I've got an idea for a low cost trike, using all the parts from a small fwd vehicle such as a Toyota starlet. It would use everything from the donor ,lights/seats/shocks/brakes/macpherson struts/steering rack/lower wishbones etc, so I wouldnt have to buy much stuff. A ladder chassis should be adequate for a trike and as it will be Fwd it wont be my 'optimum' vehicle so I shouldnt get Analysis Paralysis very much. Good practice for a real locost.
Some questions,
If I use oem shockssprings from a starlet whats going to happen to my ride? Will it be rock hard or bouncy as? The starlet weighs about 900kgs I think and if this trke is 400 kgs that would be less than half the weight. The donor shocks/springs would be a bit worn though, so it might not be so rock hard?

Does anyone know what a 1.3l 4efe engine weighs? I hope the trike wont tip onto its nose when I get out, as the engine is in front of the wheels. Maybe if I got a really big battery and mounted it at the back.

Keep working at it, I am just ordering a Pembleton kit right now, but have had a lot of thoughts on making a similar thing to what you're proposing (single car FWD hatch donor FWD trike)

Lengthen the wheelbase if you're worried about weight distribution.

do you have small cars like the british mini or small fiats where you are? I think they would be better donors for this kind of trike as they are very light and most likely to have sping and damper rates already correct for the trikes weight. You need a lot more support for the front struts than shown on your drawing.

Jap cars are most common over here, I guess I could use a daihatsu mira or similar but a starlets/corollas are a lot easier to find, esp crashed one in good condition.
If I put a strut brace across the top and some diagonal braces/gussets would that be good enough?
I was also thinking of a triangulated chassis like a TVR but this will be simpler and easier to make, less welds to inspect etc.

have you considered doing something like this? would be an easy way to make a destinctive trike style car







here's another thing you might consider, fancy one myself tbh just wish I had the time...

linky

forum linky






[Edited on 16/4/11 by Mr Whippy]

That tri magnum is awesome, but a looks like a lot of work.
I was thinking of something like this





Also lots of work but at least no compound curves I think. Should be able to make it out of aluminium or ply and glass.

that looks good, if i were doing this i would pick a donner where i can just remove the front subframe and then build the car around that. no need to design and build your own frame to do the same job.

also does the front wheels stick in a bit far? they look a bit to far in for the drivers legs considering they need to turn aswell. why not move them out a few inches and have wheel arches.

looks ok and would certainly stand out. The Tri-Magnum does look a lot of work but maybe not if you got hold of a very good sander like they use when glass skinning boat hulls. I do like it's building method, the idea of not having having to waste expensive GRP to just make a mould and that you also build in foam into the structure which will do a lot for crash protection.

My daft trike is a composite doodah with a few bits of metal hanging off it rather than metal with composite panels hanging off it..going for the anti social black lines off roundabouts streetfigher atitude rather than make a road racer......

Sounds interesting Triton, do you have any pictures/design concepts?

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Originally posted by Kwik
that looks good, if i were doing this i would pick a donner where i can just remove the front subframe and then build the car around that. no need to design and build your own frame to do the same job.

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how about a Smart diesel as a donor? they're about 700kg, RWD but could just move the whole setup to the front

A full size wood mockup, not completed yet. I think I might put a roof on it so I can drive in the rain, and with the recent price of petrol something aerodynamic would be good. Its just the doors/windows that will be a real mission to make. NZ LVVTA regs say doors must be able to withstand 11Kilonewtons force. I dont know wether they will apply to trikes though.

Its really fun making this chassis and feeling the stiffness build up with each triangulation. At first the whole thing was floppy as a jellyfish, then when the last diagonal went on (there's a diagonal across the windscreen representing the stiffness of the glass) it suddenly became ultra stiff. And its not even fully triangulated.

If the major strengthener in a chassis is the windscreen I suspect there could be a few issues!

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Originally posted by designer
If the major strengthener in a chassis is the windscreen I suspect there could be a few issues!

