Hello from central Arkansas, looking for a unique build.

Scott Smith

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Dec 28, 2019
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Hello, I’m a returning cyclist, 12 years ago I had no car, I lived in apartments in our smallish city town, (recently featured on a “TV” show woohoo) and I went everywhere on my bike I was in great shape, I had a kid hauler bike trailer, and I had baby carseat securely strapped in to the trailer, pretty much anywhere my wife and I went was on bikes with our daughter in tow.

fast forward 12 years I’ve “upgraded” everything, better vehicles, more kids, more land, more permanent residence, better(read: lower) monthly payments for housing actually (woohoo for mortgage over rent), better wife (I got full custody), and, sadly, bigger gut.

I got out my old Marin (21 speed comfort bike) the other day, put all new cables on her, all new tires and tubes, all new grips, and all new chain. Rides like the day I bought her. I rode about two miles that day and came to a realization.

If I’m going to ride this very much, and do what I had envisioned which is ride it into town, I was going to need a motor and more than 12 mph (I got up to either 20 or 25mph 12 years ago in front of one of those speed radar signs.)

Most of the bike kits I’ve seen have a separate chain that goes down to a sprocket haphazardly mounted to the left spokes. Here’s what I’d like to do, and I’d just like to know if there’s anything already on the market that does this, I’d like to have a setup where my ≈2-3 horsepower motor will constantly work in tandem with my =.2-.3 horsepower. Some sort of a, not torque multiplier, but torque “adder”. For example if the bike will do 40-45mph max with the motor I want to be able to pedal, with resistance, to add another .2 hp to maybe get 45-50 mph max, or if the bike takes say 30 seconds to accelerate to max speed of 40ish then with my pedaling it could do the same in 20 seconds or so.

I basically want the convenience of a motorized bike with the exercise of a non motor bike.

When I pedaled to 20+ mph 10 years ago I was in peak condition and I was pedaling as fast as I could so I know, without at least changing factory gearing I can’t pedal a bike to 45+mph even with motor help.

Can someone advise me, or direct me where to get advice, on what is available or throw down some ideas for multi-input torque management? I’m willing and capable of building something if anyone has any ideas.

The only idea I’ve had so far is to try putting larger pedal sprockets and smaller wheel sprockets, though if that were to work I’d have to manage throttle, clutch, brakes and making sure I’m in the right gear at any given time, which means if a chain drops off of the front sprocket or if it fails to shift and I have to make a minor adjustment to get it to shift then I could be in an awkward position at either a dangerous speed or dangerous position or both.

Ideally I’ve always envisioned something akin to a CVT set up where I could, through good gearing, match up the rpm range of the engine with the RPM range of my pedaling, feed that through a CVT to the rear wheel so that the motor is always matching my pedaling and together we build speed in the rear wheel

What do you guys think?
 

Greg58

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May 1, 2011
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Welcome to the forum Scott, 45 mph on a stock bike will be scary, 35 is scary to me. I would recommend disc brakes if high speed is your goal, side pull or v bakes are not good enough. There’s a old racers saying” it costs to go fast”, good luck.
 
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Scott Smith

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Dec 28, 2019
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Right, and I was planning on addressing that issue perhaps later on down the line, IF it even became feasible for my idea to come to fruition. The pro-shop in town sells bikes with hydraulic disc brakes and I’d definitely go that route if I could build a high speed exercise machine. I’m not wanting necessarily to increase top speed of a regular motorized kit, what I’m essentially wanting is for the motor to assist me, like I want to be pedaling like I’m going 15mph or so unassisted and get the end result of going as fast as a motor bicycle can reasonably go. If I get a motorized bicycle that I don’t have to pedal or goes faster than the pedals allow, then I’d just as soon be back on a motorcycle again.

I know if I get up to the 50-55 range I would want a longer frame, possibly more rake and trail on the forks, bigger tires to be more stable at speed. Something akin to a light motorcycle that’s not gonna blow a tire or anything. Eventually I would move on to a frame large enough to feel more comfortable and stable on the road while still being narrow enough to accommodate pedaling. I grew up in dirt bikes, and once as a joke tried to “pedal” in mid air turns out pedaling around a wide seat and tank isn’t stable even just air pedaling.
 

FOG

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Mar 3, 2019
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I'm sure the kind of bicycle gearing you're looking for is out there somewhere. I say that because I see the pro's pedaling down the alps at 50-60 mph ... while riding the top tube. That's nuts! If they don't keep their knees swinging outside their elbows there's gonna be a high speed crash.

For a motor I'd be looking at electric. Hub motors are essentially a 1 to 1 ratio with the wheel and I'm not sure how much help they'd be at elevated speeds. But with the right bicycle gears there's your exercise.

There are also mid drive electric motors that work through the pedal cranks and let you use your rear gears, but the front derailleur typically goes away. And there's the fab skills required to mount ...

With a hub motor you just need to build a wheel.

Lots of options. Research required, and this is the place to do it. Welcome to the forum.
 
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bairdco

a guy who makes cool bikes
Aug 18, 2009
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Everything you described sounds like a pedal-assist electric bike is what you need.

The basic 2 stroke kits aren't suited for going faster with pedaling. I mean, you can pedal up to speed, but once you reach the engines top speed, you're not going to get much more out of it by pedaling faster. It's just gonna be winding the motor out and would take some large pedal gearing to do it.

And you can't cut the motor at it's top speed and pedal without fighting the motors resistance.

You can buy an electric bike off the shelf to do just about everything you're asking.
 
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