Reverse Trike
 

If you were to build a reverse trike car with the engine in the front and front wheel drive, how would you handle the rear wheel? It needs to have a functioning hydraulic rear brake and a manual parking brake.

Here is what I've come up so far:
http://i1271.photobucket.com/albums/...s/swingarm.png

By using the rear wheel assembly from the donor car, I can be confident that the brakes and emergency brake will be easy to assemble and I won't run into any problems.

Look at youtube reverse trike alot are that way

groundflyer- How are you planning on handling your rear brakes? I would like to use a motorcycle frame because i would save time, I'm just not sure how the brakes would work out.

My bike frame is older with just a rear brake by foot so it will be a E brake
If you use a newer bike with hydrolic disk and just plug the car brake system and bike may need a different proportioning valve.

Maybe using a bike the same as or similar to yours is the way to go.

How do you think braking will be with only the front brakes?

It doesn't seem so complicated to set up the rear brake, would just need to block one of the rear brake lines at the master cylinder and remove one of the E-brake cables at its assembly...

so if I were to use car rear parts, how would I be sure that the rear end is strong enough?

"Strong enough" begs the question of how much strength is actually needed. Is your reverse trike going to be significantly lighter than the four-wheeler you are using the parts from? Presumably it is, but you would need to make certain.

If the rear wheel carries the same load as one of the two rear wheels of the four-wheel setup, then the stock parts (hub, bearing, etc.) should be quite strong enough. The swing-arm needs to be strong; the design you show could provide enough strength, but you will have to make it out of the right materials and brace it properly and so on. Lots of details that will make or break it.

For brakes, you will need to re-engineer the system to at least some extent. The car parts will be set up to push enough volume for two front brakes and two rear brakes. There will be two brake circuits, either one feeding the front and one the rear, or with each feeding a diagonal (LF/RR versus RF/LR). When there is only one rear brake, the volume that one circuit has to move will be significantly different. You also have to consider proportioning; if you have too much rear brake bias the rear will lock up first, which will tend to make the rear of the vehicle try to become the front of the vehicle.

So you will have to address the brake system pretty carefully and work through the volumes and pressures with some care.

Even if you put both rear brake calipers on the single wheel, you should get a lot more clamping force for a given pedal pressure on that one wheel than on two wheels. So you would want some sort of additional proportioning mechanism...

I know that there are racing parts that can be used to limit the brake line pressures going to at least one circuit; possibly there are ones that can work on two circuits (for the diagonally-linked brakes).

Unfortunately, it is not as simple as it looks at first. Plan on a good bit of testing...

-soD

That's particularly critical. Anyway, it might be not so hard to get some parts from a heavier vehicle. Considering a Civic as the base car, rear wheel hub and bearing out of an Accord can work. Another vehicle worth to take a look is the Volkswagen Transporter T4, which was more widely available in Canada and Mexico: it doesn't have a rear axle in the 2WD versions, it has 2 swing-arms instead.

Rear hub from a mid sized 90's GM, has caliper with cable lock attachment point on it. Just take the while rear spindle from a donor car.

If could get 3 of these calipers, wouldn't be so bad to make an all-mechanical brake assembly, without hydraulics and vacuum booster...

Not legal in most states in the US if it's to be registered as a car. Also, many states have laws (I imagine, haven't checked into it directly) against modifying existing brake systems as part of their inspection process to system-types not originally installed (subbing hydraulic for mechanical).

The idea would be to drop the MC size by 1/8th inch (unless moving from drum brakes in the rear) and add the rear fluid master cylinder, then hook a cable to lock it for an emergency brake.

However, in most states, 3 wheelers are registered (can be) as motorcycles and are therefore only subject to the motorcycle inspection procedure. Ergo, they don't actually need an emergency brake or parking brake system and needn't account for brake failure with redundancy systems, leaving him the opportunity to use whatever brake system works adequately for his purposes.

