building frankenbike

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina


Some of you might remember this bike. It is a twenty inch bike with the fork from a 26" bike installed. This bike tossed me on my butt and bruised my tailbone. I took it apart for some reason I don't remember.

I need the twenty inch rear wheel because I fall when I try to stand on one foot to swing over a big bike. I need the small crank so my legs won't hit when I try to pedal. I need the big front end so that I have a little room and the bike doesn't look so kiddie bike.

The last two bikes I built wouldn't allow for a full sized 2.125 front end. And i have had trouble with the crank being too large. So I want to use a 20" frame again with a 26" front wheel capable. I decided this time to try and extension on the front fork. Tp at least change the look of the bike if nothing else.

I decided this time to go with a simple front end extension. I couldn't weld when I built the bike above now that I can. I made two 3" extensions and I'm going to bolt and weld them onto the front fork of a 20" bike just as soon as I get to the thrift store to pick up a kids bike. If it doesn't work out I can always use the crank set and the rear wheel for parts.
 
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deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
I finished the bike too late to shoot pics but I will tomorrow. Meantime i have a question. The pedals are a little hard for me to work because My legs are too long and stiff. So I need to sit back about three or four inches. Somebody give me an idea what I can do to move that seat back.

I'm thinking a second seat post angled into the standard post. the seat should have enough tilt movement to work. Put a couple of mending pieces and drill a couple of holes then bolt and weld it.
 

Ilikeabikea

Moderator
Staff member
Jan 27, 2008
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Ptown, Texas
Deacon, I took my seat tube and made two 45 degree cuts, I made them about 2 1/2 inches apart, rotated the peices so they made two 90degree turns, welded the two seams. That made the seat end still poke straight up and moved the seat back about 2 inches. Where you make your 45 degree cuts will change the distance the seat moves back. Your welding has to be very substantial or one of the seams would be prone to breakage. Lots of leverage when you put 200 lbs of fatboy on the seat..........................
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
Deacon, I took my seat tube and made two 45 degree cuts, I made them about 2 1/2 inches apart, rotated the peices so they made two 90degree turns, welded the two seams. That made the seat end still poke straight up and moved the seat back about 2 inches. Where you make your 45 degree cuts will change the distance the seat moves back. Your welding has to be very substantial or one of the seams would be prone to breakage. Lots of leverage when you put 200 lbs of fatboy on the seat..........................
220 these days. Im creaping up. I rode it for the first time today well rode it more than in the drive and it wasn't as bad as I expected. I'm going to see if I get more sued to it. But thanks for the input. I thought about that weld problem and my lack of consistancy and decided if I do it im going to boldand weld it. It seems to be the safest way for me.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
I promised to post a picture of frankenbike so here it is....


I had just recently bought two lightweight bikes, but they won't allow for the wide front tire that I'm partial too. The Frankenbike will so I'm giving some thought to making more of this design. They are cheap enough to make for sure.

It seems that every parent bought his or her kid a 20" bike and they were outgrown after not too much use. Good ones seem to be easy to find in the thrift stores and not too expensive.

The base of this build was only 12 bucks.
 
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Rayzor

New Member
Feb 14, 2009
74
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Bako, Ca
Thats pretty nifty! does he have to pedal all the time with the elctric motor or does it run by itself some of the time?
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
It runs on electric more than half the time. It is only 250 watts if it was bigger it would do much better. I really only have to pedal to amount to anything on the really steep hills that are longer. It will climb the small ones and even the short steep one with very little help but the really steep ones or the ones that are long and moderately steep need some real pedaling.

It's a lot like my old friction bikes, it isn't so much if you need to pedal, it's mostly when you can pedal as the e-motor usually moves the bike too fast for me to catch the freewheel. One of the reasons to put it on a geared bike I expect.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
More final touches for Frankie.... I had to add a post extension to the seat. I could have bought a longer post and waited for it to arrive, but instead I rigged a 1/2" pipe nipple to the end of the seat post. It is now on the bike, I have no idea if I will even get out of the driveway with it. The extension was necessary for the pedaling. It is just too much of a strain the way it was.

I also had to make a design change to the kickstand. It somehow went over the end and dumped my bike. I welded a nut onto the bracket where the bar slipped by before. With my welding of two repairs maybe one of them will hold. My welding skills are rather hit and miss.Im resting now so that I can give the bike at least another test ride before this gorgeous day ends.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
I like frankenbike so much I built another one for my friction drive ebike. Since it was my third conversion and my second with front fork extensions I managed to get it finished in a day. Even got the friction drive motor on it.

I'm trying to decide what to do about the looks of it. I might just leave it as is for a joke. The bike has girl power and Malibu stickers with flowers. I think I might just get in touch with the female side of me. ROFL
 
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