Volta project

[worldpax]

Hello,

I am planning a simple reverse trike. Have some drawings and ideas right now and next week off to do a full size mock up in wood. Plan is for electric power with a 72volt 650amp AC induction motor and as many amp hours as I can afford, maybe 100-160. VW front end, single seat trellis frame chassis, but from what I've seen I'll be doing something a bit different at the back.

With the chosen motor and gearing I should be putting 450lb/ft of torque at the contact patch from 0-4000rpm, for some really fun acceleration, but the top speed might only be 75 or 80mph, maybe a little more if I can keep the frontal area down. It's about now you guys are saying, "Hey Pax, you know these RT's aren't really famous for rear wheel traction."

Instead of the standard MC swingarm at the back, I'm going to use a triangulated 4-link to try and dial in the weight transfer. The SUB-3 kind of does this with a single sided swingarm. Mine will be on both sides of the wheel.

I am somewhat mechanically inclined, but no master craftsman. Luckily my next door neighbor is a CNC machinist with his own shop. I'll try not to bug him too much, but if I get in a pinch...


Anyway that's what I have. Pics to come when I get the mock up started. Love to hear from the group. 

Pax
Tulsa, OK

[worldpax]

Basic drawing. 




Electric bike I built. 35mph top speed, 30 mile range. Really learned a lot putting it together. Need a big one now.

[captainamerica]

Sounds like an interesting project, let me know if you need help on the design side of the suspension, I dabble in the black arts of suspension design from time to time.

-Andrew

[worldpax]

Thanks Andrew. The VW front is pretty straight forward, but I think I'm kind of breaking new ground at the back. Who knows, are there really any new ideas. The four-link rear suspension is pretty tried and true in drag racing. Not that I have any experience with them, but I've read up on them quite a bit.

I'm going to have two swing arms spaced vertically about a foot. Both will have multiple pivot points at the front and rear so I can adjust the weight transfer and squat. The lower swing arm will be pretty standard and extend straight back. The upper swing arm will extend back at a 20-25 degree angle from the outside edges of the chassis to the axle carrier. The wheel and tire (automotive 225/50/15) will ride on a motorcycle axle with a custom hub. The axle will bolt to plates (axle carrier) on either side of the wheel that will attach to the pivot points at the end of the swing arms.

What I hope to gain with this is better overall control of the rear contact patch. Both in a straight line and when exiting corners. I hope this explanation makes sense. Your trike is pretty awesome, I'm sure this is something you could knock up in a day or weekend if you wanted to give it a shot or think this idea has merit.

I may get some more cheesy graph paper drawings up in the next couple days.

[Liteway]

The four link rear is a great idea. I have given it some thought too. There is an advantage you did not mention.
It negates the need to locate the front pivot point behind the drive sprocket, Instead allowing pivots to be located below and above the sprocket. The geometry of this means the chain tension need not change as the rear axle moves through its arc, promoting a smooth ride and power delivery along with increased chain life and fewer adjustments. It also allows tidier packaging because with the same arm length, the wheelbase and overall length can be shortened, giving the trike better proportions and a tighter turning circle, a big deal if you have no reverse.

Knowing all this, I still went with a conventional 2 link rear, because its simpler and easier. Building a trike is a big task and once into it, simpler and easier became a priority.
I also fretted about being able to properly engineer it to withstand the twisting load placed on it while cornering.

Hope you can get it done.

[worldpax]

Thanks for the encouragement triplethreat and I hadn't thought of that advantage. I have bad news though guys and gals. My CFO (wife) finally asked how much this little project of mine is going to cost. While she's been supportive of my creative endeavors, and I have been able to sell them off and recoup most of the funds invested, she doesn't believe that can happen with this one. So my budget has been cut in half which means no electric drivetrain. I'm going to have to use a bike motor. The great thing about the electric was that I could have put all the batteries under my legs towards the front and only had the 8"x11" 60lb motor behind my butt. All the weight would have been low and well distributed. So it looks like there's going to be some more design and research. Off hand, how much longitudinal chassis space did you need for your motor. 2 feet, 3 feet?

[Liteway]

20 inches including headers, not pictured.

[worldpax]

Thanks again triplethreat. I did some rough calculations on my CG. With the electric drivetrain I would have been right at 30% of my wheelbase. With the gas engine it puts me at 46% back on the same wheelbase or 39% back on a foot longer wheelbase. Based on those numbers, with a worst case being a CG at 46%, is it worth ditching the VW front end and building a double wishbone that I can locate further back? I could also do the split the beam thing on a VW.

Current rough up without the skin.

[Liteway]

I know little of v dub front-ends, so maybe someone else can help you with that one.
Where to locate fore/aft cg? Different opinions here. I say it depends on pwr/weight ratio you expect to achieve. Best stability requires weight up front. High power requires weight aft if decent traction is to be achieved. Mine is 47/53 with about 6 lbs/hp. My handling is better than my traction. If you plan high power, plan on fitting the most grippy rear tire possible.

Most will agree that keeping the Cg as low as possible is a good thing, and if low enough, up to a point, will help compensate for more weight aft.
That's my opinion. Others will differ.

[worldpax]

Apr 19, 2015 9:02:06 GMT -5 Liteway said:

I know little of v dub front-ends, so maybe someone else can help you with that one.................
.........................Most will agree that keeping the Cg as low as possible is a good thing, and if low enough, up to a point, will help compensate for more weight aft.
That's my opinion. Others will differ.

Good to know. One benefit of going with the gas motor is that I'll have a transmission now, so I can use a 16 or 17" rear tire and that opens up a world of wider-high performance tires. I was sticking with 15" on the electric to help with gearing.

So I will have a wider tire at the back, possibly 245-275/50/16. And my hope/dream/delusion is that the four link will allow me to get the weight to the rear even with a more forward CG. I'm no expert, but I have done pretty well in autocross with street cars and a shifter kart. Hopefully some of that knowledge will transfer into being able to create a trike that doesn't roll over, handles well, and can put the power to the ground.

BTW- of course I'm looking at Yamaha R1, ZX-10, GSXR-1000 engines