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Bolt on front end?

MK9R - 1/10/09 at 07:17 AM

Was looking at the front of the chassis making plans on where to cut it to start the rebuild. Looking at the damaged/repaired tubes it looks like the best place to cut will be just behind the rear lower wishbone mount, where there is a vertical upright between the upper and lower chassis rails. I can then make a new front end on the bench and join it back onto the chassis when complete. I was thinking the best way to join the main chassis rails would be to get a solid insert machined that would slide inside the the chassis tubes between the join, then the do the necessary welding. But then we (well dad) had a thought, why not close off the chopped off front of the main chassis (cross members, triangulation) and have 2 flat plates either side which then bolt to flat plates on the front section of the chassis (which house all suspension). This would make future suspension damage repairs easy as i could just build a new front section and bolt it on, i could almost have a spare front end to take to meets incase of an incident.

The car is a fisher fury with lowered race chassis by the way.

Any thoughts?? Any cars out there with a similiar setup?

Mr Whippy - 1/10/09 at 07:30 AM

I think a drawing of what you propose would be a good idea.

Nothing against it, as its similar to the F1 cars with their bolt on rear ends. My main concern would be the bolts being ripped out the brackets earlier than the original tube would have failed so I think the brackets would have to be quite substantial to be totally safe.

Staple balls - 1/10/09 at 07:44 AM

What about alignment?

My gut feeling is you'll be introducing a lot of joints made to locost tolerances, so might end up with some interesting handling quirks.

MK9R - 1/10/09 at 07:57 AM

A very simple mock up (no suspension pick ups and chassis tubes not all shown)

MK9R - 1/10/09 at 07:59 AM

quote:
Originally posted by Staple balls
What about alignment?

My gut feeling is you'll be introducing a lot of joints made to locost tolerances, so might end up with some interesting handling quirks.

It will be easier to get the front end accurate on the bench, then spend some time lining up the assembly with the main chassis before bolting it together. Should be far easier to get accurate this way than trying to weld directly onto the existing chassis (which won't be bare by the way)

iank - 1/10/09 at 08:06 AM

In theory if you make a significant modification to the chassis design during a repair/rebuilt then you'll need to re-IVA the car.

I say in theory because it would be rather difficult for anyone to prove it wasn't like that for the original test.

MK9R - 1/10/09 at 08:07 AM

quote:
Originally posted by iank
In theory if you make a significant modification to the chassis design during a repair/rebuilt then you'll need to re-IVA the car.

I say in theory because it would be rather difficult for anyone to prove it wasn't like that for the original test.

car isn't road registered, so doesn't matter

iank - 1/10/09 at 08:13 AM

quote:
Originally posted by MK9R

quote:
Originally posted by iank
In theory if you make a significant modification to the chassis design during a repair/rebuilt then you'll need to re-IVA the car.

I say in theory because it would be rather difficult for anyone to prove it wasn't like that for the original test.

car isn't road registered, so doesn't matter

Excellent

brianthemagical - 1/10/09 at 08:26 AM

I'd say it sounds like a good idea. I was shocked when i first saw how old school F1 chassis were bolted together, they looked as though they'd fall apart.

How accurate are your building faccilities? You could just have some kind of pin or overlapping brackets to line everything up, making up a jig to keep future parts the same.

As for strength, it should be fine. Most of the bolts would be in single shear for most of the time. The main problem would be keeping it all rigid as both sections are losing a lot of their support. Also, there will be a small weight increase.

One advantage would be that you'll be able to test differnt designs, such wishbone lengths and mounting positions and triangulation.

MK9R - 1/10/09 at 08:35 AM

quote:
Originally posted by brianthemagical

How accurate are your building faccilities?

Standard locost builder in the garage, use a wooden base and clamp down all tubes before tack welding. Will be accurate enough for this job. Alignment can be done using strings spirit levels etc, but then the geo set up can dial out any small inaccuracy.

quote:
Originally posted by brianthemagical

As for strength, it should be fine. Most of the bolts would be in single shear for most of the time. The main problem would be keeping it all rigid as both sections are losing a lot of their support. Also, there will be a small weight increase.

I would expect the chassis to be stiffer, as at the moment there is nothing substantial between the chassis rails between the engine and suspension, this way there would be a sbstantial amount of cross bracing, so hopefully redce the twisting. Yes definetly a small weight increase. Currently myself and car are 536kg, so only 6kg over the minimum, weight, so if does increase slightly no real problem. But then again i am getting new body work this winter and could order the lightweight race version, this would offset the increase in chassis weight

rallyingden - 1/10/09 at 08:40 AM

What about steering column ?

Also with all that strengthening at the nose, next shunt you have will simply bend main chassis further back.

RD

MK9R - 1/10/09 at 08:44 AM

quote:
Originally posted by rallyingden
What about steering column ?

Also with all that strengthening at the nose, next shunt you have will simply bend main chassis further back.

RD

Steering column fits, just the mock up picture is only a representation of the theory.

I understand what you say about it bending main chassis, i would have to design the front to be as sacrificial as possible.

nick205 - 1/10/09 at 09:51 AM

Nothing wrong with bolt on subframes - the E-Type is one example where the whole front end from the passenger bulkhead is a bolt on assembly.

The suqareness and alignment will require some careful work, but not beyond locost fabrication.

One thought.....looking at you're model I suspect any front end impact might generate chassis damage further back as the sub-frame itself will be pretty stiff.

TimC - 1/10/09 at 09:55 AM

Isn't your degree in this type of stuff? Its a very interesting idea.

Is there a Fury on the RGB grid that is anything like the original anymore?

MK9R - 1/10/09 at 09:56 AM

quote:
Originally posted by nick205
Nothing wrong with bolt on subframes - the E-Type is one example where the whole front end from the passenger bulkhead is a bolt on assembly.

The suqareness and alignment will require some careful work, but not beyond locost fabrication.

One thought.....looking at you're model I suspect any front end impact might generate chassis damage further back as the sub-frame itself will be pretty stiff.

its just a representation, will do proper design that takes this into account

MK9R - 1/10/09 at 09:58 AM

quote:
Originally posted by TimC
Isn't your degree in this type of stuff? Its a very interesting idea.

Is there a Fury on the RGB grid that is anything like the original anymore?

I did aerospace, so suppose it had similar things i could apply, but it was a long time ago and my brain is now mush.

No standard furys left, they all fell apart or got destroyed

andyharding - 1/10/09 at 10:50 AM

I like the idea but not the design at all.

Think about the reason a spaceframe is as strong as it is, tubes in compression and tension how they are strongest. Instead of bolting 2 flat plates together at the joint which will be heavy and I think flex unless it's very thick plate why not join the main tubes by having an insert in one half that slides up the other and then a bolt through with compression tube? Keeps everything light and strong.

MK9R - 1/10/09 at 11:02 AM

quote:
Originally posted by andyharding
I like the idea but not the design at all.

Think about the reason a spaceframe is as strong as it is, tubes in compression and tension how they are strongest. Instead of bolting 2 flat plates together at the joint which will be heavy and I think flex unless it's very thick plate why not join the main tubes by having an insert in one half that slides up the other and then a bolt through with compression tube? Keeps everything light and strong.

Point taken.
This is a picture of the fastest car in RGB at the moment, i like! Will be speaking to Derek and having a nose at the car at our next meet

nick205 - 1/10/09 at 11:36 AM

^^^^^^

Tha looks rather nice!

Canada EH! - 1/10/09 at 06:22 PM

It also means that the next prang goes into the plate structure, which is also replacable.