mounting motor on/above top bar - massif fatbike

M

misterb

New Member
Wanted to get some thoughts from the experts here -- what about the possibility of mounting a motor above the top bar on a Mongoose Massif (20" fatbike) by using a longer seat post to make it 'adult sized' like the pic below:

DSC_0202.jpg


Ideally a small 4stroke and a qmatic if that were possible.
 
I have seen it done with a GX-35 clone, but it takes a lot of fab work, jackshaft, etc. I would add a friction drive kit instead to preserve those great disc brakes.
Where did you buy that thing? I want to test drive one myself.
 
I haven't picked one up yet - one of the neighborhood boys got one and I was envious :) I found the pic above online. I guess I could live with a friction drive, but only if I could center it - I have a thing for symmetry, can't stand the motors hanging off to one side.

I haven't seen them in stores yet - you can order online via walmart, target, academy sports, etc for < $200
 
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Offset mounting the engine on a friction drive setup allows you to mount the engine lower, for better handling. The lower cg really helps when leaving and approaching a stop.
If you mount a fuel tank or cargo box on the opposite side of the rear wheel from the engine, you can maintain some symmetry.
 
Kooool if it were me and realy wanted to do it I would cut the tubes off and make new. Nice curved drops loop and maybe split the top into two out around the motor if needed just my thoughts...........Curt
 
curtisfox said:
Kooool if it were me and realy wanted to do it I would cut the tubes off and make new. Nice curved drops loop and maybe split the top into two out around the motor if needed just my thoughts...........Curt
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I think it IS a steel tube bike so at least it'd be easier than aluminum.
 
Not being a naysayer but I always look at things with safety or the potential for injury in mind. I can't help but think what would happen in a sudden stop with an engine mounted high between your legs. Not a pretty thought.

I'd have to explore another option to motorize that one. Friction or rear rack chain drive would be a better choice, me thinks.

Tom
 
2door said:
Not being a naysayer but I always look at things with safety or the potential for injury in mind. I can't help but think what would happen in a sudden stop with an engine mounted high between your legs. Not a pretty thought.

I'd have to explore another option to motorize that one. Friction or rear rack chain drive would be a better choice, me thinks.

Tom
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good points to consider!
 
lowracer said:
misterb,
Like you were thinking, I mounted an engine to my top tube via a piece of angle aluminum. I run the chain to the large chainring via a front freewheel and then another chain from the small chainring back to a 9 speed cassette. It worked out really well!
Here is the link
http://motorbicycling.com/showthread.php?t=50454&page=13
-Lowracer-
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wow - thanks, that's just the kind of thing I was looking for. I actually already have a gx31 I got for about $50 on ebay.
 
In my opinion the only thing that will not totally jack the looks up of that bike would be a nice custom built friction drive set up, anything between the seat post and the handlebars is not gonna be nice looking and I'm with Tom on the safety aspect.

cool looking bike for sure but the engine and drive set upo needs to be at the backif I were doing it.

Here is a set up that would work good on that bike, sets the engine center of the bike, no good up close pix of the design but it wouldn't be that hard to build from what I can see.
http://youtu.be/Ec03Vbd1_yM
 
regarding saftely concerns, if i really wanted to stick with fat bike with 7 speed cassette, i could just move to the dolomite (if I can find enough room within the frame):

NewCassette2_zps8b003d29.png
 
curtisfox said:
Kooool if it were me and realy wanted to do it I would cut the tubes off and make new. Nice curved drops loop and maybe split the top into two out around the motor if needed just my thoughts...........Curt
Click to expand...
I'm with Curtis on this. If I was going to motorize that bike, and it would be cool, I'd modify either the top or the down tube to accomodate a 2 stroke in frame installation.
That will require some fabrication, tube bending and welding but it would be worth the effort in the end. You'd also have to get creative to retain the rear disc brake but it can be done. Good luck. Let us know what you decide.

Tom
 
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Yes there was a gear case.
I've ridden that bike, or one just like it, with that weird engine installation. That chain running down next to my leg was scary. I kept imagining it breaking and wrapping around my neck. Not a great idea.

Tom
 
I was thinking that you could mount a typical beach cruiser chain guard on the motor chain. Then I realized the the chain guard would need to be a left side drive version to work.
 
fabricating a chain guard for that set would be very sime and if I had a bike like that it would dang sure have one, there would be at least one or maybe two guide rollers built into the guard also, a chain that long needs something to insure alignment and correct tension in my opinion, or one wrong bobble during a leaning turn and that chain could come off.

myself Im not sure Im a fan of an engine being mounted up under my chin while Im cruising down the road at 30 mph....lol!

map
 
Regarding my top tube mount, I use a piece of angle aluminum to guard the drive side of the chain more for oil flying up, than for safety since I've never had the engine driven chain fly off. The chain from the BB back to the rear cassette came off once or twice in the beginning, but I fixed that by mounting a larger chainring to the inside of the 24T chainring acting as a chainguard.
I thought about running all chains within chain tubes (similar to a recumbent) but since I haven't had any more derailment problems, I didn't.
-Low-
 
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