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Author: Subject: Fwd Trike
rowlocks

posted on 15/4/11 at 10:37 PM Reply With Quote
Fwd Trike


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 shocks\springs 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.

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PSpirine

posted on 15/4/11 at 11:01 PM Reply With Quote
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.

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Mr Whippy

posted on 15/4/11 at 11:23 PM Reply With Quote
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.






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rowlocks

posted on 16/4/11 at 12:44 AM Reply With Quote
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.

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Mr Whippy

posted on 16/4/11 at 09:58 AM Reply With Quote
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]






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rowlocks

posted on 18/4/11 at 09:41 AM Reply With Quote
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.

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Kwik

posted on 18/4/11 at 11:04 AM Reply With Quote
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.

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Mr Whippy

posted on 18/4/11 at 11:32 AM Reply With Quote
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.






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Triton

posted on 23/4/11 at 09:58 AM Reply With Quote
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......





My Daughter has taken over production of the damn fine Triton race seats and her contact email is emmatrs@live.co.uk.

www.tritonraceseats.com

www.hairyhedgehog.com

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rowlocks

posted on 5/5/11 at 11:27 AM Reply With Quote
Sounds interesting Triton, do you have any pictures/design concepts?





quote:
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.



A subframe would be easier but could you recommend a suitable donor? Are there any light Fwd cars with subframes?

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Benzine

posted on 5/5/11 at 04:37 PM Reply With Quote
how about a Smart diesel as a donor? they're about 700kg, RWD but could just move the whole setup to the front
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rowlocks

posted on 27/8/11 at 02:07 AM Reply With Quote




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.

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designer

posted on 27/8/11 at 07:02 AM Reply With Quote
If the major strengthener in a chassis is the windscreen I suspect there could be a few issues!
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Mark Allanson

posted on 27/8/11 at 08:24 AM Reply With Quote
quote:
Originally posted by designer
If the major strengthener in a chassis is the windscreen I suspect there could be a few issues!


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





If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation

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designer

posted on 27/8/11 at 08:46 AM Reply With Quote
quote:

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



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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Volvorsport

posted on 27/8/11 at 09:51 AM Reply With Quote
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 .





www.dbsmotorsport.co.uk
getting dirty under a bus

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rowlocks

posted on 27/8/11 at 10:03 AM Reply With Quote
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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JF

posted on 27/8/11 at 11:56 AM Reply With Quote
quote:
Originally posted by designer
quote:

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



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.


And why is that? If you put some care in designing the surrounding structure you could simply cut the whole windscreen frame (including the glass itself) from your donor. And implement it in your chassis.

You'll just need to find a donor with the right shape and size windscreen and frame. Additional advantage is you'll have a oem screen. Easy to get replaced and nicely curved. Looks much neater and will help with aero.

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Sam_68

posted on 28/8/11 at 07:40 AM Reply With Quote
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]

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JF

posted on 28/8/11 at 11:40 AM Reply With Quote
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?

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Sam_68

posted on 28/8/11 at 12:20 PM Reply With Quote
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.

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JF

posted on 28/8/11 at 02:30 PM Reply With Quote
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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Sam_68

posted on 28/8/11 at 02:59 PM Reply With Quote
quote:
Originally posted by JFWell it might... But how many do you think calculated the specific strength of there own wishbone design?


I know that where people have, the thickness of tubing used is well below that typically seen (for instance Frank Costin's designs - a qualified aircraft engineer - were very slender indeed), so it's safe to say that the average 'Locost' wishbone design is heavily over-engineered.

Trial and error development certainly might not be the cheapest and it can potentially get you killed.

When it fails, glass doesn't exceed its elastic limit and bend a bit... it fractures very suddenly and irretrievably with a total loss of strangth. If that happens when you hit a bump mid-corner at speed and you're relying on it for a substantial part of your chassis stiffness, the consequences could be rather nasty.

I once had a suspension bolt fail in a Raffo Tipo 12 kit car whilst travelling at speed in a straight line (I became airborne over the crest of a hump in the road and the bolt sheared when I landed).

It's not something I wish to repeat.

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JF

posted on 28/8/11 at 09:00 PM Reply With Quote
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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Sam_68

posted on 28/8/11 at 09:26 PM Reply With Quote
quote:
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...


If it's safety-critical, you should engineer it to a sufficient safety factor (I assume you understand the concept of safety factors?) to ensure that its failure is highly unlikely. FWIIW, the majority of systems on aircraft (and brakes on cars, of course) are duplicated to make the likelihood of complete failure even less likely.

The point being that in all competently engineered and professionally designed forms of transport, professionally qualified stress engineers have assessed what is necessary, then multiplied that by a factor of 6 (or whatever) to reduce the chances of failure to an acceptable level.

I'm afraid that I find such a laissez faire attitude to safety on a vehicle to be used on public roads - where it's not just the builder at risk, but other road users - is highly irresponsible.

...and it's the sort of attitude that has seen us landed with SVA/IVA, and will doubtless see kit cars legislated off the road completely if we don't get our act together.

quote:
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.


It depends on your definition of 'using'. If it means that one of the happy consequences of fitting glass is a slight increase in torsional stiffness, that's fine. If it means that you are relying on the glass to make it work to a safe and proper extent - as seems to be the case with the OP's design - then I think you've got a big problem.

I think the chassis needs to be able to more than just 'hold itself together' without the glass; it needs to have enough beam strength and torsional stiffness to function properly under all circumstances without the glass there. And at present the OP's design doesn't seem to demonstrate this.

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