Pocket bike project - ideas?

Status
Not open for further replies.

SpyGuy

Hooligan
Messages
406
Reaction score
1
Location
Tucson, Arizona
Okay, I'm planning to do the pint-sized pocketbike idea from the planning section, but I wanted to get some input from you guys, too. Right now I'm just gathering parts and information.

-Welding: I only have one of the 90-amp MIGs (110v) from Harbor Freight for my welding - too expensive to get the house rewired for 220v, plus it's not my house, anyway ....

-Motive power: engine will be a 47cc pocketbike engine with a CVT transmission. I'm not looking for high speed - already got several store-bought (okay, craigslist-bought) pocketbikes for that - I'm just looking for casual cruising. Plus, I didn't feel like messing with the jackshaft setup.
-Exhaust: An exhaust can from a goped may be the way to go, although I'm thinking I may cut up one of my old busted pipes and do some creative rewelding for a custom pipe.
-Wheels: am going to be getting a set of 4" or 5" goped wheels with chain drive. Luckily, the chain drive is with #25 chain, which is what the pocketbikes use, so I'm good there. I also discovered that several of the electric scooters use the same size chain drive.
-Throttle, brake levers, etc.: I have a stash of pb parts I can use for all this, so all i really need to do is the frame and forks.
-Seat: would be either a regular minibike seat, possibly one of the ones off a scooter.

-What kind of tubing should I use? Conduit? I was thinking 3/4" thinwall, with 2"-3" pegs to hold the frame together at the joints, obviously as well as welding. I want to make this thing small and light, yet strong enough to hold my 200lbs.
-Front forks: was thinking about building a set, though in a pinch, I suppose I can use a pb set. I think building would be cooler, though.

Anyway, so let me hear what ya think. Remember, I'm not trying for top-end all-out speed (although that may be on a later build), just something small and fun to cruise around on, and easy enough to put in the trunk of a VW. (Yes, I DO have a VW Bug, just like the one in the picture!) Mainly I'm concerned about the structural elements, and making sure I get it strong enough.
 

SpyGuy

Hooligan
Messages
406
Reaction score
1
Location
Tucson, Arizona
No, the "New Beetle" is the "New Beetle" - no two ways about it. The "Bug" will always be an air-cooled rear-engined car designed by Dr. Ferdinand Porsche, made somewhere between the concept in 1936 and when the plant closed in 1990-ish. My previous car was a black-and-chrome '69 Bug (wrecked that one), and my father also owns a restored 6-volt '63 Bug and a diesel-powered '78 VW Rabbit.

I was planning on making the frame pretty much to specs on that set of plans, but I haven't found any 5/8" tubing, so I figured I'd go for 3/4". Think I'll need a tubing notcher for the front end?
 

SpyGuy

Hooligan
Messages
406
Reaction score
1
Location
Tucson, Arizona
Okay, just ordered my CVT last night, so that should be here in a few days. The reason for the CVT instead of the standard drive right off the clutch bell:
1) it realigns the chain more towards the center of the bike - otherwise I would have to either run the chain around the frame or offest the engine towards the right to clear the frame. Either way, I would need (still need) a chainbreaker.
2) would allow me to gear the bike down without messing with an entire jackshaft setup (which I don't think my welding skills are ready for yet).

Any ideas on a small fuel tank? I was NOT thinking of locating it right on the frame between seat and forks, perhaps behind the seat on the frame. Not to worry about the exhaust - it's not going to have a standard pocketbike exhaust pipe on it, so it won't be running under the seat. I will either do the goped exhaust can, or see about doing something interesting with a busted pb pipe I have laying around .....

Also, I'm still looking around for frame material at my local Home Depot and Lowe's. I've heard 3/4" thinwall pipe should do, as well as 3/4" sch40 tubing (this is NOT conduit tubing, right?) and chromoly tubing, which I haven't been able to find yet. What do you guys think? What can I use, and where can I find it easily?

EDIT: www.mcmaster.com sells chrome-moly tubing at pretty decent prices.
 

modelengineer

Lord of the noise
Messages
1,609
Reaction score
2
Location
Sydney, Australia
You need special equipment to weld chromoly, and you need to heat treat the entire assembly after welding. It is HUGELY expensive to do.

If you can you should use an existing exhaust rather than making your own. 2-strokes make the most power with a tuned pipe, and with 50cc or so you want all the power you can crank out of that engine!
 

SpyGuy

Hooligan
Messages
406
Reaction score
1
Location
Tucson, Arizona
Actually, I've been told by a builder on another site that he uses chome-moly for his builds, and uses a small 110v MIG welder from Harbor Freight. His last project was a mini 3-wheeler pb with a custom chrome-moly framed rear end and the drive from an electric shopping cart.

Weed whacker tank ..... hmmmm. Good idea - I'll stay on the lookout for one next time I take a run to the dump. I was thinking gravity-feed, anyway.

On the 2-stroke pipe, I have a busted pb pipe, broken right at the end of the expansion chamber (mufler's gone). I was thinking of playing around with it some, seeing if I could make a short but working pipe from it. If not, I do have a spare normal pb pipe I can use.
 

SpyGuy

Hooligan
Messages
406
Reaction score
1
Location
Tucson, Arizona
Thank you for that post - very helpful. Might have to sign up on that site myself. The very last picture on the thread is exactly what I'm hoping to achieve, using a pb engine and a CVT instead of the jackshaft. Hmmm....... looks like a custom-bent exhaust for it ..... no problem, I should be able to do that.
 

SpyGuy

Hooligan
Messages
406
Reaction score
1
Location
Tucson, Arizona
*laffs* Okay, I'll try to remember not to mention the "pb" word there ..... even though some of the parts I'll be using may be from one. Got some kool stuff on that site - I may wind up building a few things.

So, chromoly tubing is pretty much the best way to go for something like this?
 

SpyGuy

Hooligan
Messages
406
Reaction score
1
Location
Tucson, Arizona
Minor update: I picked up a junked goped a little while back, mainly for the wheels and drivetrain. (Frame was cracked in several places under the deck.) The guy had left gas sitting in the 'ped for well over a year, so it had turned to shellac. EVERYTHING needed cleaning: new lines, new filter, hosed out the tank ....... finally had to go buy a new carb because the old one was so gummed up. Put everything back together, primed the carb, gave two pulls, and VROOM! So, now I think I may be using THIS engine as a powerplant instead of the pb engine. I'm also considering stealing the entire front end from it, as well: forks, wheel, front brake, and handlebars. I may keep the fold-down feature of the bars, and just chop 'em down to size. Meanwhile, I've got several more supports bolted under the deck to keep the thing rigid (for now), and took it out for a quick ride - goes pretty good! Frame's too badly damaged to save, but whatthehell, I bought it as a donor, anyway ......
 
Status
Not open for further replies.
Top