Rack mounting a chinagirl

[maniac57]

Lately I've been thinking of a way to use some of the full suspension bikes I have laying around.
I'm leaning towards rear mounting the engine on a rack above the wheel and using the regular chain drive/ragjoint setup since I already have several rims assembled with sprockets.

This would allow the suspension to function without chain problems and looks like it will work quite well. I'll simply cut the intake manifold to use the straight section which will level the carb nicely. I will mount the tank above and behind the motor on a stand. The pipe will be easy to route along the framestay.


This is a mock up on the narrow crank german made Sears frame I am currently messing about with. This would instantly solve all crank clearance issues too!



Roughing out the engine cradle with some welded steel angle and a section of frame tube. Also have a rear rack-like section of pocketbike frame that will make a good solid platform for this. I'm hoping to have a chain adjustment feature built right into the motor mount. The rack section with the motor and mount will attach to the rear framestays.
One worry is the length of the cables...
another is butt clearance from the spark plug and head...
But it looks doable and I have seen very few rear mounts.
Opinions?

 

[bluegoatwoods]

It does look do-able, I gotta admit.

But won't you still have to deal with chain loosening/tightening when the suspension flexes?

 

[maniac57]

Not with the engine mounted to the rear suspension swingarm. It all moves as one unit.
There are some differences between mounting it on a regular bike and the suspension bike so I'm going with a mongoose frame I found somewhere for the initial design. The pics are from a solid frame and I'm not going to bother with this style frame just yet. I like the idea of opening up a suspension bike market for chinagirls with a true bolt on, but the first few prototypes will probably be welded solid to the frame. Time will tell.
I'm thinking seriously of making a kit if it works out like I hope, but first things first.Have to see if it works.

 

[2door]

Somewhere, way back, a member posted a picture of a rack mounted HT. He had done a very nice job of it and the little engine looked like it belonged back there.

There was also another bike, I'm talking maybe 2008 or 09, that was a twin engined affair. One HT was in-frame, the other was rack mounted. I have no idea where I'd find those today but if they turn up I'll post them here. Maybe someone will remember those oddities and will refresh my memory as to where I can find them.

Good luck with your project. Sounds interesting and feasible. Keep us posted.

Tom

 

[maniac57]

The longer I stare at it, the better the idea looks considering how cheap and numerous the suspension bikes are.
I'm finding it hard to believe nobody else has had this idea before. I really expected a lot more input from other with similar brain(storms)farts.
It just seems so easy and universal...
I'm hoping it works as well as it looks.

 

[Wickedest1]

Butt clearance...lol...

Butt seriously...lol

No this looks awesome bro...
Try easing the motor behind about 6 inches...

A neighbor did a rack mount 48...

Walmart seatpost rack...tigged some aluminum supports to the rack and bolted down by the rear axle...

2short aluminum tubes tigged to the plate on the rack and the chain ran down thru the side slot...

On a full suspension too...it works well...

You can definitely do it...

Good luck brother

 

[cannonball2]

This is a great idea, for the plentiful CG engines. I have built several rear mount full suspension bikes using 4stroke engines. Kind of an apples/oranges comparison but it may show how easy a susp. frame can be modded. If you made a pivot type mount with two supports that were slotted chain adjustment would be a snap! http://motorbicycling.com/showpost.php?p=336558&postcount=10

 

[maniac57]

Did some more fiddling today.
Got the rack setup welded on solid


Welded a cradle on to hold the motor. Looks nice and solid. Can't deflect it by pulling on the head so it should be fine. The pipe will be easy to run as well.


I still have to bob the intake to level the carb.

 

[16v4nrbrgr]

Nice job Maniac, a rack mount that will have some serious 66cc torque! Most rack mounts use the whacker/pocketbike engines that lack in that dept, and I'm thinking about upping the displacement of my BMX using a 52cc pocket bike engine to be able to gear higher and still enjoy the torque that only CC's can supply.

 

[gokart25]

I've been considering selling my 4 stroke stuff... Just wondering if something like this would work with a 79cc predy? I like the design!!

 

[maniac57]

The only issue I see using a four stroke would be the lack of a gear reduction. This would require a much larger rear sprocket to work correctly, but I see no reason any engine could not be used.
I decided to use a pocketbike pipe rather than the stock muffler so I won't have to do it again later.




Still need to build a fuel tank stand and hook up the throttle and clutch cables.
Might need to jack up the spring preload as well to prevent the seatpost hitting the motor. Seems a bit soft as is...

 

[maniac57]

Duplicate post. Friggin ancient laptop.
Mods please delete

 

[maniac57]

Throttle and clutch mounted and ran cables. Little bit short but still workable. No pulling or binding when turning the bars any normal amount.

Still need to fab tank stand and find a front tire and tube before testing begins.
Too cold and wet for any fab work today. My hands hurting too bad from the cold.

 

[Intrepid Wheelwoman]

Great work Maniac That is a very nice set up, I'll be eagerly waiting the first road test report once the weather improves.

Now I'm starting to wonder how a China Girl would work out mounted over the front wheel of a bike

 

[maniac57]

From what I can see I.W., this same style mounting would work just as well over the front wheel. Just be sure the road is dry and the front wheel is straight when bump starting.
A good solid rack would be easy to build....sprocket does not care what wheel it's bolted to.
By the way.....I believe this would also work quite well to mount a ht on the Walmart Mongoose fatbike! No jackshaft reqired! Just possibly a sprocket adapter or some type of spacer for the ragjoint sprocket.

 

[maniac57]

Now Labrat or Josh Moon or one of our other clinically insane members will probably build a two wheel drive Rokon tribute bicycle....

 

[Wickedest1]

Nice rack...lol

You are a maniac sir...

Feel free to continue as such...


Hows the heat on your hiney tho...

Gotta be a bit warm...

Oh and why wait on lab or josh...you just did a rear rack chinagirl....
zip some pieces together and trow a kit on dat itchbay....

Seriously just do it...

Are you doinng it yet?

 

[maniac57]

I would NEVER do something so outrageous!
I'm shocked and appalled you could think me capable of such a heinous act!
* pushes something behind something else, locks door, mumbles profanities*

 

[Desert Rat]

I'm still waiting for the CG unicycle

 

[maniac57]

Did a bit more today. Built a tank stand and mounted the tank.
Unfortunately, I started feeling quite poor and did not get around to mounting a front tire and testing the setup.
Tomorrow hopefully.