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PostPosted: March 22, 2017, 3:17 pm 
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7Fan7 wrote:
It would be great if you could spare 2 minutes to answer this survey, which I'm conducting as part of a university project.

Done.

But I'm hardly your target demographic: I design them, these days, rather than buy them.


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PostPosted: March 28, 2017, 8:44 am 
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Sam_68 wrote:
7Fan7 wrote:
Looks amazing! Check out the chassis I'm working on. Pretty much the front and the back remain with the original steel chassis, but we managed to cut out the middle tub and replace it with carbon fibre. I reckon, if it was used in race versions of the car, it could do big damage. We're talking about at least 40kg weight-saving and eventual increase in stiffness. As far as i recall, that middle bit was the weakest in most Lotus 7/Caterham 7 - style kit cars; a side impact would essentially do more than break your ribs even with full roll cage; so thus the reason for designing this carbon fibre tub. Do you think there's a market for it?

http://s200.photobucket.com/user/Sam_68 ... o.jpg.html

Are you working for Westfield/Axon, then? (I took the photo in your link; indeed that's my photobucket account you're linking to).

A weight saving of 40kg seems optimistic; you (if that's your chassis) were claiming a 14kg weight saving over the normal 72kg Westfield chassis, when you presented it at Williams last year?


Hi Sam_68,

Sorry what I meant to say is that the picture (which is apparently yours) is similar to what I'm working on. Sorry about the confusion. But yes I'm currently working with Axon as part of a university project. The figures certainly do look optimistic, but current discussion with them actually unveils that the siffness of the chassis has increased about 30%, 40kg weight saving was inclusive of the rotary engine but if you're looking at the chassis only, it's about 10% weight saving.


I'd appreciate if you could take the time to answer a quick survey that I'm doing regarding kit car owners perception towards the carbon fibre tub. It will take less than 2 minutes to answer and your responses will be stored anonymously. The link is below:

https://goo.gl/forms/qC9vRV5eGaoh20G33

Cheers,

7Fan7


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PostPosted: March 28, 2017, 8:45 am 
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Sam_68 wrote:
7Fan7 wrote:
It would be great if you could spare 2 minutes to answer this survey, which I'm conducting as part of a university project.

Done.

But I'm hardly your target demographic: I design them, these days, rather than buy them.


Thanks for the response! Hadn't realised you already answered the survey, when I posted the previous reply regarding the photobucket picture.

Cheers,

7Fan7


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PostPosted: March 28, 2017, 10:12 am 
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7Fan7 wrote:
...the stiffness of the chassis has increased about 30%, 40kg weight saving was inclusive of the rotary engine but if you're looking at the chassis only, it's about 10% weight saving.


I think they will need to be a lot more radical in their thinking if they are intending to actually sell any of the Wankel engined cars, in that case. The price the AIE were quoting me for the engine was ludicrous, and would make it a very expensive car (especially for one with only 120bhp). I'd be looking for a lot more than a 30% increase in stiffness over the Westfield spaceframe (which has pretty poor baseline stiffness) and a 40kg weight saving, if I was spending that sort of money.

You could get a 40kg weight saving from the tub alone (along with a much more substantial increase in stiffness), if you went to a full carbon monocoque instead of using steel subframes... as was demonstrated by the FW400. Which would mean you could forget about the expensive, specialised and unreliable Wankel engine and just use a standard drivetrain.

They should be looking at 'productionising' a cheaper, simpler version of the FW400 tub instead of fannying around with fancy engines in a mongrel, hybrid chassis.


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PostPosted: March 30, 2017, 11:52 am 
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Putting myself in the picture (literally) while working on the gas tank placement. I'm considering a 12" wide tank(s) in the side pods ala GT40 or a slim and tall 7"x30x17 size tank tucked in behind the passenger compartment across the rear firewall, in front of the engine. Honestly the 1st option is a bit scary if I were to get T-boned. Anyone have experience with either of these set ups I'm all ears for advice. A swirl tank is also planned. Thanks for looking. -Vinny


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PostPosted: April 3, 2017, 1:35 pm 
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Adding more structure around the cabin, side pontoons and front scuttle, also the forward section that will be the nose support area. Opinions greatly appreciated, Cheers, Vinny


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Chassis Balsa Apr2017.jpg
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Chassis Balsa2 Apr2017.jpg
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PostPosted: April 3, 2017, 1:51 pm 
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For the next structure(s) I plan to add I will likely make the cross-members over the engine and transmission removable as a bolt-in affair. The front upper scuttle area also needs addition reinforcement (see yellow bars) I'm attempted to keep these bars from inflicting injury to the passenger compartment. And the more triangle bracing at the nose support radiator area. Thanks for looking Cheers -Vinny


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PostPosted: April 4, 2017, 2:21 pm 
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You have too much stuff there now. You need to fight your way to something a bit simpler, it will make you happier I think.

Just some suggestions, but starting at the front you don't need three layers of tubes. I'm not sure what the upper layer is, but I think you can move the "W" I suggested back down - there it lines up with what you are doing for the side pods. The radiator support is already extremely strong vertically, it can perhaps use a very light diagonal brace at the bottom. If you need foot room try to raise that area of frame a couple of inches.

