No announcement yet.

Engines and Bicycles

  • Filter
  • Time
  • Show
Clear All
new posts

  • Engines and Bicycles

    Hello I am in a tech class in school and I would like to do an extra project.
    Does anyone have any ideas that I could use to hook up an appriximately 4 hp engine to my 15 speed bike?
    Nothing negative please.

    Thank you very much.


  • #2
    On the factory conversions, it has a pulley that bolts to the spokes around the rear wheel. It must be a heavy wheel, heavy spokes. It works the light schwinn spokes loose.

    They have a small engine mounted over the lower tube, belt fed with idler.

    A weedeater motor would work with primary reduction and whizzer type roller drive to wheel.

    Lots of luck, beef the brakes up too..


    • #3
      I did that many years ago. I made a bracket for a three horse Briggs behind the seat that rested with a roller drive on the rear wheel. I used the left (rear) brake cable to lift the motor off the wheel, acting as a clutch. Kept the front brake. It actually worked pretty well but would go fast enough to scare me.
      Free software for calculating bolt circles and similar: Click Here


      • #4
        Check out some of the photos of early Indian motorcycles. They were just bicycles with motors.

        Myself, I would connect the motor at the bottom bracket to take advantage of excellent gearing of say, a mountain bike.

        A neat project - I have seen small steam engines used on bicycles too. All that brass sure looked shiney!

        I have also seen turbochargers converted to turbo jets and mounted on bicycles. The Swedish universities have competitions every year. (WHEEEE! Splat!)


        • #5
          When I was a teenager, I used a vertical shaft lawnmower engine moounted behind the seat. I made a wooden drive wheel which mounted on the shaft, and installed an extra sidewall (off a worn out tire) on the rim for the drive wheel to run against. The "clutch" was a lever/rope arrangement which pulled the engine toward the tire to engage the drive wheel on the extra sidewall.

          It was a real smoker off the line, but it went fast enough to make it worth the effort.
          Any products mentioned in my posts have been endorsed by their manufacturer.


          • #6
            Saw a guy on TV the other day down in Oregon. He has a small turbine engine on his bicycle. Slow off the line but it just keeps accelerating. Looked and sounded very cool. Not very good for climbing hills though, same problem that hovercraft have.

            There are some very interesting small turbines being made today, suitable for model aircraft. Only real problem is $$$$$.

            Free software for calculating bolt circles and similar: Click Here


            • #7
              one of the bozo's on one of the hydrogen peroxide rocket sites, well he mounted a cylinder and blowes 2,000 pounds of oxygen out the back in a nozzle. He has a throttle now, (gate valve) first time he had a ball valve and it blowed right out from under him.

              Sounds kinda crazy to me but if you could stop the wind resistance, well you could pedal 100 mph. (not my numbers)

              Aren't bicycles for exercise? I used to use one at Olin Chemical to get around on. Lots of big jobs have them. You ain't someone till you get a bicycle. 24vdc would be a excellent conversion too. I have a 24vdc wheelchair here, the motors should work fine.


              • #8
                Thanks, those are all great ideas.
                I am leaning towards the idea of attaching the engine to the right or left pedal (whichever is appropriate) so that the engine would do the work of pedaling and i could control the gearing system.
                Any comments/suggestions?
                Thank you.



                • #9
                  If you have a 15 Speed (triple crank, 5 speed cog I assume) why not use the motor to drive off the granny gear in front, then you still have 10 speeds to choose from. You can try to keep up with the motor as you pedal. That could be hard to do!. Take a look at tandem cranks, they have Sprockets on both sides.


                  • #10
                    Take off the pedals and cranks, having them swinging around with the motor running could really do a number on the shins! Replace the cranks with a shop made shaft that will accomidate the stock bicycle sprockets and an additional one that can be driven from a horizontal shaft engine mounted in front of and below the seat. Use a chain with centrifugal clutch to drive it. You'll have to figure out the ratio which will be pretty low (hight numerically). I doubt a 4 HP engine has anywhere near the power you can apply with your legs on the crank levers to get you moving. Your legs can't go 3600 RPM either, but a Briggs can. I would guess that attempting to obtain a speed of about 60 RPM (60:1 Ratio?)on the replacement shaft at wide open throttle would be about right. I can't imagine pedaling at much more than one revolution per second in high gear. Even that ratio might require a jack shaft or gearbox of some kind to obtain it. Some small engines have a gear reduction option available, but none that low. Otherwise you'll have a pretty big sprocket on your shop made shaft. You should still be able to shift through the gears under power with no problem sice most multi speed bicycles require that you pedal while upshifting and downshifting anyway. Thing will probably go about 80 if you have the testicles to ride it that fast.


                    • #11
                      Great project! Just a note though--Check your State and Local laws. In Texas, motor powered/assisted bicycle falls into the "Moped" class of vehicles and require a serial number, registration and TAGS! Not to mention a license.
                      Dang Cowgirls in Austin (Texas Capital) got everything fowled up.


