1672 replies to this topic

[eyepeeler]

Thanks for the input Vick. If I had a rim to put a tyre on that would help LOL. I ended up going with a diff width of 1495 after talking to the diff bloke.

Mount the tyre to the rim and measure the tyre sidewall to sidewall. You may wish to throw that into the equation.

 

As I want to get the roll cage done (rules changed as posted before) I have mounted the Sub-Frame to get and idea of how it will work in with the roll cage. I tried out the alloy bushes I had made up, happy with the result. Fitting the Sub-Frame is a prick of a job!! Any way I got it done and now I can start working on the cage.

 

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[ls2lxhatch]

Most k-frames have twisted a bit over the years probably due to braking. If you measure the distance between the front and rear bolts at the top of the k-frame then you will probably find the rears are closer together and the fronts are wider apart than the distance between the rails.

 

I jacked my k-frame back into spec and it only takes a couple of minutes to fit. You will find a few more tips on making it easier to fit the k-frame on this webpage.

 

http://ls2lxhatch.co...gineinstall.htm

[eyepeeler]

That's a nice bit of work Col to do that. It would certainly help the cause, unfortunately I can do that within IP rules,

This is the ruling cut and pasted from 3J Specifications:

 

3.1 Strengthening: It is permitted to seam weld the bodyshell. Metal to a thickness of up to 5mm may be added to
fully sprung components to a distance of 75mm from the edge of each suspension pivot point aperture. Such
metal must follow the contour of the original metal at all times. It is not permitted to add or incorporate any
other components which contribute to the rigidity of the bodyshell, other than the safety cage structure as
described in Article 14.1, and a strut tower brace as described in article 9.7.

 

What I am working on is a bar from the sub-frame mount closest to the firewall to the junction of the lateral half roll bar and steering mount bar. It pretty much the same as what Clarke Hopkins did in his NZ CMC Torana except he had bars going to all four sub-frame bolts.

 

Andy, I will be checking the measurements when I take it out. What should it be???

[ls2lxhatch]

Andy, I will be checking the measurements when I take it out. What should it be???

There is a thread where several people have posted the measurements from bolt to bolt on the towers.

My crossmember rebuild

794 mm front and 792 mm rear centre to centre was the result for three k-frames and one 790 mm front and 789 mm rear.

I measured the distance between the holes in my chassis at 31.25" (794 mm). I believe the Torana was designed using imperial measurements.

My theory is that the k-frames started out as 31.25" (794 mm) between the bolts. The braking force has caused the k-frame to twist in the rubbers and move rear bolts to be closer together than the front bolts. I can not think of any other explanation as to why there is a difference between the front and rear bolt spacing.

I stretched the k-frame that was giving me trouble back to 31.25". With the amount of practice I have had installing and removing the k-frame on my hatch I can bolt the k-frame to the body in a couple of minutes.

I would measure the distance between holes the rails on you car first.

Edited by ls2lxhatch, 26 July 2013 - 02:24 AM.

[76lxhatch]

3.1 Strengthening: It is permitted to seam weld the bodyshell. Metal to a thickness of up to 5mm may be added to
fully sprung components to a distance of 75mm from the edge of each suspension pivot point aperture. Such
metal must follow the contour of the original metal at all times. It is not permitted to add or incorporate any
other components which contribute to the rigidity of the bodyshell, other than the safety cage structure as
described in Article 14.1, and a strut tower brace as described in article 9.7.

I don't understand which part of that excludes the above plating idea? As long as its no more than 5mm thick and you keep it 75mm from the control arm pivot (mount), which may be touch and go at the top but doable, it should be OK?

"Metal (...) may be added to fully sprung components (...) not permitted to add or incorporate any other components"

 

Am I reading it wrong?

[Peter UC]

But can only be added around a suspention pivot point. ie around where the wishbone is mounted on the cross member. However I thought they changed the rules so the cage can extend out the passenger compartment like the late model cars can?

[eyepeeler]

I'm certainly no expert on rules but the way this one reads is as follows, I can add the stated material up to 75mm from the suspension pivot point. This is the upper and lower arms not the chassis rail and where the sub-frame bolts to it. It's not permitted to strengthen the body shell in any other way. Except with the roll cage, which is the direction I am heading in as I posted earlier.

 

I don't understand which part of that excludes the above plating idea? As long as its no more than 5mm thick and you keep it 75mm from the control arm pivot (mount), which may be touch and go at the top but doable, it should be OK?

