Have you built a 2 wheeler?

[Teeeman]

We are trying something new to us this year... get to test it tomorrow... prelim testing looks good on the kitchen table...


How many folks have actually built and ran a 2 wheel car (carrying 2 wheels in the air off the track)?


-Terry

[Pinewood Daddy]

OK... You've teased us long enough!!! Where's the pictures!!!

[Teeeman]

OK... You've teased us long enough!!! Where's the pictures!!!

PM sent

-T

[Pinewood Daddy]

OK... You've teased us long enough!!! Where's the pictures!!!

PM sent

-T

Very interesting creation!!! Don't forget to post some video!! I can't wait to see that thing run!!

[doct1010]

How many folks have actually built and ran a 2 wheel car (carrying 2 wheels in the air off the track)?


-Terry

I believe Joe has a working prototype.

[joe]

Yes, we have one. It is very fast and pretty darn stable. It lacks about .01 sec of our fastest cars -- and I can't seem to make that up. It is a hair faster down the slope (vs. 3-wheelers) but not as fast off the start as I expected. It's difficult to get the weight rearward because the weight needs to stay low and in-line with the two touching wheels (same side). I've gotten it down to about 1 oz. on the front wheel. I'm sure it would perform like a peach if I could get it to .5 or less, as it hugs the rail better than any car I have ever seen. We have two 3-wheelers that can edge it out, one has .6 oz on front, the other has 1.0 oz on front.

Why is it not faster than these 3-wheelers? Two important points I think.
1) the weight is more spread out -- this is because of the difficulty and restrictions of the geometry of weight placement.
2) Since it has no touching wheels to balance it on the opposite side, it tends to wobble a hair over track joints and tiny irregularities in the track surface -- just enough to make the difference between winning and losing.

One of these days I'll build another and incorporate what I've learned. The car is faster when I take both the lifted wheels off of the car. If it was a true "motorcycle" I'm sure it would whip our 3-wheelers. I may cutoff the two lifted wheel "arms" and see for myself -- I'm sure that would add to the stability. I'll say this, it's hauntingly quiet when it runs down the track. I'll try to post a picture today if I can, but going out of town tomorrow!

[joe]

Photos as promised. Some of the tungsten weight is stacked behind the rear wheel. The remainder is in the pocket between the front and rear wheel, including several tungsten plates below the pocket -- these are at best about 1/16" off the track.

[PWD_addict]

That is crazy looking!!! I can't imagine the engineering that went into that. Nice work Joe!!!

[Mike Doyle]

Nicely done Joe! I was working on something similar but with two diagonally contacting wheels instead of both on the same side. It never made it to paint because is suffered greatly during the transistion from slope to flat, now its given it's life so that other derby cars may live

[joe]

A few seconds after I photographed it this morning, it decided to try and fly, rolling off the railing and crashing to deck. The crash completely severed the arm that holds the rear wheel. So trying to make lemonade out the lemons, I pulled the front wheel off too (leaving that arm), lubed it, and ran it. It was faster than ever, and beat the 3- wheelers, underweight too, at 4.75 oz.
So what the heck, I cut off the other arm to make my motorcycle. Won't work very well now, because the balance has been upset. The little bit of weight to the outside of the wheels is now overcompensating, and the car has trouble staying level. Needs a weight redistribution, and a few other modifications related to weight, then should work.

So, for a brief moment in time, the 2 wheeler was about .015 or so faster than our good 3 wheelers. Interestingly, this speed seems to come after the transition, finishing 2 - 3 inches ahead on 28' after being (maybe) 1/4" in front after slope.

[SlartyBartFast]

A few seconds after I photographed it this morning, it decided to try and fly, rolling off the railing and crashing to deck.

That really doesn't surprise me.

Consider that as soon as the raised wheels contact the guide, the car is unbalanced. The only result will be the raised wheels riding over the guide.

When the rolling wheels contact the guide, a similar unbalance is induced in the car. Too much of a bump or push and the car will flip.

For the most stability, I would think that both the front and rear wheel would have to be aligned to ride the guide.

[joe]

I'm not being clear perhaps. The car runs superbly on the rail with just the front wheel contacting the rail. The "railing" that the car fell off was my deck railing, where I was photographing it. It didn't fall off the track!

[BigSilver]

Sounds like aerodynamics are playing a substantial role as well. 1 less wheel 20% drag reduction, 2 less wheels and arms 50% less aerodynamic drag?

[gpraceman]

Sounds like aerodynamics are playing a substantial role as well. 1 less wheel 20% drag reduction, 2 less wheels and arms 50% less aerodynamic drag?

If you've decreased the frontal area of the car, then you may have decreased aerodynamic drag. It still also depends on how smoothly the air flows off of the car.

[Pinewood Daddy]

I gotta design one of those!!!

I think I'll recess the two "extra" wheels into the body to satisfy the 4 wheels rule. That will be a great conversation piece for our PWD next year.