Twin Engines

I really can't wait to see this "thing" you're going to make. I'm a little sad I won't be able to hear it though.
 
I'm gonna ask my nephew to help me shoot pics and video and post online when I'm done. I've never uploaded either before, but it's worth a try for comparison's sake.

Can't wait to charge up the hill with twin engines blazing. It will be exciting to feel the "powershift" transition between the front engine's redline and the transition to the rear engine's sweet spot. Also, to experience the "downshift", when the rear engine falters and the front engine picks up the slack.

I have a hunch that there will be no need to pedal-assist anymore, just a push off from a deadstop.
 
Why O Why?

When mention plans for dual electric motors there is almost no response? :cry:
Accept my Bud Jake.

Are they both rack mounts? Or one frame and one rack?
 
ozzy, the're both friction drive rack mounts, one in front and one in the rear.

Don't get me wrong; a front e-hub with a gas engine or rear e-hub would be sweet. In fact, i have the front hub but I don't want to deal with 80 lbs of batteries, the ritual of removing two saddlebags full, carrying them upstairs to recharge, lugging them and reinstalling them every time I ride the bike. I also don't want to pay $1K+ for lighter Li Ion batteries w/18ah to power my 72-volt e-motor. And batteries need replacing, because they don't last forever.

I must admit that my front e-hub install was clean, quiet, odorless and stealthy. One admirer commented on my neat "front drum brake".

And I know dual engines on a bike will look goofy.

In my situation at this time, e-hub is not worth the effort.
 
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I've done some calculations with online Spindle Speed-Rpm Calculator about hillclimbing.

When charging uphill with two engines pulling together, the front engine peaks at 8900 rpm and 29 mph. At this speed, the rear engine is revving 7300 rpm, which hopefully is its sweet spot. The front engine drops to idle, disengages its clutch and the rear engine runs alone. At 8,000 rpm, speed should be 31 mph. At 8500 rpm, 33 mph, at 8900 rpm it's 35 mph. Of course, speeds might be slower than calculated because of the uphill climb, extra weight, spindle drag, frictional losses,etc. But then again, speeds might be faster because of dual engine power.

I'm going to sleep and dream some more. Work and school gets in the way until Friday evening.:rolleyes:
 
If anything you'll be able to blast up most any hill at 25+ with no pedal assist at all. Lazy bugger!

Ozzy. This kinda thing gets more responses simply because people here are more attuned to bikes with internal combustion. If we posted the same two threads on endless sphere your thread would get much more attention while this one would be filled with negative nancy posts about burning fuel polluting...
 
Well, the Staton front-mounted friction drive kit was on my doorstep when I arrived home last evening. The first thing I measured for fit was the bracket that sandwiches between the front fork. Dag nabbit, just as I presumed, the mounts won't bolt onto the suspension fork's bridge. The center bolt lines up, but not the outer two bolt holes. I could probably drill the fork center bridge, but the bolt holes would be too close. I've got a sneaking suspension it'd be better to fab a horshoe-type mounting bracking for better distribution of stress. My "Girlie" bike is sidelined and will probably be donated to charity after removing its ROCKSHOX fork.

Sooo, this morning I went to the bike shop and bought the Raleigh Retroglide 7, a multi-speed cruiser bike I had been wanting to get for the past three years. It has a derailleur, v-brakes front and rear and a non-suspension fork. With wide rear dropout and cruiser frame, the bike's a good platform that'll accept HT, rack-mount, NuVinci and my old ROCKSHOX fork, once I fab sturdier brackets for the front-mounted friction drive. The only negatives are the stock nubby tires, which will be replaced when I take the bike in for a hundred-mile checkup. Then the shop will install my HD rims and tires from "Girlie".

Installation of the front-mount engine kit took 45 minutes and transferring the rear engine assembly took another 45 minutes. This did not include carefully removing both new fenders. Of course there were snags in the installation. The mounting bolts were too short to sandwich the solid fork, and the bolts supporting the struts needed upsizing. The new bike's rear dropout needs drilling oversize to 1/4" to accept Grade 8 bolts I used on my old cruiser.

ANDDD, the bike's frame(seat stays?) is too wide, so one end bolt can't be installed. Basically the mounting brackets needs to be widened about 1", or two wider sandwich plates need to be cut and bolted in. The rear mounting bracket also needs to be notched slightly to clear the v-brake arm.

I am so close to being done. All the controls are in, as well as my front basket, suspension seat and rearmost bikestand.
 
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Almost done. I got new bolts from Home Depot tonight and finished the install. Instead of fabbing/modifying the rear mounts, all I needed to do is drill a new hole in the plate, on the inside of the seat stay, closer to the center bolt.

Tomorrow, I just need to gas and go.
 
I figured I'd swap over my front HD rim and HP tire before the maiden run. Of course, when I did that the v-brake arms hit the mounts because of the wider rim. The rear v-brake also hit the mounting bracket, so I clearanced that too.

When I rolled the bike onto the sidewalk, I thought both brakes were locked! Then I remembered friction drag and when I raised both engines, the bike rolled well enough, considering the extra weight. There is massive amount of friction drag to take into consideration now, and the front engine assembly drags more than the rear drive. The new bike takes getting used to, since men's bike frames are at least an inch taller, and because of the extra 16 lbs off to the left front.

So I walked my bike to the nearby park and picked a remote location. The rear engine started with two pulls. The front engine started in three pulls and both idled well. I sat down for a 5-minute water break and let the new engine start the break-in. It sounded much crisper than the rear engine. Maybe because it was tight, and the mass of the lighter spindle allowed it to rev quicker.

In a couple minutes, I was driving down a medium-size hill using both engines. The rear engine felt weak. It took a few minutes of driving to warm up, and there's that extra resistance with the front engine idling.. When the new engine kicked in, I am SOOOO glad I chose the 1.25" roller instead of another 1.5" spindle. Acceleration is UNBELIEVABLE! The engine needed break-in, so I kept the revs reasonable. There is a definite major power boost at low and medium end with dual engines. It could be a number of factors that made the front engine more responsive, such as smaller-diameter spindle, HD rim and slick tire.

All was going well for three miles, when I floored the new engine and it immediately died. And it's still dead and unwilling to start. I yanked that pull start numerous times but it still won't start. Driving with the rear engine only was sluggish until I remembered the front engine resistance. When I raised the new engine, it was much easier for the rear engine to drive home. When the new bike charged up the medium-sized hill, it was much easier than previously, because the 7-speed option helped when the engine needed it.

Everything went well until the new engine quit. I felt the power of the dual engines, and it was awesome. If you start off with the front engine then kick in the rear engine, you can feel the little extra help. When you're at low speed with rear engine only, you can SERIOUSLY feel the extra help from the new engine and smaller-diameter roller. I only have three miles on the dual-engined setup, so I can't comment much on it. There's no smoke in the face from the front engine, and the extra noise at idle and speeds below 15 mph was very little. When the new engine breaks in, there will be serious power and acceleration available!
 
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