"Metal (...) may be added to fully sprung components (...) not permitted to add or incorporate any other components"

 

Am I reading it wrong?

 

 

But can only be added around a suspention pivot point. ie around where the wishbone is mounted on the cross member. However I thought they changed the rules so the cage can extend out the passenger compartment like the late model cars can?

Hi Peter, yes they have changed the rules to allow the cage outside the passenger compartment. LXSS350 put up a photo of Clarke Hopkins engine bay, What I am going to do is based on this. I will be running 2 bars, not 4 as he has done though.

[76lxhatch]

I could be wrong but it is my understanding that control arms are not "fully sprung", since they are attached to the unsprung components (stub axle etc). If that's true then they can't be talking about plating control arms, the body and chassis would be fully sprung.

 

I do see what you mean though and I guess its possible that the intention of the rules is to allow plating of control arms, even if that's not technically what it says...?

[eyepeeler]

 Unsprung components include rims, tyres, stub axels, brake calipers and rotors, wheel bearing, hubs, springs, shocks and the suspension links which are in this case the upper and lower control arms.

http://en.wikipedia....i/Unsprung_mass

 

As the rule is 75mm from pivot point on fully sprung components, this means that the sub-frame can be plated. It also means the area around the diff trailing arm mounts on the chassis can be plated.

 

At least that's the way I read it. Gotta love rules...... the debates are endless and lost in interpretation sometimes!! Good stuff.

 

I could be wrong but it is my understanding that control arms are not "fully sprung", since they are attached to the unsprung components (stub axle etc). If that's true then they can't be talking about plating control arms, the body and chassis would be fully sprung.

 

I do see what you mean though and I guess its possible that the intention of the rules is to allow plating of control arms, even if that's not technically what it says...?

[76lxhatch]

Exactly, the way I read it that rule is intended to say you can strengthen existing structure a bit but you can't add additional bracing (e.g. chassis connectors etc) other than a roll cage. It would be really nice if you could plate the subframe and on the face of it that seems possible.

 

The only thing I'd be a little wary of is that it says "pivot point aperture" rather than just pivot point; the upper control arm pivot doesn't have a clearly defined opening like the bottom one so it could be a little open to interpretation as to how close you can get, and you want to get as close as possible.

[eyepeeler]

Just started to fabricate the front bars to the sub-frame bolts. Just the initial set up at the moment, will trim and tidy up and get it ready.

Give you an indication of what I want to do anyway.

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[eyepeeler]

Both sides mocked up. I will also be putting a bar in from the cage mount up to this bar just behind the firewall.

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If you're wondering what tool I have been using to notch the tube, this is it. Made by JD2, it is an awesome bit of kit.

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[warrenm]

Where do I get one.

http://jd2.com.au/no...otchmaster.html

[ls2lxhatch]

I suspect the rear k-frame mount would be under more load than the front k-frame mount under braking. Most of the k-frames I have measured appear to have twisted in at the rear. (rear bolts are closer together than the front)

Edited by ls2lxhatch, 01 August 2013 - 11:46 AM.

[eyepeeler]

The reason is a simple one, the bar wouldn't clear the wheel tub if I went to the front mount and I couldn't get the angle right. I will take the advantage that Andy has said about it being the better spot though!!!!

Is there a reason you dont go to the front K-frame mount ??

 

 

I suspect the rear k-frame mount would be under more load than the front k-frame mount under braking. Most of the k-frames I have measured appear to have twisted in at the rear. (rear bolts are closer together than the front)

 

I have got all the trimming done and ready to weld it all up. Pretty happy with the way it looks.

 

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[dattoman]

Are you not allowed to run a flat plate on that area and brace the whole bit... sort of like Welbys but abit more plate ?

 

 

[eyepeeler]

Are you not allowed to run a flat plate on that area and brace the whole bit... sort of like Welbys but abit more plate ?

 

 

 

 

Hi Neil, I was hoping you would look at what I was up to. I was going to get in touch with you about rear end Superpro bushes and a bush for what I am doing here. As you saw, I had the alloy bushes made up to go between the sub-frame and the chassis rail, and this set up that I have just fully welded in has the tube go down to the mount hole. What I want to ask you is can you get a nolethane bush made up to fit the ID of the tube which when the subframe is in, will squeeze and tighten up against the alloy bush underneath.

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The reason I went this way instead of the way Welby did it, was this way I had bars going directly to the point and was part of the assembly that the sub-frame bolted to. I did look at the we he did it and I like the Hopkins Torana idea, so I went that way.