TheGecko
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| posted on 15/1/03 at 02:40 PM |
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Chassis design progress
Hi all,
I started making a 1:6 scale balsa chassis model ages ago but stopped to work on the styling model instead. Now I've come back to the chassis as I
try to finalise the design.
Comments? (polite ones please  Floor and firewall/seatback will be welded steel (20g?) with some stiffening ribs folded into the floor which will
also be seat mounts. The side pods will be clad in bonded and riveted aluminium. There's still some work to be done around the front suspension bay
and there's (fairly obviously no rear yet.
Dominic
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ProjectLMP
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| posted on 15/1/03 at 04:03 PM |
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Looks good with plenty of triangulation. The only comment I would make is that maybe with a few changes you could get away with a few less tubes
connected to the dash area. However, if weight isn't an issue then I'd leave it the way it is.
Home of the Astronomicalcost Mid engined LMP project
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fastenuff
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| posted on 15/1/03 at 07:29 PM |
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the triangulation is closely related to the position of the suspension. I think that you have doubled up some parts of the frame (on the sides
mainly). pick up the chasis model at the load bearing points in the chasis and see how or wether it flexes. ( this is how I would judge the structure
of steel bridges before calculating them, this was some time ago though)
good luck and enjoy
Ingmar
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interestedparty
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| posted on 15/1/03 at 07:51 PM |
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1:6?? are you working in imperial??
Anyway it's a basic rule of spaceframes that the loads should be fed in where three or more tubes join, and this is not the case with your design so
far. The main loads are the top of the spring/shocks assuming you are using conventional wishbone suspension with outboard spring/shocks. I can't see
where the rear suspension is going to attach but I assume the front spring/shocks will mount halfway along the front upper longitudinal tube, and this
area needs to be triangulated or that tube will bend under heavy loading. Easy enough to put right. Excellent model, BTW
John
As some day it may happen that a victim must be found,
I've got a little list-- I've got a little list
Of society offenders who might well be underground,
And who never would be missed-- who never would be missed!
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ProjectLMP
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| posted on 15/1/03 at 08:03 PM |
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I agree with Interestedparty about the front suspension bay. You mentioned that it wasn't complete so I didn't comment. However, looking at the
picture again, do you plan of putting a spare tire in the bay as shown? If so I think you could have some problems without some bracing on the top.
Home of the Astronomicalcost Mid engined LMP project
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TheGecko
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| posted on 16/1/03 at 01:04 AM |
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Thanks for the comments so far. A couple of answers to questions:
- 1:6 scale is because the artists model seen in the first photo is 1:6 and beacuse 1:10 is fairly tiresome to work at, especially on the styling
model.
- Front bay. Yes, the spare is intended to go there as shown. The radiator will be in front of the bay, venting through the bonnet (hood) above the
spare. I'm happy that I can brace around it. The battery will be under the spare too to help with weight distribution and keep CofG lower.
- Re triangulation and load points for suspension elements (shocks, wishbones etc) - there're a number of triangulating bars to come in both the top
and sides of the front bay yet. As well, front suspension is intended to be pull-rod, with the bell-cranks pivoted down near the bottom rear corners
of the bay.
- Rear suspension. The model curently finishes at the seat back as I'm still deciding on struts vs de Dion for the rear (de Dion currently
winning). When I've finished the front bay and the back end, I'll post some more images.
Dominic
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Rorty
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| posted on 16/1/03 at 01:40 AM |
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Nice practical model. I think you could almost leave the scuttle area in balsa. You could drive a tank over it without fear of any distortion! IMO you
have too much going on there.
I too would be concerned about the front upper wishbone and shock mount locations. I can't see how you can effectively make that area strong enough
with the spare sitting as illustrated.
It's impossible to tell from your model, what size of tube you plan to use for some of the bracing, but I think on the whole, you possibly have too
much bracing. Two diagonals would suffice in the rear bulkhead instead of four. I also think the diagonals in the side pods are unnecessary.
A model is a fantastic tool for testing parameters, you could try removing various components, one at a time, and observing if there is any
perceivable loss of torsional ridgidity.
Please keep us abreast of any results, and progress too. 
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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TheGecko
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| posted on 17/1/03 at 02:43 AM |
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Thanks to Rorty and everyone else for confirming what I probably already knew - that the thing is more complicated than it needs to be. I'll set
upon it with the saw this weekend and see how much I can remove without catastrophic failure
As the famous aircraft designer Antoine de Saint-Exupery said: "Perfection (in design) is achieved not when there is nothing more to add, but rather
when there is nothing more to take away."
I'll post some updated images when I'm done.
Dominic
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Rorty
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| posted on 18/1/03 at 04:13 AM |
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de Saint-Exupéry actually said;
“You know you've achieved perfection in design, not when you have nothing more to add, but when you have nothing more to take away.”
Sorry to be such a pedantic little 9rick, but it is one of my favourite quotes, which IMO, isn't aired quite enough.
As I said before, I think your approach, with your model, is the right way, and I look forward to further developements.
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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kingr
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| posted on 24/1/03 at 04:58 PM |
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Darn it, you've put my book chassis balsa model to shame. I'll post a pic of it some time.....
Kingr
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kb58
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| posted on 26/1/03 at 04:53 AM |
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At first glance, I'd say too many tubes. Keep in mind if you are installing aluminum paneling, the smaller bays won't need diagonals since the
paneling already serves the purpose.
OTOH, does it really matter? How important is 10lbs worth of tubing, really? Just build it. If you keep second-guessing yourself, waiting until the
design is "perfect", you may as will give up now.... Just build it... it'll be fine... really.
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