How to Design Suspension Geometry for a Front Wheel Driven Trike?

[wolram]

A front wheel driven trike to be exact, how would i start designing
the suspension geometry, i have in mind an ultra light vehicle
driven by the most economical engine "within reason", and street
legal, maximum speed 70 mph, to carry two persons with some
comfort. the driven wheels would be at front of the vehicle.

 

[brewnog]

I assume then that your single wheel would be trailing?

Designs which spring to mind are the Messerschmitt bubble car and the Morgan three-wheeler, both are outdated (and the Morgan was rear wheel drive) but fit the bill of lightweight, two seater, three-wheelers, perhaps you want to do some research?

 

[wolram]

Brewnog
yes i do need to do some research, i though i would start with wheel geometry
and suspension, i want to keep on the lines of a morgan, but with modern
parts.But what is the best way to research 3 wheeler wheel geometry?

 

[brewnog]

I reckon it would be pretty hard to start from scratch (especially trying to prove to the SVA man that your own steering and suspension designs were safe), but there are plenty of kits around for this kind of thing. I met a guy who was building one based on a Citroen 2CV, but it looked amazing! I think it was probably a Pembleton (http://www.pembleton.co.uk), it wouldn't be too hard to incorporate more modern components.

 

[LunchBox]

You may want to check local laws...

Three wheelers of ANY kind are not street legal in some US states (which I found out by being pulled over on a back road).

Cheers...

 

[brewnog]

Three wheelers are relatively common here, just because it's got three wheels won't exempt him from being able to get street-legal status. However, he will need to take and pass a single vehicle approval (SVA) test, which covers things like weld quality, curvature radii on exterior fittings, light positioning etc.

 

[wolram]

brewnog
i want to build something that is practical and economical for short trips
ie, to the supermarket, it will not have to have stunning performance, but
must have good economy, and a 70 mph maximum speed, the reason
for three wheels is taxation .

 

[brewnog]

Well are you intent on building it from scratch? Most of the kits allow pretty cheap building of some really lightweight (and hence 50mpg upwards is usual) vehicles, and obviously you can tailor them to suit your needs. Building a car from scratch involves a lot of hard work, and is much harder than it was, say, ten years ago before the mandatory SVA test.

 

[polyb]

wolram,

I have a brother-in-law that does this with a friend of his and I have had the pleasure of playing with one of these beasts. A lot of trikes are built using old VW bugs that are chopped up and rigged to be a trike. So you may want to look into that, of course you can use just about any vehicle that has the engine in the rear. These toys can be quite elaborate and really cool!

Have a look at this site:

http://btw-trikers.org/uploads/home.php

They have a forum and may be able to help you out! Plus a lot of other goodies like photos, links, etc. When my bro-in-law was showing of the stuff they had built he showed me the site.

 

[wolram]

Thats a great site Polyb, lots of photos and info, but my three
wheeler is going to have the two wheels at the front, i have found
loads of info on the web, should keep me busy for a while, thanks
all for advice.

 

[ohwilleke]

Motorcycles with a sidecar are quite fuel efficient, and while not exactly in your mandate, have the virtue of greatly reducing insurance costs because the historical records is that motorcycles with sidecars are in fewer accidents than four wheel cars. In contrast, three wheel trikes have a very bad historical accident record (because reckless people tend to drive them) and thus might have very high insurance costs.

 

[wolram]

Ohwilleke
Me reckless, perish the thought.
70 mph is my max from now on, and as i hate to give
government my hard earned sterling frugality is the priority.

 

[Cliff_J]

Here's a little more info for you that you may not have run across yet:
http://www.rqriley.com/3-wheel.htm

Kinda funny looking but the Tri-Magnum plans they sell is all about taking an old motorcycle and using it as the back third wheel with the passenger comparment supported by the front two wheels.

The thing I never cared for on my 3 wheeled ATV (Yamaha 250 Tri-Z) was that the one small front tire didn't have enough traction to turn on slippery surfaces, was too light and wheelied a lot, and didn't have enough floatation on very soft surfaces. A Yamaha 350 Banshee 4 wheeled ATV fixes all those problems...

 

[mewmew]

When I was down in San Francisco we rented these crazy two person go carts that had two front wheels and one back wheel. It had to have "training" wheels because everytime you turned semi fast of course it would try and tip. It was fun to mess around in but I certainly wouldn't want one on a long term basis. I think the main problem is the fact its just plain dangerous to drive around something as small as a go-cart.

