What about a proper comparison, 3 wheels vs 4.

[Mick]

I have searched the internet but can not find the answer, here is the question,
All things being equal, engine, power, weight of vehicle, what would go round a track quicker, 3 wheels or 4?

[stretchmobileski]

Usually the three wheeler saves weight and drag by losing the 4th wheel and suspension. The draw back is loss of traction. I've never seen a comparison like you describe either. Trikes are usually lighter and bikes are even lighter yet.

[Liteway]

All other things being equal, 4wheels are going to provide more stability than 3. As an extreme example consider a 3 wheeled CRV. Frightens me just to thank of taking an evasive maneuver in such a vehicle.

[Mick]

At school, a long long time ago, we used a tripod for the gas burners in the chemistry lab as they were more stable. Just looked at the Chevy powered Vigillante, got one wheel at the front but engine is between the rear axles and has perfect weight distribution on all three wheels. Makers say it had the cornering power of the Maclaren F1 supercar.
Do you get the UK TV show, Top Gear over in the States? It would be good to put some production reverse trikes around the Top Gear track and compare the times to others.
Another British show, 5th Gear tested a T. rex but in heavy rain, not a fair test, although they did love it!

[mtntech]

Aug 31, 2014 8:47:25 GMT -5 Liteway said:

All other things being equal, 4wheels are going to provide more stability than 3. As an extreme example consider a 3 wheeled CRV. Frightens me just to thank of taking an evasive maneuver in such a vehicle.

What do you mean by 3 wheeled CRV? I think Mick poses a valid question, and one I don't have a clear answer for. I will say that a 4 wheeled vehicle may have more weight in the rear that is further away from the roll center (middle) of the vehicle.

[Liteway]

CRV. As in Honda CRV or any sport utility. Yes I know, they have 4 wheels, but I was speaking of a hypothetical 3 wheel version to make a point.

Any 3 wheeler has only one axle to oppose roll. In rapid braking with a 1+2, weight transfers forward. If you attempt to turn at the same time, the vehicle destabilizes as there is no roll opposition at the front. This is why those big touring rigs can be made to flip over in a gas station driveway at a rediculous low speed. 2+1 is stable under braking, but less so under acceleration while cornering for the same reason. Weight transfers to the rear where there is no axle to oppose roll. This is where you get the inside front wheel to lift as the front end goes light, and the heavy rear with no roll resistance tries to twist the whole shebang onto its head.

Yes, I know these effects can be countered or minimized with a low cg and proper front/rear weight distribution, but they cannot be eliminated except by adding a 4th wheel.

Get real fellows. I probably like 3 wheelers as much as you, but for non-dynamic reasons. Simplicity and ease of build, light weight and maybe some airo advantage. Also they are a little weird and I like that. But there is a reason there are no competitive racers with 3 wheels, and its not by chance and not because of the rules. Racers look for every little advantage. If three wheels worked better, that is what they would all have.

[Mick]

Your answer is still hyperthetical and based on what you have read but not experienced? I want a proper comparison.

[mtntech]

Converting a 4 wheeler to 3 wheels for a comparisons sake doesn't make sense to me. I am looking forward to taking on 4 wheelers on the street with my purpose built 3 wheeler.

[jim99]

Hi Mick,

This is probably not an equal comparison, but here goes.

I raced open wheel cars for twenty years on asphalt ovals. The cars were powered by various Suzuki sport bike 750cc engines. 8” wide slicks on left side, 10” wide on right, 950lbs, and four wheels.

I have built two reverse trikes and have auto crossed both. The auto cross tracks were large parking lots with orange traffic cones to mark the course. The trikes were/are powered by 750cc gsxr and now a 1300cc hayabusa. Approximately 1,100 lbs and street tires ( Yokahama S-Drive) (great gripping tire for the price) and three wheels.

I have also run some laps on a 1/4 mile asphalt banked race track with the Hayabusa.

Race car – stab the brakes hard on corner entry to slow car and cause it to start to rotate while still slightly on the gas. By center of corner start adding gas and by ¾ of the way through the corner hard on the gas. Turn left and repeat twice each lap.

The Trike – Everything is the same until the center on the corner when the rear tire is at maximum lateral load and you start to add power the rear tire gives up grip extremely fast and the trike spins out. It is no whereas as controllable as a four wheel car spin. Happens really, really fast

Just my two cents, you may experience different results.

Your, Jim

[Liteway]

Jim, you didn't say about how competitive the trike was at the auto cross. I would think this is where one would work best as the relatively low speeds would allow better control of the slides. Back in the day, I used to autocross a 60 model Austin Healy 3000 converted to small block Ford power. It loved to hang its tail out and was a wonderful auto crosser. I think my trike would scare the crap out of me on a high speed road course for the very reason you describe but I would love to autocross it. Trouble is most events here are SCCA and its my understanding they do not allow 3 wheelers.

[mtntech]

Sept 2, 2014 20:56:13 GMT -5 jim99 said:

Hi Mick,

This is probably not an equal comparison, but here goes.

I raced open wheel cars for twenty years on asphalt ovals. The cars were powered by various Suzuki sport bike 750cc engines. 8” wide slicks on left side, 10” wide on right, 950lbs, and four wheels.