The GM suggestion was just that, and only because it affords a disc brake with hydraulic and mechanical capability, including the disk and a wheel hub with a fairly common 5-lug bolt pattern for which wheels can be sourced from literally 100's of vehicles spanning half a century or better.

Once you settle on those parts, the really interesting imagineering begins. You could do worse than start here:

Zero Cost Modelling of SpaceFrames

So I've been doing some design work and this is what I've come up with:
http://i1271.photobucket.com/albums/...etrodesign.gif
I wish I had some CAD education, but I guess that's what college will be for :confused:

On a side note, I've been researching Megasquirt standalone ECU's and I will definitely be building one for this car. It should allow for lean burn close to Honda lean burn levels.

I see now where your question is coming from. It looks like you're going back from four wheels to a tricycle.
http://i.imgur.com/gkI8h.jpg

Variable wheelbase is all the rage. MIT and Toyota do it.

Put a horizontal hinge, kind of like a motorcycle framehead, at the gray dot. The subframe would be a parallelogram 4-bar linkage with coil-over-shock[s], and a positive stop at the front and back.

I haven't thought out the telescoping bodywork yet.

I think making a 4 wheeled car into a trike would be a big problem -- the wheel geometry is just too unstable. If you want to make major modifications, go for a narrowed rear track; similar to what Dave Cloud did to a Metro to turn it into the Dolphin.

There are a lot of videos on youtube with a lot of reverse trikes and they seems pretty stable to me. The worst thing I can do is not try it. If things don't work out, it won't be too hard to cut the wheel off and put 2 in it's place. I'm sure it won't handle nearly as well and there will be rear traction problems, but there is nothing wrong with taking corners slowly.

the wheel geometry is just too unstable. How ? I already have a project reverse trike crx and that this is solid.. rolls with ease also.

What you don't want is a front wheel trike race

https://www.youtube.com/watch?v=KGULcLUr0I4

At the limit, a nose-heavy four wheel car wants to become a three-wheeler anyway.
http://i.imgur.com/mxP83.jpg

With 66/33 weight distribution and the suspension sorted out, the rear wheel should swing out and track behind the outside front wheel. A longer wheelbase helps, but creates problems parking, that why I suggested the variable wheelbase. I don't expect you to try it, it's just a thought experiment.

The biggest problem I see is the lower rear corner of the door window glass when it is rolled down into the door. That is the constraint on plan taper in the lower body.

variable wheel base is cool, but definitely beyond the scope of my project which is basically a $5000, 100 mpg car. I'm going to be looking for a metro and will be doing a project very similar to groundflyer's so hopefully anything he finds out will help me to learn. After all, that's what it's all about.

As I said I didn't expect you to change your plans. I just wanted to do the picture. I think the best application would be a pedal powered vehicle that would be like a recumbent trike when it's stretched out and a wheelchair when it's folded up.

I found 'CRX HF reverse trike project'. That's an interesting project. I don't know how I missed the thread, I try to keep an eye on Ecomodding Central. I especially like the 'Zoleco'. I also see useful discussion on the underbody

So here's a trike:
http://i.imgur.com/1fyXs.jpg
It's from Concept cars and trucks: Railbike vehicle model by Chris Binnett

Hey Neil,

I am going to have to disagree with this statement. 4 wheeled vehicles that are made out of a unibody chassis are difficult to convert and can be dangerous however 4 wheeled vehicles that have backbone chassis are very safe and easy to convert into a reverse trike.

As far as wheel geometry being to unstable that can not be more untrue. 3 wheelers with the single rear wheel design can be extremely stable even better in some cases than 4 wheelers if properly designed. A triangular shape is extremely strong and stable geometrically. Keep the center of gravity low and the weight bias toward the front of the reverse trike and you have the recipe for a very stable sports car handling vehicle.

I would not go with a narrowed rear track for many reasons. Some of those reasons include some of our basic principles of ecomodding.

