corrado33

Hi all,
I've recently got it in my head that I want to build a weed wacker gas powered bike. However, I have a few stipulations.

• The bike should ride perfectly normal with the motor removed.
• I don't want to have to pedal when the motor is running. (I think that's dangerous.)
• The motor must have a clutch.
• Minimal modification to the bike itself.

Basically I want to use a weed wacker motor because they have a centrifugal clutch. Here's the hub question.

I would LIKE to use a flip flop hub or a hub that supports disk brakes so that I can attach the motor chain/belt to the left side of the bike, leaving the cassette and derailleur alone. Here are the questions.

1. Are flip flop hubs too wide to support a normal cassette on one side?
2. Would I be able to put a disk brake hub on my non disk brake bike? (Maybe with a bit of bending?)
3. Can I modify the disk brake hub's axle so that the hub is OUTSIDE of the frame, so I can use the biggest gear I can find?

I honestly think the disk brake hub would be the best idea, as most have threaded holes ready to accept a disk brake. I'd just have to find a gear or pulley that I can drill that hole pattern on to and I'd be golden.

The reason I don't want to simply attach it to the existing gears or chain is because I don't want to HAVE to pedal. If I run it off of a disk brake hub, the cassette will still spin freely, allowing me to coast if I'd like. I also think it's dangerous to have the pedals attached to the motor. Good way to whack your shins, hard.

mconlonx

You're asking a lot from a kludged-together system and not giving a lot of info. Also, this might not be the best forum for asking about motorized bicycles -- there's others out there and if I knew of any offhand, I'd list them.

- You can have a bike which is perfectly normal with the motor removed, but the removal and addition process could be extremely onerous and it might be a trade off, reliability vs. conversionable.
- Not sure why you think it would be dangerous to pedal with the motor running -- if the motor ever outruns you, you'll be freewheeling. I'd be more worried about the bike outrunning the motor.
- Most motors don't have a clutch, the ones which do aren't generally used for powering something needing torque like a bike.

What size of weed whacker motor? Anything below 50cc and you will be hard pressed to keep the bike up to speed without pedaling.

1. Flip flop hubs are too wide to fit much more than a 5sp freewheel. You should be thinking single-speed conversion at the same time you are doing this.
2. You should be able to fit a disk hub of some kind to your non disk bike. You need to check hub widths (OLD) to plan things out. Also, there are companies making bolt-on cogs with standard 6-bolt disk mounting holes.
3. Theoretically, you could work things out so that the drive cog is on the outside of the frame, but not without a lot of planning, machining, etc.

Mount the motor on a rear rack with a drive line down to the non drive side and see how things work out.

corrado33

Sorry, I wasn't being clear. I don't want to motor powering the pedals. If I would attach the motor to the cassette or to the existing chain (somehow), the motor would not only be powering the wheel, but also the pedals. I think THAT'S dangerous. I want my bike to be able to do both. I want to be able to pedal, but also use the motor once I get up to speed. I'll look at some bolt on cogs. I've seen a few used for motorized bikes on the google.

Honestly, now that I think about it, this isn't going to work.

I wanted to have a motorized bike which would make it easier for me to ride through various inches of snow in the wintertime. Sometimes, even in my lowest gear, it's still very hard when there's a lot of snow. But, to use a motor in that case I'd have to use a very torquey motor, not a weedwacker motor. A chainsaw motor might work, but those are harder to find. Guess I'll just have to work on my legs of steel this winter!

icepick_trotsky 

When I read the title to this thread, I thought you were constructing a weed whacker powered by pedaling. I like that idea better.

fietsbob

The ward for those afflicted with this condition were sent off to: https://www.bikeforums.net/electric-b...-bicycles.html

ThermionicScott 

+1. Posting these kinds of questions outside of that forum opens you up to being called a "lazy sod" or similar.

corrado33

Meh, people can call me what they wish, but I am by no means a lazy sod.

My intention for this bike was for it to allow me to power through heavy snowfall, not ride along on the street. Hence why I've given it up. Although there is an electric lawnmower for free on my local craigslist. I may be able to whip up an H bridge and some control circuits and have an electric bike. That'd be fun.

headloss 

+1

bicycle/pedal powered everything!!!

jgedwa

If you want to grind through snow, then maybe all you need to do is drop the gearing way down.

Even a fat bike is pretty limited though about how deep you deal with.

As someone with a fat bike, and a bike with studs and super-low gearing, I have to admit that bikes cannot solve all snow problems. Sometimes feet just work better.

Jim

mconlonx

Before I'd consider a weed whacker conversion, I'd spend dosh on a front electric motor wheel and associated controller/battery pack. With rider pedaling and electric assist up front, 2wd bike...

clengman

You could do something like this: Golden Eagle Bike Engines | Mount Kit only ? without the Engine 36 Spoke

Big drive ring that is affixed to the spokes of the rear wheel and small drive pulley on the motor would give you a decent drive reduction. You can use a motor with centrifugal clutch. If you wish to stop pedaling the rear wheel will freewheel. It won't drive the pedals.

tandempower

I thought that too. I was going to suggest a rowing-machine type setup instead as that would make it easier to position the flywheel in the horizontal position.