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Thread: The ElMoto Dream Bike

              
   
   
  1. #161
    teddillard
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    Quote Originally Posted by Mike Edwards View Post
    Richard230 is right though. On the street it is debatable whether the frame flex issue is even noticeable over the additional 100 lbs+ weight from the batteries.

    It may even be barely discernible on the track when your bike weighs over 500 lbs but it will be a factor, especially with the swing arm.
    So, is it fair to assume that, with a stock CBR1000, if we replace the stressed motor with a similarly stressed battery box and such, and keep the swingarm and front end intact, as well as keeping the C/G and weight distributions similar we can't screw it up too bad for the street? Since you're talking the upper 2% of handling performance, I can't see it to be much of an issue for our dream bike, with the normal caveats we'd use for any build, really. (Your advice - to note the design and weight distribution of the frame, keep in mind the ICE is a stressed member, etc is always good advice starting out on a build.)

    I guess I can't see how we could make the bike more rigid even if we wanted to...

  2. #162
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    If you can keep the weight distribution right then you will probably be okay. MIght be easier with a bespoke frame though, particularly as they don't have to be that expensive.

    A friend has just built a replica of a Ducati twin spar frame. He started with the headstock angle and the swing arm mount and simply filled in the pieces form there.

  3. #163
    Senior Member Spaceweasel's Avatar
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    Man, if only we could find an aluminum framed bike with modern inverted forks that wouldn't be compromised by losing it's load bearing engine when we ditch the ICE components...

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  4. #164
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    Quote Originally Posted by Spaceweasel View Post
    Man, if only we could find an aluminum framed bike with modern inverted forks that wouldn't be compromised by losing it's load bearing engine when we ditch the ICE components...
    You mean pick one that is already massively compromised from the outset?

  5. #165
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    Quote Originally Posted by Mike Edwards View Post
    They may not have fully understood the amount of flex they were introducing but the steel lattice style frames Ducati used for years worked well...
    As I recall, the early 900 Monsters had an even smaller diameter diagonal brace near the steering head. 6-8mm in diameter? Maybe a solid bar?:



    ducati Monster 900 94 1.jpg

    It probably was easy to cut out and weld in different stiffness tubes(or bars) in this area, to optimize the corner handling of the pre-production prototype. This could be done right at the test track, without disturbing many components of the bike, because of the exposed nature of the frame-a flexibility(pardon the pun)of design to think about for those considering a conversion.

  6. #166
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    What you need is something like my old Aprilia RS50. As near as I could tell, the motor provided absolutely nothing to the structural integrity of the frame and the chassis seemed pretty sturdy to me. Unfortunately, the frame is kind of small for an elmoto conversion, unless you used a hub motor.
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    Richard - Current bikes: 2014 14.2 kWh Zero S, 2016 BMW R1200RS, 2011 Royal Enfield 500, 2009 BMW F650GS, 2005 Triumph T-100 Bonneville, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior.

  7. #167
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    Quote Originally Posted by Richard230 View Post
    What you need is something like my old Aprilia RS50. As near as I could tell, the motor provided absolutely nothing to the structural integrity of the frame and the chassis seemed pretty sturdy to me. Unfortunately, the frame is kind of small for an elmoto conversion, unless you used a hub motor.
    Think you are missing the point. The RS50 had neither the power nor the weight to flex the frame Stick 100 lbs of batteries in there and it will fold in half.

  8. #168
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    Quote Originally Posted by Mike Edwards View Post
    Think you are missing the point. The RS50 had neither the power nor the weight to flex the frame Stick 100 lbs of batteries in there and it will fold in half.
    I would be surprised if that happened. The frame seemed much stronger than say a 1980 Honda CB750, or many other Japanese bikes with a chassis design using a steel tube backbone. Plus, the RS50's motor and it's 3.5 gallons of fuel must have weighed about 75 pounds and I didn't hear any creaking when I pulled the motor. I have owned lots of small motorcycles over the past 50 years and this bike had the most robust frame that I had ever seen in a motorcycle 500 cc or under. It certainly seemed much stronger than my GPz305, or my 250 Ninja, and the frame also seemed to be built stronger than the one on my VFR700FII, just to name some examples. If there was a weak point in the chassis, it might have been the swing arm, which was typically what you might have seen in a Japanese 250. But that frame was massive and well supported by interior webbing.
    Richard - Current bikes: 2014 14.2 kWh Zero S, 2016 BMW R1200RS, 2011 Royal Enfield 500, 2009 BMW F650GS, 2005 Triumph T-100 Bonneville, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior.

  9. #169
    Senior Member ARC EV Racing's Avatar
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    Re: The ElMoto Dream Bike

    Quote Originally Posted by Mike Edwards View Post
    Think you are missing the point. The RS50 had neither the power nor the weight to flex the frame Stick 100 lbs of batteries in there and it will fold in half.
    I think this problem is pretty much self limiting. Smaller frames are generally designed for less weight but then they don't have the space to fit a massive battery pack anyway.

    We did an rs125 road bike conversion and there was only room for an agni and about 4kWh of A123 cells. Finished weight wasn't much different to the original.

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  10. #170
    teddillard
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    Quote Originally Posted by ARC EV Racing View Post
    I think this problem is pretty much self limiting. Smaller frames are generally designed for less weight but then they don't have the space to fit a massive battery pack anyway.

    We did an rs125 road bike conversion and there was only room for an agni and about 4kWh of A123 cells. Finished weight wasn't much different to the original.
    Right... I think it's pretty much a non-issue after reading through again, due (and great) respect. Keep the weight about the same as what the frame was designed for. Keep the C/G about the same. Keep the structure as much the same as possible, and go for stiffness over trying to second guess the original design's flex. In the worst case you'll lose maybe indiscernable handling at the highest limits of performance, if you somehow accomplish what I think is fairly impossible - to make the frame more rigid. But I'm keeping an open mind.

    "Folding up", "massively compromised", "screw up"... maybe a little overstated? Keeping in mind there are somewhat huge differences between what makes a good roadracing frame and what makes a good, high-performance street frame?

    As far as designing and building a frame, I sincerely doubt we could build a significant improvement on the top of the industry's designs today... This is just my personal opinion, but decades of the top racing teams and manufacturers throwing money at frame design has got to mean something.

    ...and just to subject myself to ridicule, I'll say it again. I think the double-steel-downtube frames, starting with the Norton and on through to the Yamaha roadracers of the '70s were in many ways the apex of the frame builder's art.
    Last edited by teddillard; 18 February 2013 at 0510.

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