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The front screen is a structural part of most modern cars.

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nissan micra for a donor ?

im contemplating a trike build since , if your below 300kg , and can register it as a disabled vehicle , you pretty much miss out on iva , or even msva.

cvt volvos have a 90 degree transfer drive , so you could put a car engine onto a chain drive at the back .

lots of ideas floating round in my head .

A trike would have very little twisting loads anyway, I probably wont bother with making the roof structural. Also if I make the roof structural the insurance companies might say its a full roll cage and not want to insure it.

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Originally posted by designer

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The front screen is a structural part of most modern cars.

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Yes they are, and are bonded in as part of an overall chassis. Amateur build is a totally different matter, chassis rigidity must come from the chassis in our type of builds.

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I agree with Designer: where windscreens in production cars contribute to the overall stiffness, the structure will have been carefully calculated to ensure that they just contribute, without ever being sturcturally overloaded. And the prototypes will have then undergone many hundreds of thousainds of miles road testing to confirm that there are no problems.

If Rowlock's structure is, as he says, 'as floppy as a jellyfish' until he addes the bracing representing the stressed windscreen, it suggests that the windscreen would be taking a substantial amount of the loadings. Chances are, he could be building a car where the windscreen would crack every time he hit a decent sized bump or pothole.

Edited to add: Personally, I'd be looking at introducing a traingulated upper rail at elbow level along either side, so that the roof and windscreen don't need to be stressed.

[Edited on 28/8/11 by Sam_68]

Well isn't that a bit what this whole site is about. Doing something different, trying things out? A big manufacturer will also extensively test before they put a bigger more powerful engine in a production car. But on here it's normal to just tune or swap the engine, sometimes doubling the performance and just see how it goes...

Although yes I would say some additional strengthening would be good. Especially around the windscreen, supporting both the lower and upper corners of the screen frame. And maybe a horizontal brace across the sides to help counter bending forces, and go with half doors like most sevens. That might get you around the regulations for doors as well. But then again rowlocks says it isn't finished yet. And it's build from soft wood, presumably simply nailed together and not fitting all that well. Build it out of the right metal tubing, nicely fitting and welded properly and it would be a whole different ballgame.

And yes it would still be a risk to use a stressed windscreen.... but is any build on here risk free?

Being different and taking risks is one thing...

Deliberately designing a road vehicle where you know you're relying on a sheet of glass for a substantial part of your structural stiffness, without even attempting the calculations to prove it, doesn't sound like brave and radical engineering to me though: it sounds plain ill-conceived.

Well it might... But how many do you think calculated the specific strength of there own wishbone design? The rule of the game seems to be to just copy a design and adapt it to suit your own needs. At times even copying the faults the original designer made. And it might be me, but I think the risks on that are far bigger then that of a cracked windscreen.

But then again I'm not saying it will be fine, I'm saying it might work. I wouldn't be all to confident doing it on a car. But on a trike, with little twisting force in the chassis, it might work.

And like I said, with or without a stressed windscreen, it will need more (proper) triangulation. There are to many open polygons and unsupported corners to be useful for the strength of the chassis. But then again, aren't there quite a few trikes around with almost nothing more then your basic ladder chassis. Which seem to hold together fine.....

And yes... proof is nice. But as said so many times before... it's no use to calculate and analyse everything, unless you really know what you're doing.

If you've got the money to try it out, I'd say give it a go. Build a chassis you think might work with a stressed windscreen included (no need to get all the instruments, bodywork etc sorted, just the very basics) and give it a good thrashing in a field or something similar. See if it holds up, maybe you'll need to strengthen some areas. Or maybe you need to get back to the drawing board altogether.

Trial and error development might not be the fastest or the cheapest. But you'll learn a lot doing it, and gives practical real results. Instead of theoretical, with a large margin for error.

If you don't have the time or money to try something new... Then get yourself a proven ready build car, kit, or set of plans and follow them to the letter.

