TableLeg
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| posted on 13/2/14 at 10:00 AM |
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Removable chassis rail???
Hi all,
I hope somebody with chassis/welding experience can help me answer a question.
I am at work so don't have access to any pictures to help explain this.
I am trying to modify a chassis.
The top tube that spans the width of the chassis at the front top of the footwell.
Could the centre piece that essentially forms the upper tube to the transmission tunnel be cut out (leaving the remaining tubes above each footwell)
and made to be removable so that it could be reattached (i.e.bolted in) and still provide the same strength to the chassis?
I really need this tube out of the way to aid transmission fit but obviously don't want to weld it back in afterwards.
Could it be done and if so how?
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Thetom
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| posted on 13/2/14 at 10:30 AM |
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Obviously not quite the same thing but the gearbox cross member on a land rover is bolted in. Two 8"X4" or so chassis rails running front
to back and a 4" tube with bolting flanges either end on the gearbox member. I'm sure it could be done in principle but you would need
suitable flanges either end...and your right a picture would really help!
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adithorp
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| posted on 13/2/14 at 10:32 AM |
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I should think so. I'd want to add fairly substantial brackets, forming webs across the corners of the other tubes, for it to bolt to; You
wouldn't just want a couple of bolts through the tubes.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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James
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| posted on 13/2/14 at 10:42 AM |
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Is it a Locost/7 chassis?
What engine/gearbox combo are you trying to use that would require this?
I chopped out a section of the tube at the end of the footwell/firewall to allow the Type9 to fit further back, but I welded a longer piece back in
over the top so I kept the strength but that bit of the tube was just 1" higher.
Cheers,
James
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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TableLeg
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| posted on 13/2/14 at 11:19 AM |
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Thanks all,
The fact you haven't ruled it out completely is promising.
I figure that if I were to have steel plate welded to the chassis at the point where the removable tube would be, then matching plate on the ends of
the removable tube I could also add some triangulation to the removable tube also secured by plated ends.
Thanks again.
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mcerd1
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| posted on 13/2/14 at 12:55 PM |
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it would still be best if you didn't have to go down this route...
do you have any pic's of the issue you're having ?
maybe we'll hbe able to suggest something else....
[Edited on 13/2/2014 by mcerd1]
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britishtrident
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| posted on 13/2/14 at 12:58 PM |
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Yes --- here is the 50cent explanation.
All Seven and Locost style cars (with well known exceptions) style cars use spaceframe chassis.
In a pure spaceframe all members in the chassis are either what engineers call ties or struts that means that the loads going through a member are
applied at the ends.
In the case of a tie the member is under tension being stretched like just a rope.
In the case of a strut it is being squeezed by pushing on the ends, like a stone column support an ancient Greek building.
In fact in a car chassis space frame because the car accelerates, brakes and corners most chassis members sometimes act as ties and at other times the
load reverses and they act as struts.
In theory any member in a pure space frame could be cut out and replaced by a member with pinned ends, in our car building terms an example of
this would be a tie bar with Rose jointed ends.
In a car space frame chassis we have to provide a clear space for the engine and passengers and also mounting points for engine, gearbox and
suspension so a spaceframe car chassis can never be a true space frame as some chassis members will take have some bending loads.
The member you wish to alter however acts a a pure tie/pure strut so in theory it can be be replaced by a simple tube with pin jointed ends.
However being a belt and braces guy I would also add another welded in tube further back in the transmission tunnel.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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motorcycle_mayhem
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| posted on 13/2/14 at 02:00 PM |
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I'd have no issues substituting a bolt-on member for the top rail, if you have a typical 7 layout.
On my BEC (Westfield) I welded a member on the bottom of the tunnel entry, since I needed no bottom entry. Looking at the chassis I could see two
footwell 'halves' that were otherwise unconnected at the bottom. Point of saying all this, is that if you're doing things from the
top, why not similarly weld a bit across the bottom.
The round tube triangulating diagonal on the engine bay side (somewhat important) was also replaced with a bolt-on member, due to a need for turbo
access. This is was then left off (I can hear the armchair nannies from here) for a lot of the car's last season, with no detriment to lap
times. I guess if I'd have hit the wall the car would have folded easily.
Thing is, its my belief that the car, per se, is somewhat over engineered anyway. However, BECs apart, if you've put a Chevy 5 litre in it,
don't stop at 16 gauge 1"... Looking at some of our American cousins (big people with even bigger engines) you can see why they go for
such massive steelwork.
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Nickp
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| posted on 13/2/14 at 04:46 PM |
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I did this to allow my BMW gearbox to fit-
And lowered the bottom rail also (I know this can be removed but I wanted it in)-
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jacko
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| posted on 13/2/14 at 04:51 PM |
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This is a mk indy chassis my car ]
it dose not have a rail across as you can see
 
engine
Jacko
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TableLeg
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| posted on 13/2/14 at 04:52 PM |
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quote:
Originally posted by Nickp
I did this to allow my BMW gearbox to fit-
Thanks for that, That's very similar to what I was thinking of doing except to weld it in.
EDIT:
The more I look at this the more I think this would help me no end. Just that bit extra room removed from the front rail would help me a lot.
Thanks again for this.
[Edited on 13/2/14 by TableLeg]
[Edited on 13/2/14 by TableLeg]
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TableLeg
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| posted on 13/2/14 at 05:16 PM |
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quote:
Originally posted by jacko
This is a mk indy chassis my car ]
it dose not have a rail across as you can see
engine
Jacko
Thanks for that too.
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TableLeg
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| posted on 13/2/14 at 07:17 PM |
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Would this work equally as well?
https://www.dropbox.com/s/52ozrst4xqks3b6/ChassisMod1.jpg
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jacko
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| posted on 13/2/14 at 07:29 PM |
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Yes, Don't you like where my battery is 
Jacko
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The Black Flash
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| posted on 19/2/14 at 09:31 PM |
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Dax did the same to my chassis to fit the larger gearbox in - top rail is kinked much the same as NickP's approach:
Still a complete pig to get in though! The number of times I wished it had an extra inch of clearance...
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TableLeg
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| posted on 19/2/14 at 09:36 PM |
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quote:
Originally posted by The Black Flash
Dax did the same to my chassis to fit the larger gearbox in - top rail is kinked much the same as NickP's approach:
Still a complete pig to get in though! The number of times I wished it had an extra inch of clearance...
Thanks for that info Black Flash.
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