#1. Less mass = better acceleration Newtons 2nd law overal weight can be greatly reduced eliminating one tire, wheel, brake, and suspension assembly can reduce curb weight dramatically. Frame weight can also be reduced the body can be lighter also due to more of a triangular shape rather than a rectangular shape. The engine can be lighter also do to the less mass. Add all that weight elimination and you have a car that weighs much less than the dolphins 3000# curb weight.

#2. Rolling resistance is reduced by 25% roughly with one less wheel! Again vehicle weight will also reduce rolling resistance. Narrower tires can also be utilized to even further reduce rolling resistance.

#3. Aerodynamic drag is reduced by the 3 wheelers natural teardrop shape. The Dolphin despite having 4 wheels did do a good job of reducing aerodynamic drag!

#4. Lower polar moment of inertia is also possible.

A 3 wheeled version of the Dolphin could be made much lighter out of a 4 wheeled car. It would also have better range and performance if carefully designed.

GreenHornet :-)

Please read the Riley page on 3 wheel dynamics that the OP linked to. (I first saw that page about 6 years ago.) The Cg is absolutely critical on a 3 wheel design - if it is too far back and/or too high up for all driving conditions, then they will be unstable.

As you mention in point #3, a reverse trike has the potential to greatly improve the aerodynamics, with the sides tapering in - which by the way would also improve the Cg as well as the Cd. But, a 4 wheeled design can also have a narrowing taper (see Dave Cloud's Dolphin) but avoid the stability challenge.

The Dolphin does weigh a lot - it carrying a ton (almost literally) of lead acid batteries and the structure to support it. But if you put a lithium pack in it with the same capacity, it would weigh about 1,500 less. The Dolphin chassis without the batteries is about 1,200 pounds, which is probably similar to the CR-X trike in this thread with it's engine in place.

The Dolphin is also one of the lowest aerodynamic drag cars I know of. It is also one of the most efficient cars that I know of; despite it's weight. If you build a trike, but do not take full advantage of the format, and/or you don't avoid the pitfalls of the layout, then why do it?

So by eliminating a wheel, reducing the weight of the vehicle, and using narrower tires rolling resistance would increase then by 25% roughly :-)

ok

Neil I am not bashing on the Dolphin in fact I think it was a great build albeit the cost figures were flawed a bit however I do agree with you on the aerodynamics of it as I stated in the first post. Yes also its a lead sled agreed, If Lithium was used weight would be reduced dramatically.

My original point was by going with 3 wheels you can have further weight reduction, Better natural Aero capability, reduced rolling resistance, and lower polar moment of inertia. There is no real big advantage to having the 4th wheel as I see it other than to have a bigger vehicle with more space for cargo.

There are plenty of 3 wheeled reverse trikes that do not take full advantage of the design. Many are designed as having high speed performance and sports car handling such as the T-Rex and its derivatives. They have wide front tracks and narrow wheelbases with low centers of gravity. This makes them extremely stable and quick in and out of turns.

There are not very many that I have seen that are even fully enclosed it is a shame. Zap Alias and Myers Motors to name a few has fully enclosed models which they are taking orders for now. I agree with you I would not do it unless I was taking full advantage of the 3 wheel design potential.

GreenHornet

The weight of the vehicle is the only thing that matters for the rolling resistance (if the tires are the same) - it doesn't matter whether it has 2 wheels, or 3 or 4. The weight is divided by the number of wheels, and the rolling resistance total is still the same, if the weight is the same.

Narrower wheels only necessarily affects the aerodynamics. In other words, a narrower tire is not inherently lower rolling resistance.

Trikes can be well done or poorly done - that goes without saying. The point is whether only reducing weight, but not improving aero drag is worth it - if you also sacrifice stability.

I'll point to Allert Jacob's streamliner motorcycle. It now weighs 231 pounds - about 80 pounds more than stock; which is a 34% increase! But, along with taller gearing, the drastically reduced aero drag more than doubled the FE.

