Strange Brew

cannonball2 · Nov 7, 2015

This is the beginning of a build to use some parts I have had collecting dust. I got a good price on the 49cc commercial type motor awhile back and the transmission came from another too good to pass deal. Frame and wheels came fresh from the attic. Mounted up a set of new 26x2.5 knobbies and tubes and the build is ready to begin. This is a simple build using mostly repurposed bicycle parts. Building the motor mount will be the biggest fab job. For whatever the reason all the parts suppliers are out of the Cateye Pocket Bike type mounts. Using one of those would make this just about a bolt together.

This is another pedal less build similar to the Cag powered shifter trail bike. This will run the fragile Shimano Nexus 3spd. Am hoping to baby it using it mainly as different gear ranges rather than maybe a shifter. Since this is an auto clutch maybe the loading will be gradual. Who knows if it trashes I will just throw on a coaster wheel for a single speed or run down an S/A hub. Projected top speed is in the mid thirties. Shown next to my other pedal less E ride.

cannonball2 · Nov 7, 2015

Heres some details on the jackshaft. Its all bike parts except the pocket bike sprocket. The hole in the PB sprocket centers perfectly on the BB left bearing race. This is the only welding on the build, sprocket to the race, save for a bit on the motor mount, which could be purchased. The sprocket is welded to an extra race and is installed over the BB keyed washer and bearing race locking the whole affair. This is a triple reduction with an overall ratio of 17.14/1(in second/direct drive) and a top speed of 32@ 7000 which is conservative.

I have high hopes that this engine will be a good runner. Its a Chinese clone of maybe a Muryama or Mitsubishi? Anyway seems those run about forever and are pretty smooth. Its also pretty light and compact.

Intrepid Wheelwoman · Nov 7, 2015

Another fascinating bike project CB

cannonball2 · Nov 8, 2015

Thanks IWW! This is certainly a simple build. I could have run a separate jackshaft and retained the pedals I guess but they are not required in my state, so just took the simple way out. I have constantly ridden the pedal less ebike and find the foot pegs/seating position very comfortable. Important for a guy of elevated age!

curtisfox · Nov 8, 2015

Important for a guy of elevated age! So very ture in my case also. Welcome back, just love your builds. Simple and effective.......................Curt

Ludwig II · Nov 8, 2015

Where will the drive belt be, is the tank going to be a bean tin, and will you ride it facing backwards?

cannonball2 · Nov 9, 2015

The only belt will be around my waist, the tank will be the standard much maligned P-nut and it has a forward facing seat in order to avoid the massive forest of trees here.

I did see the Governor of our state ride his bike backward around the stadium at a Ga Tech/UGA game in the mid 60s. Quite a spectacle!

cannonball2 · Nov 14, 2015

Got a bit more done on this rather leisurely build, fabbed the motor mounts.
This engine was originally intended for a heavy duty brush cutter. It had in place the stand to keep it upright when set on the ground. I simply flipped it around to the inside and welded a piece of angle to it. Then made a matching bolt on section. The gap in the middle will allow adjustment fore and aft and side to side to make chain alignment easy. Will have a metal plate in the center to lock it firmly down.

Engine mounts to the bike frame next.

cannonball2 · Nov 16, 2015

A few more details. Made motor mount plates from slotted metal cut from old bed rails. I never throw away slots! There is a matching plate top and bottom which will allow major adjustment fore/aft/side to side.

I had to make a rather fussy assembly to space the BBs sprocket 1.5" outward. I had used the gear box for this build on another bike and was left with a close offset box. I found an impact socket that was a tap fit to the sprocket and centered the other end with a cone from a clutch alignment tool. Trued the whole thing on my drill press and welded. Runs perfectly true.

From what I can tell this is a 52cc engine. Cool!

Only thing missing to finish is a T8F master link--a week away! Rats!

curtisfox · Nov 16, 2015

You never seem to amaze me, you know how many of them bed rail things i scraped. Now will have to save a couple. Impact socket KOOL , sure shaping up can't wait to see more...............Curt

cannonball2 · Nov 16, 2015

Thanks Curt!

Got most of the build done. This bike is about function and not looks. It is what it is as they say. The whole build is based around what seems to be a high quality motor. I had to remove the shroud to do a few things and was impressed with what I saw.

Will add rear set foot pegs that will attach to the kickstand mounting bolt above the stay tubes. Will weld the threaded ends cut from a pedal crank to the bar and run pedals as foot pegs. Will reinstall the original chain guard, and fab one for the left side.

Now it just details, that's where the devil is as they say.

Ludwig II · Nov 16, 2015

Just out of curiosity, why didn't you point the chain box downwards instead of backwards?

cannonball2 · Nov 16, 2015

Ludwig II said:
Just out of curiosity, why didn't you point the chain box downwards instead of backwards?