[Edited on 28/8/11 by JF]

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Originally posted by JFWell it might... But how many do you think calculated the specific strength of there own wishbone design?

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I do really see where you are coming from and I partially agree. No the windscreen shouldn't be holding the whole chassis together. But then again, preferably the integrity of the chassis shouldn't depend on any singular component if you ask me. Sometimes that's impossible (or atleast really hard) to avoid such as in suspension components. But almost every component on a car could cause mayor trouble if it gives way at the wrong moment. If you don't want that risk... you shouldn't drive a car... or a motorbike... or a bus... a train... an aircraft...

And well I can't help but laugh a bit about your commend about trial and error potentially getting you killed. Just about every single action in your life could potentially get you killed... Albeit that some things have a bigger risk then others. And I really do think that for the average amateur builder trying to calculate the strength of there vehicle is a greater risk then taking an estimated guess and seeing how it works out.

Even the big multinationals get it wrong once in a while. Even in critical parts of aircraft...

My point is... I don't see the problem in using a stressed windscreen for additional stiffness. Although the chassis should be able to hold itself together without the glass there.

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Originally posted by JF...almost every component on a car could cause mayor trouble if it gives way at the wrong moment. If you don't want that risk... you shouldn't drive a car... or a motorbike... or a bus... a train... an aircraft...

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My point is... I don't see the problem in using a stressed windscreen for additional stiffness. Although the chassis should be able to hold itself together without the glass there.

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Yeah a slight increase in stiffness is all I would be after. The only reason it was really floppy at first is because the joints werent very well made. And the main chassis rails were the same size as all the other pieces (I had lots of firewood that size). In a real ladder chassis the main rails would be significantly bigger, to be able to take twisting and bending loads.

Making stuff out of wood first is good I think because its weaker and you can twist it and feel which joints get stressed and feel where the triangulation needs to go. If you build it out of steel first, its so strong that you might not be able to tell that a joint is more stressed in comparison with other joints.

Actually it might be difficult to distribute the loads around the edge of the glass in the same way as a monocoque chassis can, even if you cut out the surround. Point loads might not be good for glass, lol.

[Edited on 29/8/11 by rowlocks]

Jeez Sam lighten up a little. I never said that you should just throw some bits and bobs together and take it for a spin on the public road.

And yes manufacturers use safety factors, and yes I know what they are, but my point was that even though they do use a safety factor there are still problems once in a while. When you really know what you do calculations can help a lot in design. It's when you don't know how to do the calculations and try anyway that the big failures happen. Because the outcome might indicate you can do with a lot less then you actually need. That's why I don't really advise going the calculus route for the amateur home builder.

I really do think it's saver to go by your gut feel and try it out in a stretch of farmland or something similar. You might find some weak spots, it might break, it might be fine. If it does seem sound and you go on to make it road worthy, get msva etc. Then still I'd check the whole chassis over on a regular basis. And I'd paint it a light colour that shows cracks at an early stage.

And I do believe that IVA is a good thing. And yes they may be over enthusiastic, and going over the top on some bits. And yes it's a shame it costs so much. But it's good for every home builder to have somebody else give your car a look over. If you've worked on it for so long you'll miss many (critical) safety concerns. But IVA doesn't catch everything. I could build a chassis completely by the locost book. But use far thinner walled box section. The IVA inspector wouldn't know. But it might fall apart on the very first speed bump. Hence the Aussies demand a stress test. Might be a hassle, but again I think it's a good thing.

And please dear Sam, I'm not stupid, and when I do get round to building my own design. It will probably be over engineered, and end up weighing more because I prefer it on the safe side and won't calculate if I can make that tube a little thinner. But I'd design it using common sense.

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Originally posted by JF

And please dear Sam, I'm not stupid, and when I do get round to building my own design. It will probably be over engineered, and end up weighing more because I prefer it on the safe side and won't calculate if I can make that tube a little thinner. But I'd design it using common sense.

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