Also, the efficiency of the drive train is huge factor. The Edison2 VLC X-Prize car got 102MPGe with an ICE in a 830 pound car. But the eVLC gets 245MPGe with an electric motor despite weighing 1,140 pounds; which is a 37% increase.

Somehow I doubt that the motorcycle engine is as efficient as the original CR-X engine was.

My hypothesis is that drivetrain efficiency is the most important factor, followed by aerodynamic drag, followed by weight, and the fourth most important factor is overall rolling resistance.

Neil,

I would agree 3 wheelers can be well done or poorly done but that goes for 4 wheeled cars also as we have plenty of them on the road these days to prove it! You seem to think 3 wheelers have inherent compromised stability. I would agree with this in the respect of a front wheeled 3 wheeler but not so for a single rear wheel. I still disagree on the rolling resistance point but we can agree to disagree.

So we are not that much different in our views really I just place priority a little different but we have the same components.

For me it would look like this:

#1. Total vehicle weight
#2. Aero
#3. Rolling resistance
#4. Drivetrain Efficiency

All of these components matter but weight effects it the most in my opinion. Once you have completed your build its hard to take weight off. So its better to design for weight reduction from the very start. Aero can be tweaked with a finished vehicle but why not incorporate it from the get go.

Good points though Neil I am enjoying our discussion,

GreenHornet :-)

FASCINATING! 3 years ago I had practically given up the Myers Duo was going anywhere, and thought it failed. That is terrific news to me that they continued! 3 years worth of an open Chinese electric scooter is just about enough for me - I have 2 new four-letter words: cold wind. Thanks GreenHornet!

A very good example of a 4 wheeled car that is designed for low weight, great aerodynamics, drivetrain efficiency, and might I say has a reduced rear track is the VW L1 series of cars. In fact these are my absolute favorite 4 wheeled cars its to bad we will not see them on the roads anytime soon here in the states. Even if they did manage to get them here I don't think I would want to see the price tag LOL!

So in the meantime we just do our own versions like the Dolphin, XR3, Vortex and etc.. :-)

No matter if its with a 4 wheeled car with a reduced rear track or a 3 wheeled version it would be a step in the right direction.

GreenHornet!

All this activity and no-one commented on the presumed (in)stability of the Railbike.

How are you delimiting that? Currently in production?

Here's the classic example of the 'fully enclosed' trike. It's even made out of a 4-wheeler. I grabbed these out of a long boring talk by Sir Norman Foster, he's the owner of the 4th Dymaxion.
http://i.imgur.com/5jTnVud.png
http://i.imgur.com/MoXfDPZ.png

And here is Bucky's 4th Dymaxion, never built:
http://i.imgur.com/ShGlDLm.png
The drawing I had seen before was a six wheel trike, with in-hub motors. And a variable wheelbase. This one has 3 radial engines, mounted fairly high up. It reminds me of the Electric Egg which admittedly is not 'fully enclosed'.
http://i.imgur.com/RNzps.jpg

Frank Lee -- The next time you want to change your profile pic, I recommend you crop this:
http://i.imgur.com/Q8zNOwU.jpg

It has that happy, happy, joy, joy thing going.

Awesome pic! :thumbup:

if I was building a reverse trike today
 

I would start with Piaggios MP3 500, 400 0r 250 cc easy to purchase 3 to 5,000 used, all the parts are there. I would extend the frame a little if I wanted more room and recumbant seating to lower overall shell, one seat behind the other and design an enclosed aerodynamic shell. I would be starting off with something that already does 70mpg has an amazing front suspension. The only issue to solve would be the front bearings or be prepared to change them often. I think that a modified version of the mp3 is the way of futur commuting, in an EV, fully enclosed model two seater one behind the other with all the safety features like airbags, roll cage along the lines of BMWs C1, I am not sure how it would handle in the snow/ice being so light. I am not sure how any very light vehicle would handle snow/ice?? I guess that would be another issue to solve.