That was and still is being considered, but I didn't feel the box would fare very well if the bike got dumped. In the downward position the full length of the box acts as a lever imposing quite a loading on itself and the engine. Horizontally it will tend to just skid. Its more rider friendly in the down position and may wind up there if my rear sets arent comfortable.

I started the engine briefly and its very smooth. Its also very quiet. This is what I was hoping since its from a hand held piece of equipment that would have to be fairly smooth and probably had to meet some sort of DB rating. Imagine a CG in something one had to hold!

So far so good with the build thus far!

cannonball2 · Nov 20, 2015

Well guess this one is nearly wrapped up. It just finished a shake down of several miles with no real issues. Brakes suck but that is mostly due to the old hard pads. Had to go to a double pull handle on the left as the throttle and shifter took up all the room on the right. The little motor runs like a Rolex. I found out it is the same motor used on the Uberscoot Big 50 2X.

The Nexus is working well. I shift it on the fly but totally off throttle and carefully rematch the engines speed to the road speed. So far so good. Third is pretty high but the motor will wind it out. The calculated mid 30 top speed seems about right.
Added a spring loaded idler to the primary chain, so much easier than adjustments. Once the brakes are upgraded that should pretty much have it.
Its not a looker but it rides well.

Intrepid Wheelwoman · Nov 21, 2015

Nice work CB

That's a very useful looking motorbicycle.

cannonball2 · Nov 21, 2015

Thanks IWW!

Intend to take it out on an extended run this morning weather permitting to see what its like on a longer haul. On the island here its limited by road conditions to second gear cruising. Third is too fast for pot hole dodging. The little bit of third gear time I have gotten promises a relaxed cruise.

Hopefully with care the Nexus will hold together. Three speeds are nice! Overall its a very pleasant bike which centers around a great little engine.

cannonball2 · Nov 21, 2015

So after an extended cruise the conclusion is the over all ratio is too high to pull third comfortably. I finally looked up the Nexus ratios and realized the top speed for third is 42mph. Really too high to be practical. I based my ratios on the direct drive second(31mph@7000rpm) and that was a good cruising gear. Third did ok down wind but I was bucking a 15kt north easter coming home which was done in second.

So will drop the secondary front sprocket fro 28t to 22t. That will give third a cruise around 34mph@7000.

Other than that there were no issues. This is the nicest two stroker Ive had. The SA three speed GT5 CG bike is pretty nice engine wise but not in the same league as this engine in run ability. I paid $75 for this engine shipped am glad I did!

silverbear · Nov 22, 2015

Once again you make things look so easy. This is a nice one!
SB

cannonball2 · Nov 22, 2015

Thanks SB!

I like the way it has turned out. Its a simple build with the added nicety of a 3speed hub.
Hoping the Nexus will hang in there. At least they are cheap. I bought a new one yesterday(hub only, no shifter/hardware) on ebay for $18 as a back up. If not I will dig up a SA.

KCvale · Dec 1, 2015

cannonball2 said:
Brakes suck but that is mostly due to the old hard pads.
Had to go to a double pull handle on the left as the throttle and shifter took up all the room on the right.

Simply put your 3-speed rotary upside down on the left with a short grip.

You can use longer independent brake levers for a bit more force on those C-brake pads as well.

And it's best to put the U clamp on the coaster brake arm even though you don't use it, it helps keep the wheel in place.

The Nexus is working well.
I shift it on the fly but totally off throttle and carefully rematch the engines speed to the road speed.

The nice thing about internal shifters is you can change gears sitting still, but also shift with power on.

One thing you will notice soon enough is that Nexus don't want to stay in place on the right hand side, the torque pulls the right side forwards.

The fix is to make sure your left side coaster brake arm is firmly attached so the left side won't more, then put an 'axle tug' on the right side to keep the wheel from moving forward.

It's just a washer with a threaded shaft and something to hold the back of the frame.

Most are designed for an open back horizontal drop-out.

https://www.google.com/search?q=bicyle+axle+tugs&ie=utf-8&oe=utf-8#q=bicycle+axle+tugs

Unfortunately most coaster brake bike frames are 'fish hook' open front dropouts.

I use these for my 3-speed shifters, 2 for $2 and you only need one for the right.

The Nexus hubs axle nut doesn't have a lot of play room, but that thin washer is just right.

Then it's just a matter of getting an anchor point behind the dropout.

I have used all kinds of little L shaped pieces of metal with a hole for the bolt to come through, and work just fine like this.

But usually not and you have to get creative.
Anyway... that's how you keep that Nexus from wanting to move forward.
Ohhh, one more note, do NOT torque that set screw to tight!
All it needs to do is keep the actuator attached to the right lug nut.
Tightening it too much with strip out that soft aluminum housing.

So far so good.
Its not a looker but it rides well.

I think it looks sweet, nice job.http://motorbicycling.com//www.pinterest.com/pin/create/extension/

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