LocostUSA.com

Hello forum,

I have been reading this forum for a great many months; it has been a great resource to me.

I am designing/ building a single seater, 2f1r "reverse" trike. It is "F1 inspired," utilizing a "recumbent" seating style, with total height < 36in.

I will be using an R1 as a donor, while fitting a larger back tire (planning on stealing the "boat anchor" and "jacktube" idea from Wyked's three wheeler)

I will spare you any more details until the build diary; i just aquired a shop, and am outfitting it presently. I am hoping to commence building within the end of the month.



ANYWAYS!

Here is my lingering concern:

I have designed a suspension which, frankly, is very similar to (with the exception of longer a arms) the locost front end, with some adjustments made to compensate for the longer arms, and increased propensity to roll from the single back tire. But that's all being thrown on its ear because:

The rear roll center, -because it is a single tire, the rear RC is set static at ground level. However, as currently designed, my front roll center is a few inches ABOVE ground. - That being said, i have come to find out there are a few parameters i must stay within for best results, namely,

A. The front/rear RC axis should ideally slope downward when moving from back to front.
***see below
B. The RC for either front or rear should not be below ground.

***
However, i have read that there might be an exception to parameter A above, namely, that the relative height of the front and rear roll centers are not/should not be take in respect to ground level, but rather, in respect to the "mass centroid axis." wherein, the slope of the RC axis should = Slope of the mass centroid axis, which is the mean slope of the sectional COG points for the entire vehicle.

OK

so, if A,B are true, and rear RC is constant at Ground, then i am currently outside of my design parameters, with front RC > rear RC.

However, if this mass centroid axis thing is the case, then i am probably ok, insomuch as my design involves a "lifted" front nose, which will have a sectional COG @ aprox. 15" above ground, as opposed to the rear sectional COG which is likely closer to 12" above ground. -- if the front COG is 3-4 inches higher, my front RC can be too, or at least that's the reasoning....


Finally, if in fact i am outside the design parameters, and the mass centroid stuff is baloney, then, it seems my best bet is to set the front RC at 0" or ground level, by doing something that just feels wrong; making the a-arms parrallel. (i could, however still make them unequal length, right?)


A design of simillar charachter is the "scorpion P6" located Here : http://www.scorpionmotorsports.com/

-this seems to have parrallel a-arms, as does (if i'm not mistaken) the "indycycle", one of the first 2f1r "indy inspired" reverse trike.

HOWEVER, the t-rex seems to have unequal length, non-parrellel a-arms.

thoughts?

I have been working on my own 2f1r trike for a while now, but so far I have no performance numbers to share.

One thing I did was make the pivot of the front end on an axis through the contact point of the rear wheel and the ground. The whole car except the front end leans like a motorcycle.

The front axle is from an old (pre-'67) VW, which gives it pretty much parallel motion of the wheels in the vertical plane. The other advantage for my design is that the whole front-end unit was built by VW to revolve around a small central frame part, which was a fairly simple conversion to the pivoted type I had in mind.

So the shaft connecting the two parts, the front (glued to the ground) and the rear (which pivots like a motorcycle), is angled upward slightly, from the ground contact of the rear wheel to the bearing up front, which is about 10 inches off the ground. I am not too concerned about the high ground clearance here.

I know this doesn't answer your question, but I hope sharing helps.

If I am lucky, later this spring or summer I'll have some results and will be able to argue with more certainty.

I suggest you use the design you have. If your intention is to mass produce these, consider a mule prototype rather than attempting a finished product or a bolt on front subframe that can be swapped with other designs.

The idea that the front roll couple (roll center distance to cg) should be equal to the rear or slightly greater is for some under steer leaving a little more of the traction pie for a rwd platform, but this is based on the assumption of two rear wheels with a similar track that can be tuned for roll.

While sliding pillar morgan and vw beam appear crude next to modern suspension, the roll center height is equal to the rear. They are also more compact in width, allowing for a more forward cg for a given track width. The improved camber gain of the modern suspension is great, but it doesn’t make sense to build one end of a car with great capability to corner, only to detune it for an acceptable balance with a single rear wheel. It will be cool and interesting, but it won’t necessarily handle as well as vw or morgan based suspension (i.e. 3 wheeled drift). A truly high performance trike would be fwd with a forward cg (research the Trihawk from the ‘80s).

For more info on the trihawk, see Road and Track, May, 1982. Here is a more recent article:
http://ezinearticles.com/?When-Hawgs-Co ... &id=580240

It seems they were owned by Harley Davidson.

http://www.3wheelers.com/trihawk.html

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If you're saying what I think, you beat me to it; I've been tossing around the same idea.

I'm also trying to banish body roll, or better yet have it lean into turns.

It seems that this could be overdone though, as it could put excessive negative camber on the rear wheel and loss of traction.

For this to happen, the CG with driver needs to be on or below the roll axis; is it?

Could you share how you're going to implement the pivot?

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Noah

Use a VW beam with a thick anti roll bar on it to keep it all flat maximising rear contact patch.

The great thing about the beam is it deflects as much backwards as up so goes over bumps very smoothly indeed and that's a good thing on a trike as the wheels won't catch in holes as much as a double arm will.

So far, this is theory, untested. One of the problems with the theory is that it will take a lot of tries to get it to work properly. For starters, I will put together a simple 3-wheeler, with the stuff to make it perform as I want it to in place, more-or-less, but not functioning. The pivots will be locked at first in other words.

My first attempt will be to use hydraulics to do the job. This has the advantage that reverse can be included by incorporating a combination pump/motor (not too big) run off the driveshaft, and a tank to keep some fluid under pressure.

The hydraulics will be foremost used to activate a cylinder to move and hold, as the driver desires, the angle of pitch in turns. This is helped by a valve fixed to the seat, which itself is free to rotate (to a limited degree) sending pressure changes to the cylinder, left and right.

Then it will also be available to run the hydraulic motor, when the engine is disengaged, to go in reverse. About three HP I am assuming, and I think that is plenty, for as long as the tank has pressure.

There are a lot of details I don't have the space or the time to get detailed on tonight, but all the parts are on hand or on order. The specific valve to be used to control the cylinder is only a sketch and should be bought instead of made if it is available. I haven't seen it yet but I would assume something similar is out there.

The car is about fully designed; I have a cartoon pic of it done by my brother-in-law which I will add here. It is pretty good, but you have to observe the front end as a true VW part. Some artistic license had to be given.

Couldn't you do about the same thing by inclining the wishbones down at the back?

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Noah

The wheels don't care what mechanism you use to achieve the appropriate arc.

Thing is a Bug's front end is all one piece so just bolt or weld it on.

Gimme the 5cent summary of the VW beam? And how it moves *back*? I actually had to work on a ACVW once and I just saw dual parallel trailing arms. The only advantage of those is they loose grip as progressively (and greatly!) as a possible to prevent oversteer. Anyway, I'm somewhat disagreeing that the wheel moves back- two more or less horizontal & longitudinal trailing arms, longitudinal motion is nil around right height...??