exactly what my Triumph runs at. I have a 72 degree thermostat.

On the Imp the header tank has full flow but I'm thinking about changing it to the modern system with the header tank connected to the bottom hose and a bleed back from  the thermostat housing. This is what I've done on the Triumph and it works well.

[chunky63]

Note in the picture of the G15 Super S that the engine lid is different than a standard G15. The S is a lid where as the standard is the whole rear end.

The S also had a VW T1 engine+transaxle so could be tuned and modified to over 2 litres....wow that sounds fun

VW being aircooled obviously didnt need a radiator etc

Only a few Super S were built and all shipped to the US.

[Nick Jones]

Quoted from John Bonnett

Plan is to use one inch stainless steel tubes for the coolant, welded into the sleeves. These will become stressed chassis members and will, I hope, add something to the stiffness.

Have you thought about the thermal expansion of the coolant pipes?   Slightly wary of welding them in as a stressed member due to this.  I could see you having issues with cracks at the welds after a few years, which would be resistant to roadside repair!

Nick

[John Bonnett]

Quoted from Nick Jones

Have you thought about the thermal expansion of the coolant pipes?   Slightly wary of welding them in as a stressed member due to this.  I could see you having issues with cracks at the welds after a few years, which would be resistant to roadside repair!

Nick

That's a very good point Nick. I'd not thought of that. But would the expansion at a temperature of less than 100C be significant?

[Nick Jones]

http://static.victaulic.com/assets/uploads/literature/26.02.pdf
Quick and dirty calcs suggest 304ss tube will expand something like 1.25mm per metre between 0ºC and 70ºC range.  The surrounding steel would expand approx 1/3 less even if subject to the same range, but could potentially be 70ºC colder on a winters day.  Not massive.......

Nick

[colmiller]

I'm interested to know what filler wire you plan to use to weld in the stainless rad pipes to your mild steel cross members?

With the inevitable vibration any brittleness in the joint will lead to troublesome stress fractures.

[byakk0]

What about running a double walled pipe through the crossmembers?

[John Bonnett]

Nick has made a very valid point and as a result I'm not going to continue with the idea of welding in the coolant pipes. I'm grateful to him for his timely observation.

On a general note I've never had any trouble with subsequent cracking after welding stainless to mild steel using  309 stainless rods. This extract confirms the practice;


As an example, when joining 304L stainless steel to mild steel, the most commonly recommended filler metal is 309L. During the welding process, the weld becomes diluted with some of the stainless steel from one side of the joint and some of the mild steel from the other side, mixing in material from each side of the weld. The goal is to create a final weld deposit whose chemistry is compatible with each side of the weld joint. Using 309L filler metal achieves this goal when joining 304L stainless steel to mild steel.                      

[Nick Jones]

My concern would not be the quality of welds as such.  More that at the welds you'll have some (mostly compressive probably) forces from thermal expansion in combination with varying forces from various directions due to chassis  flex, which I think is agreed to be likely! This makes cracking at the weld edges rather probable in my view.  I'm also a bit doubtful about whether the tubes would really add all that much to the structure and thus be worth taking the risk of problems.

Nick