ProjectLMP
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| posted on 18/1/03 at 07:15 PM |
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Chassis model complete
I have finished the chassis model and posted more pictures and text on the web site.
Home of the Astronomicalcost Mid engined LMP project
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Rorty
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| posted on 19/1/03 at 03:23 AM |
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Very nice model too. Any idea of amount and dimensions of the "tube" used? It would be interesting to calculate the real weight of the chassis.
It looks like you could build it out of PVC pipe, and it would be strong enough.
As mentioned with the gecko chassis, have you tried a torsional test? What happens when the test is repeated after some elements are removed?
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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BasOlij
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 posted on 19/1/03 at 09:30 AM |
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Loooking good!
Hmm I believe I am running behind now:-)
Greetz,
Bastiaan Olij
1984 Porsche 944 type 2
1981 Delorean DMC-12
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fastenuff
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| posted on 19/1/03 at 11:17 AM |
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Looks very very very well triangulated, even double along the passenger compartment.
Probably the chasis will be heavy. but in the end you have to feel good about the car when driving it.
If i was goin this route I'd loose the outside runners on the compartment or make them in a smaller dimension as the rest of the chasis.
happy motoring
[Edited on 19/1/03 by fastenuff]
Ingmar
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Spyderman
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 posted on 19/1/03 at 01:47 PM |
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quote:
Originally posted by fastenuff
If i was goin this route I'd loose the outside runners on the compartment or make them in a smaller dimension as the rest of the chasis.
happy motoring
[Edited on 19/1/03 by fastenuff]
I would do the opposite!
I would make sideriggers stronger and maybe loose a bit of weight elsewhere with smaler tubes in crossbracing.
It would be interesting to do a crush test on chassis to compare load bearing in different directions.
At a wild guess I would predict that it would take in excess of 10 times more loading front to back as side to side.
Rory would your FEA do this sort of thing?
Just curious!
Terry
ps. LMP very impressive, but would question scale of tubes used. Looks a bit over-engineeered.
Just my humble opinion of course!
Spyderman
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ProjectLMP
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| posted on 19/1/03 at 02:07 PM |
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Rorty, Thanks I guess all the hours I spent building balsa airplanes when I was younger have turned out to be useful.
I have done lots of experimenting by removing different elements and comparing the stiffness. There are a few I could remove but they are there for
reasons other than pure torsional strength i.e.
. Mounting points for shocks, rear wing pylon
. Side impact protection
The side pontoons while looking somewhat redundant, added significantly to the stiffness around the open cockpit area. Without them it was pretty
flexible. Rear of the cockpit they still make a difference although less so. I guess I could remove them there but it would only save around 5 lbs.
I plan on using a combination of 1 1/4, 1, 3/4 round and square 16G. I am already a head of you on the weight estimation. I numbered and colour coded
each element depending on tube type and size. I have then entered this into a spreadsheet along with the length of each element. By changing a few
numbers I can see what effect changing tube sizes/type has on the overall weight. I will post the results later today.
Home of the Astronomicalcost Mid engined LMP project
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Alan B
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| posted on 19/1/03 at 02:42 PM |
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Paul, looks good, very good.
I agree with the "over-triangulated" comments...you know, were you have 2 diagonals in square where 1 would work.
HOWEVER, I'm inclined to do the same too, so I don't intend to be critical....a few extra pounds hurt less than the consquences of being too
flimsy......and your point about side impact and mountings is well understood.
I'm still reviewing my chassis, with changes in mind to lighten, strengthen and stiffen.....oh and simplify too where possible.
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ProjectLMP
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| posted on 19/1/03 at 02:55 PM |
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I have a tendency to over engineer. Some of the X bracing did make a measurable difference to stiffness. I calculated that I could save about 5 - 7lbs
if I removed it completely. For the sake of a bit of extra safety is doesn't really seem worth removing to me. There are other less critical areas I
can save that weight on.
Home of the Astronomicalcost Mid engined LMP project
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fastenuff
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| posted on 19/1/03 at 07:46 PM |
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that is what i meant you have to do what you feel safe in. I'm planning on oversizing tubes aswell, to get some xtra protection from the side, Not
that I ever hope to get hit by anythig in the future, but better safe then sorry
Ingmar
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document
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| posted on 23/1/03 at 04:02 AM |
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Very nice model. Glad I found this forum -- lots of people thinking along similar lines to my own, and most of them quite a bit further along than I
am. I'm with you, LMP, in that I love the idea of a street legal prototype sports car.
One quick question for now: What constraints drove you to design the side pod as a triangular prism? I've been planning on the same idea, only with
a full rectangular cross section. Hopefully that and a full cage would give me at least a shot of keeping a soccer mom with three tons of lincoln
navigator out of my hair (er, well, in that case I'm probably screwed, but you get the idea..). Anyway, the greatest protection in your design
appears to be about four inches off the ground, where it will do the least potential good in a side impact.
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ProjectLMP
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| posted on 24/1/03 at 03:07 AM |
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I was originally going with the square side pods and agree about the extra protection they offer. The main reasons for going with the triangular pods
were to save weight, body clearance issues and stiffen the cockpit opening. On the real frame they will be wider than the model so will offer a bit
more protection.
The big problem with a car like this is that it is so low that a normal sized SUV would take your head off. Mine is more of a track car so I am more
worried about hitting barriers than other cars. If I was to use it seriously on the road, some form of cage would be good. However, I don't think
they are legal here in Canada.
Home of the Astronomicalcost Mid engined LMP project
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