 

[danscope]

A front wheel driven trike to be exact, how would i start designing
the suspension geometry, i have in mind an ultra light vehicle
driven by the most economical engine "within reason", and street
legal, maximum speed 70 mph, to carry two persons with some
comfort. the driven wheels would be at front of the vehicle.

Hi, May I suggest that you employ a two wheels forward and a single wheel aft
configuration. The Major problem with single up front is that in a braking turn,
this design tends to dump the vehicle over quite easily. Where as the two wheels forward is quite stable. The three wheeled Morgan is a spactacular
performer in this regard. Read up.
Try www.3wheelers.com and look for the ones with two wheels forward.
These are the superior designs.
Also, there is recent development in what is called a "Leaning Trike". Give this a google and you shall see some remarkable designs, in that the bady leans toward the inside of the turn, making a most stable vehicle indeed.
The trick is in the driven wheels..or wheel.
These are interesting sites to visit. Press on,Sir.
Dan

 

[Danger]

Wouldn't do you much good in England, but in Canada there's another serious advantage to the 2 in front and 1 behind wheel system. In winter, you can replace the front wheels with skis and put a honking studded mud tire on the back.

 

[danscope]

Hi, You can always put two skis up front and a big balloon stud tire in back.
Than you can say"G'day!" . :)
It's all about the weight, and power required.
Dan

 

[Danger]

I still prefer the mud jobs, because our situation changes constantly. There is a saying here that if you don't like the weather, wait a minute. Balloon tires are a bit too special-purpose, whereas the Trailblazers on my Camino are good on a clear highway as well as climbing out of mudbogs. It's a lot easier to carry a couple of spare 'cycle tires to swap in for the skis than it is to also carry a spare rear wheel assembly.

 

[AlephZero]

brewnog
i want to build something that is practical and economical for short trips
ie, to the supermarket, it will not have to have stunning performance, but
must have good economy, and a 70 mph maximum speed, the reason
for three wheels is taxation .

See http://www.mp3.piaggio.com/

Does 3 wheels, 78 mph and 70 mpg meet your spec?

 

[danscope]

Hi, Interesting configuration. If I could spread the front wheels by a foot, and get a single nose wheel leg through the middle, I'd have something I could fly with. I'll have to find one that I can look at up close.
Thanks for the link.
Dan

 

[Panda]

These are relatively easy to build if you have access to a decent workshop and a well stocked scrap yard.

Number 1 you can get all the regulations from the DVLA. Make sure you get the ones for kit cars and single varient vehicles.

Number 2 Parts.
Power unit a good big V-Twin out of a wrecked bike. You don't need any frame so doesn't matter how mangled it is.

The front end from a small front wheel drive with strut suspension. This needs to be straight so look for a rear end right off. You don't need the engine.

A lot of square section tubing.

The only two difficult bits are...
1. making sure that your chassis picks up all suspension mounts properly from the car front end. Otherwise the ride will be all over the place.
2. Joining the V-Twin to the Car drive shafts. You need to fashion a drive box to get the chain drive out on both sides of the gearbox.

Chassis design needs careful thought but so long as it is stiff it will pass certification. generally if it looks right it will be stiff.

Make sure that you have good metal in your chassis for seat and seatbelt mounts. Assuming you are lifting these out of another car make sure the mounts are in the same orientation, and then buy new belts from a reputable supplier.

The best way to build is to get the major components and then see how they fit together. It takes longer but there is less complex calculation.

When you go to get your engineers certificate get to know the inspectors. A good inspector will tell you where things need attention and how to get through.

 

[danscope]

Hi Panda, Thanks for the tips. I have a BMW engine out of a Messerscmitt
(isetta) . Would like to build a Morgan 3 wheeler out of it and Be able to register it. That's asking a lot. Your tips will be welcomed. Are you using 1/8 th inch stock or heavier? What about reverse gear? (tricky...that..). Was thinking about a shaft drive to the rear...and perhaps an MGB transmission.
Nothing is easy. I have a pretty good shop...Miller stick welder, oxy/acet.
Do you recommend any front suspensions ( subaru..?).
Dan

 

[brewnog]

Front suspension for a Morgan-style 3 wheeler, I don't think you'll find better than the Citroen 2CV. In fact, that's an excellent donor for much of such a project.

 

[danscope]

Hi Brewnog, Thank you so much for that tip. Ah...now to the bone yard.
Press on!
Dan