Maybe your fighting to make sure you have ingress/egress from the car with bodywork? I'm not sure what you are picturing for doors. The little jog in the upper rail where it joins the rear tubing by the driver's shoulder needs to line up. Maybe your seat is too thick and the driver needs to be 2" lower? I don't think there is a real comfort issue there a good bucket seat offers a lot of support.

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PostPosted: April 4, 2017, 4:04 pm 
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Also consider that you might be sheeting some of those sections, e.g. the floor, which should allow you to eliminate a few of those diagonals. I think a lot of frame designers tend to rely entirely on tubes.


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PostPosted: April 4, 2017, 6:25 pm 
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Just some suggestions, but starting at the front you don't need three layers of tubes. I'm not sure what the upper layer is, but I think you can move the "W" I suggested back down - there it lines up with what you are doing for the side pods. When the 'W' was low it fouled the footbox/pedal area so I attempted to move it up.

The radiator support is already extremely strong vertically, it can perhaps use a very light diagonal brace at the bottom. If you need foot room try to raise that area of frame a couple of inches. Yes, The model does not clearly show the 2 sizes of tube in the design, which are 1.5'' x 1.5'' for the main structure and 1'' x 1'' for secondary braces. Earlier in this thread a Toronado (GT40) frame picture was posted, it uses 3 layers of tube up front and serves as the upper supports for the body work.
Maybe your fighting to make sure you have ingress/egress from the car with bodywork? I'm not sure what you are picturing for doors. This is a full body car with 12'' sills and gullwing doors, I attached an image here.

The little jog in the upper rail where it joins the rear tubing by the driver's shoulder needs to line up. I've been scratching my head to have that area be more fluid. The original car has a monocouqe and a bolt on upper roll hoop that makes the A and B pillars.

Maybe your seat is too thick and the driver needs to be 2" lower? I don't think there is a real comfort issue there a good bucket seat offers a lot of support. A new model of 'Me' is in order, I think the current Me is to tall.
.
Also consider that you might be sheeting some of those sections, e.g. the floor, which should allow you to eliminate a few of those diagonals. I think a lot of frame designers tend to rely entirely on tubes. I plan to sheet the cabin, cowl and firewall in aluminum and steel.
.
Thank you for taking the time to assist me, Its greatly appreciated. -Vinny


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Mercedes-Benz-CLK-GTR-Coupe2.jpg
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chassis tornado4.jpg
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PostPosted: April 5, 2017, 3:09 pm 
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Let's try to look at a simpler example and then figure out how to apply those ideas to what you are trying to do. When your struggling with something complex, and a 3D car frame can certainly be complex, try to find some simple ways to see it.

Given you want:
- 12" sill for entering and exiting the car
- more than 12" in the front and rear for practical space reasons
- one main structure for the car with possible sub structures to hang things off

I think the last point is important for practical reasons like being able to understand and build your structure. Imagine a truss you design that would lay flat on your build table. It could be like the side of a cantilever bridge. Cantilever bridges are ones built of trusses with no suspending cables. They are often taller near their supports but taper down, sometimes to a long section of constant height. This is what you are looking for.

Then you take this idea and change it to be more 3D by making it narrower in the front area for example. This truss is the side of the car and you now stand it up on it's edge and make it kink inwards for the front area. This bend is done where you put one of those "W" brace area across the car and it's high enough now to not be in your way.

Here is a quick picture maybe it explains what I am trying to say. You would add more to make the pontoon, I can draw more later if it helps. You do the height change the same way in the rear to match your needs.


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Truss.jpg
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PostPosted: April 7, 2017, 6:06 pm 
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Thanks Marcus for taking the time to reply, I've been looking at the drawing you posted and comparing it to my model. I think model #1 is going to turn into a model #2 incorporating your suggestions and including the fuel tank, radiator and revised seat with driver.


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PostPosted: April 9, 2017, 3:12 am 
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Missed your reply. I'll put a few more tubes in to get to the radiator and fill out the sidepod a bit...

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Car9 Roadster information - models, drawings, resources etc.


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PostPosted: April 11, 2017, 6:49 am 
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I would greatly appreciate that. Cheers, Vinny


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PostPosted: April 13, 2017, 3:03 pm 
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I made some progress. I started a drawing for you in an old drawing I had for a Car9 midi with a Subaru engine. Pretty quickly it became easier to just put some changes in that drawing for you because it had more stuff attached to it. When you do a SketchUp drawing you can put items in different "layers" which you can turn on and off, that's great for comparing things, allowing for options and not having to redraw everything.

I also went and looked up the Tornado kit car which turns out to be a UK replica of a GT40. I've attached another picture of it with the wheels on it from a different angle. I think you can see here that it seems mostly to be a short frame about 12" tall and the other stuff is to support the body and some other details. It explains a bit the shape of those extra parts.

In the picture of my model below there is trouble in the area around the front wheel wells. The "W" brace above the drivers feet needs to shorten up like your model with the seated driver above, and your model needs to raise the part with the "W" brace by doing something like I did on the side. I'll do a little more to do those things.

You might want to learn some SketchUp. Not knocking real models - its a lot of work either way. Partly I do the SketchUp so other people can benefit from my work. Some of the parts in that model were contributed by other people.


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Car9_Midi_early1.jpg [ 188.81 KiB | Viewed 721 times ]

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