Reverse Trike

[freebeard]

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:

It's from Concept cars and trucks: Railbike vehicle model by Chris Binnett

[GreenHornet]

Originally Posted by NeilBlanchard

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.

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 :-)

[NeilBlanchard]

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?

[GreenHornet]

Originally Posted by Frank Lee

Sadly, this isn't the case.

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

ok

[GreenHornet]

Originally Posted by NeilBlanchard

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?

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

[NeilBlanchard]

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.

[GreenHornet]

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 :-)

[Christopher Jordan]

Originally Posted by GreenHornet

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.
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!

[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!

[freebeard]

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

Originally Posted by GreenHornet

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.
GreenHornet

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.



And here is Bucky's 4th Dymaxion, never built:

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'.


Frank Lee -- The next time you want to change your profile pic, I recommend you crop this:


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