I have built two reverse trikes and have auto crossed both. The auto cross tracks were large parking lots with orange traffic cones to mark the course. The trikes were/are powered by 750cc gsxr and now a 1300cc hayabusa. Approximately 1,100 lbs and street tires ( Yokahama S-Drive) (great gripping tire for the price) and three wheels.

I have also run some laps on a 1/4 mile asphalt banked race track with the Hayabusa.

Race car – stab the brakes hard on corner entry to slow car and cause it to start to rotate while still slightly on the gas. By center of corner start adding gas and by ¾ of the way through the corner hard on the gas. Turn left and repeat twice each lap.

The Trike – Everything is the same until the center on the corner when the rear tire is at maximum lateral load and you start to add power the rear tire gives up grip extremely fast and the trike spins out. It is no whereas as controllable as a four wheel car spin. Happens really, really fast

Just my two cents, you may experience different results.

Your, Jim

That's why I didn't build a rear wheel drive trike. I believe that a RWD trike is fundamentally flawed when it comes to putting the power to the pavement.

[Mick]

So what you are saying is that there is no problem with stability but rear end grip at extremes?

[Liteway]

Mntech; Is your differential of the limited slip or locking type?

Mick; Thanks for starting an interesting discussion.

[mtntech]

Sept 3, 2014 7:42:18 GMT -5 Liteway said:

Mntech; Is your differential of the limited slip or locking type?

I've got an open diff right now but will upgrade to a LSD when it hits the street.

[jim99]

Auto cross was a local sports car club event which I belong to. They let me run the course, but did not class me, so in my mind I was a class of one and I was the winner.

Mostly I just used it to find the limits of the trike and have fun standing on the gas in first gear.

As for what works the best or what is flawed. Every wheeled vehicle built has flaws. A two seat sports car does not work for the soccer mom with four kids, the mini van does not work well for the middle aged guy trying to pick up hot dates. Neither works well as a dump truck.

Build something and go have fun with it! I doubt any of us can build the perfect vehicle, no one has yet.

Just my two cents, your results may differ. 

Jim

[srx660]

Probably the best explanation is on the RQ Riley website. He states the case for a public street vehicle. Racing is a different matter entirely. I, personally am not interestes in how fast i can go, can i beat the guy next to me, can i out corner that mazda rx2, etc. I just want something different than the cages factory's build and to be able to say that i built it myself, even if it has problems because i am not a auto engineer.

www.rqriley.com/3-wheel.htm

SRX660

[1983JZR3W]

The Riley website is a very interesting read. Thank you for posting it.

[Mick]

I've read that before, interesting. Also interesting is the Vigillante details, not a reverse trike but one wheel at the front and two at the back, Chevy powered, very stable and has perfect weight distribution between the 3 wheels.
here is the link www.vigillante.com/

[Liteway]

I would like to see an independent evaluation of that vehicle to verify the lofty claims.
Campagna claimed 1.3 g on the skid pad, 3.9 0-60, 12flat for quarter with the Kawa 14R 197 hp version of the rex. Only instrumented independent testing I could find on the net (Edmunds, Youtube.) 0-60 4.5 12.6 quarter and get this; .89g on the skid pad. The pad figure is about what I would expect from a good sports sedan or a so-so sports car.


Would it be fair to compare the capabilities Of a T-Rex to an Ariel Atom or high powered version of a Caterham?

Which would you prefer to use for a track day?

I have no proof, only an intuition the 4 wheeled vehicles would be a lot less of a hand full at racing speeds.
It would seem to me the 4-wheeled vehicles are made for racing and T-rex , if what I see on the net is any indication, is made for profiling.

Quote from Motor Trend:
"You may think we are mad, but this three-wheeler could have too much oomph for it own good. Unless you"re a professional racing driver, you will never use more than about 55 percent of the T-Rex's potential. Why? Because if you try to push it any harder on normal roads nearing its ballistic 11000 redline the rear tire will light up and you'll be heading backwards into the scenery before you can say Kawasaki Ninja. On a racetrack you can approach its limits but still need F1 driver-like skills and cojones in order to get anywhere near them".

I have had guys ask why I did not use a one liter engine or a turbo charger. Totally useless, at least at my trikes weight and my/ most people's limited skill level.
Don't want to speak for Jim, but think this Motor Trend exert is also consistent with the racing experience he described above.

Its inherent in the configuration. Adding a more powerful engine at some point simply overpowers the chassis.

Not to say its not a huge amount of fun. Just not as stable as a 4 wheeled vehicle.

[Liteway]

Note. I did a number of corrections, additions etc. to the above post during the day today. Guess I got too much time on my hands. No one had responded yet so I thought that would be Ok.
Come on guys, there is plenty of red meat here and the forum is sooooo... dead. Maybe this topic has been flogged enough? Comment on something else. Better yet start a new thread.
Pardon me Dave while I step up on your soapbox.
A forum is only as interesting as its members make it. If we all just log in every now and then without contributing what does the next guy see? Surely you guys have opinions, tech info, encouragement, criticism or my favorite contribution, simpleton B.S. Stop keeping it to yourself. Lets soup things up a bit.