                      • #12
                        IC engines are designed to outpt power at
                        rpm of 1000 to 3600 or so, weedeater types run a higher rpm and are geared down. People run at 40 to 120rpm, and most people have a hard time above 100rpm. Best torque will be in the 40 to 70rpm range. Use of the bicycle gearing is thus of no help as the best you can do on the low end is 1:1 or perhaps 0.7:1 ratio of pedal rpm to wheel rpm (chainwheel 22t, cassette cog 34t). At the other end the ratio is about 4:1 chainwheel 53t, cassette cog 12t).
                        IC engines will need a speed reduction of 40 to 100:1, motor input to drive output. This is the reason for using small idlers driving the tire ala Solex. The tire will have to be pretty beefy in the tread to stand up to this. Driving the Bottom bracket, the shaft the pedals/cranks attach to, will require design of a speed reduction train to couple the engine to the crank. People HP outpt is typically 0.08 to 0.3HP. Gifted, energetic types can get to 0.6hp. Lance Armstrong types do about 0.75Hp for a few hours at a time. Sprinters can develop upwards of 1.5hp for 15-30sec or so. ( Steve

                        [This message has been edited by sch (edited 09-08-2003).]


                        • #13
                          SCH has told you a lot. your 3 HP motor puts out 3 HP at the rated speed. The HP available varies from 0 HP (at idle, where if yo go slower the engine dies) to 3 HP at maybe 3600 RPM. The AVAILABLE torque (which is what you are interested in varies from 0 to some maximum at less than 3600 RPM. Again when torque goes to zero, the engine cannot overcome its own internal friction and "dies". For the reason the torque varies from zero to some maximum, your probable is gearing so the engine is producing some useful torque when you try to get the bike moving- that implies yo must have some slippage when the bike is stopped until the bike get fast enough to allow direct drive (no slippage) to the bike. The direct tire to engine scheme with a roller on the tire is the better compromise (unless you go to some clutch/ gears mechanism). So calculate how fast you wish to go at wide open throttle, and that gives you the ratio of wheel to motor speed you can use. Then if you can't start you can make a smaller motor shaft size to let you have enough torque to get the machine in motion. For sure , you do not wish to couple to the front drive sprocket, As SCH says, it must go rather slow. The engine has to be geared down by some means. And remember, the spokes, as some one else said, just cannot transfer the power to the rim. They will pull out or stretch. The old "whizzer" used a big pulley, almost as large as the wheel. this pulley was coupled to engine via a "vee" belt and a pretty small pulley on the engine. and I think the engine was only 1800 rpm max. Think it all through, keeping in mind that at low idle the engine has only enough torque to keep running- nothing to pull with- and the torque builds up as speed increases, then starts falling long before maximum HP is reached. Souped up engines usually move the maximum torque RPM up much higher than the original engine- thus the available HP goes up but the engine won't idle well (available torque at lower speeds is not enough to overcome the engines internal friction and it "dies"). So a "hot rodders" goal is to move the torque curve up so high that the HP is there but slow enough that the engine will not come apart.

                          In your case, you need low RPM torque, coupled to the wheel at a rate the you can both take off and go at a reasonable speed. That means some math before you build.


                          • #14
                            If you have chains and/or belts whizzing around under power -- make sure they have guards oever them! Getting your leg or arm pulled through a roller chain sprocket would really ruin your day.
                            Try to make a living, not a killing. -- Utah Phillips
                            Don't believe everything you know. -- Bumper sticker
                            Everybody is ignorant, only on different subjects. -- Will Rogers
                            There are lots of people who mistake their imagination for their memory. - Josh Billings
                            Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                            Don't own anything you have to feed or paint. - Hood River Blackie


                            • #15
                              If you're thinking of driving the wheel via a rubber roller against the tire, why not give this idea a try- imagine a belt sander with a rubber/fabric belt instead of sandpaper, bearing against the tire. The drive motor's roller would not be touching the tire, but would be close. The outer roller ( the front roller on the belt sander, the rear on the bicycle) would be free to be raised and lowered onto the tire, that's the clutch. There's no 'plate' for the belt to rub on, as in a belt sander, so the belt, as it's lowered onto the tire, would conform to the tire's shape, giving a contact over a much larger area than would a simple roller. This should reduce the frictional heating and tire wear, also giving a softer transition of power to the tire, probably also making less noise from the tread pattern. The belt would last considerably longer than the simple roller would, for all the same reasons just given. The motor would not need to be pivoted, and so would be more securely mounted to the frame. You are free to choose the diameter of the roller fitted to the motor, for an easily calculated 'gear ratio'. Both rollers are short, about 2 in long is all that's req'd, and the belt need not be any wider than that. The rollers are straight, no groove is needed. They would likely be made from aluminum tubing sections. The rear roller, the idler, may need to be flanged. This system would be tolerant of 'junk' in the tread, and would probably still allow a rattrap to be used, in fact, it could become part of the structure of the clutching mechanism, while serving as a support for a rain and mud deflector. I have not looked for a suitable belt, though it's a simple flat loop of maybe 2 ft length, or 1 foot, thumb to thumb.
                              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-