One pusher, different bikes?

Discussion in 'Push Trailers' started by rodar y rodar, Apr 11, 2010.

  1. rodar y rodar

    rodar y rodar New Member

    Is it feasible to do that? There are two uses I have in mind that would be nice to get some pedaling help with. Both situations are necessarilly on different bikes and I really don`t want to leave a bunch of mounts or other extra stuff permanently on either of those bikes when not using a motor, nd I REALLY can`t afford two setups, so it seems to me one pusher would be my best bet. I looked a bit through your existing threads and was kind of surprised to see that most of you seem to be dedicating one pusher to one bike, so maybe there`s a catch? Anyways, for now I`m just poking around to get some ideas. I`m currently deep into another project that I hope to finish up sometime this summer, knock wood!

  2. SimpleSimon

    SimpleSimon Active Member

    There's no reason any one pusher could not be used with any number of bikes, so long as your hitch geometry is compatible. I suppose the biggest issue is going be shifting the throttle control between bikes , but I can quite readily see a couple ways to address that easily.

    Not that I would, in all honesty. Articulated vehicles with control in the steering section and power in the pusher section have serious issues that require familiarization to use safely, and an articulated bicycle/pusher exacerbates those issues.

    If I were going to do such I'd choose to modify the old Smith Power Wheel design to make it an, in effect, articulated powered sidecar with a very close-in track on the third wheel. Could easily be done to be extremely narrow, using an old donor bike frame. The best part of that is that you no longer have a flex point along the axis of travel, the articulation is done to make it a leaner.
  3. mabman

    mabman Member

    I think you have seen my setup elsewhere online and I explained there how it can be done easily. It is best to just mount a throttle on the bikes you want to use and run the controller wires to the rear dropout and leave them there. The throttle bodies and wiring are cheap, minimal weight penalty more than made up for by the motor and makes it super easy to swap out.

    Pusher trailers do have one handling quirk that I know of, if you get on the power while the trailer is angled to the bike over 20 degrees or so say while doing a tight corner, the power will push your rear wheel around a bit but otherwise it works really well while you are under way, much better than the seatpost type hitches. The lower the hitch pivot the better it will handle. They figured that out years ago!
    Bernadi Motor Attachment-Trailer 1893.jpg
    Last edited: Apr 17, 2010
  4. rodar y rodar

    rodar y rodar New Member

    Pusher sidecar sounds very interrersting and unique, but I don`t see how it could be done in a simple or easilly removeable manner. It doesn`t mess with handling by pushing from off center more than an articulated, but on center drive wheel? Do you have a link or picture of the Smith Power Wheel anywhere? Google didn`t help at all and a site search brings up only Revo wheels, which look like a rotary engine mounted within the bike`s wheel. Sort of like an internal combustion hub motor, I guess.

    Yes, MABman- I`ve seen your setup on two other forums and I like it. It was the first example of a pusher I had ever seen or heard of and it sounded like a neat idea right from the start. Since I know that you post on both this forum and the other I asked on, I explained "over there" that it was posted in both places because it didn`t look like I was going to get any responses. I`ll probably use BOB skewers also, but build up a small flatbed for it rather than the chariot type- we`ll see how it turns out. Hopefully :)
  5. SimpleSimon

    SimpleSimon Active Member

  6. mabman

    mabman Member

    If that is what you are up to I would check in to the Xtra Wheel hitch setup in stead of the BOB perhaps? I am wanting to try it myself on the next incarnation.
  7. one pusher, different bikes

    Attached is my plan for a hitch that should work on various bikes including recumbents. I have had absolutely no problems with hitch placement at the seatpost and believe it to provide superior traction as a result of the tire to hitch angle. There is a tire loading action when the trailer pushes somewhat upward toward the hitch. That effect is lacking with a lower hitch. This has been noticed before. I believe Znsane Rider mentioned it here once.

    More importantly, the high hitch position creates a pendulum effect that leans the trailer in line with the bike as they both lean around corners. This pendulum effect does what a much heavier, stronger, closer tolerance u-joint hitch must do when a lower attachment point is chosen. The lower hitch position results in a topheavy trailer that has been seen to prompt their builders to overbuild their hitches or switch to a 2 wheeled design. The pendulum effect must be achieved by arranging for more of the trailer's weight to be below a line from the hitch to the contact point between the tire and road. The entire wheel will be above that line, so the engine must be far enough below it to compensate. Stretching the engine to wheel distance helps with this as can be seen in the second attachment.

    The higher seatpost hitch position allows the trailer to be somewhat longer and again, if the engine to wheel distance is stretched a little, the weight of the engine is close to the center of the trailer. If the trailer is not overbuilt, this allows enough flex to make a surprising difference in absorbing bumps & holes in the road. The same thing happens when a touring bicycle is built with a bit longer wheelbase and slightly relaxed frame & fork angles. The small increase in springiness greatly adds to comfort of the rider. Similarly, the first inch or two of 'suspension' in a push trailer is the most effective. Low weight on the trailer tire allows low tire pressure which gives all the added 'suspension" needed on my slightly springy trailer.

    The single wheel design is preferable in weight, narrowness, simplicity, cost and cornering stability, especially with a seatpost hitch position that increases traction, allows a lighter, less precise 'u-joint' at the hitch and adds some 'suspension' effect.

    My suggestion for a quickly removed throttle would be to use a brake lever with a clamp secured by a seatpost quick release skewer.

    The use of wingnuts and quick release clamps could allow swapping the push trailer from bike to bike with no need for tools or parts remaining on the bikes.

    Since I made the hitch drawing I have decided the best material would be HDPE (high density polyethylene) which can be found on eBay, in machine shop scrap bins or other more expensive sources.

    Attached Files:

  8. rodar y rodar

    rodar y rodar New Member

    The hitch mechanism rather than the general trailer design? It looks like Xtra uses rod where BOB has tubing and shorter pivot tube on the Xtra than BOBs, but isn`t it the same basic method?
  9. rodar y rodar

    rodar y rodar New Member

    Dennis, I see what you`re saying about lifting action due to the hitch angle and it makes sense to me. I don`t follow about the pendulum, though. Also, I can see the "line" idea in your second attatchment how moving the motor forward and the wheel back would be helpful, but I`m not so sure it`s worth the tradeoffs since it both lengthens the drive (chain, belt, or whatever) on the pusher and puts weight on the bike`s wheel and on the "bridge" of the trailer frame rather than over the trailer`s wheel. I`m sure a good bike wheel can handle a lot more than the weight of a little pusher motor, but if you build the trailer frame and gooseneck nice and stout you lose the passive suspension that you mentioned AND the long chain makes it tough for the trrailer to double as a cargo platform. Do my comments make sense?

    I like your hitch block and the idea for a seatpost QR to hold on the throttle. A few bread bag type wire ties would work great with that to keep the cable from wandering around and getting into trouble. By the way, my first "from scratch" frame is about half way done. It`s a rough copy of a V-Rex and will also be my first `bent.

    Attached Files:

  10. mabman

    mabman Member

    Yes, obviously. But it is all about the execution, not to mention the fact that BOB has a patent on their hitch and Xtra wheel does not. I like how light the Xtra hitch looks but you can make it as strong as you want by varying the diameter of the tubing used. The attachment at the axle is easy too, you just spread the loop ends over the extended axle nutz/QR's and the pressure of the hitch basically holds it in place. I would use a safety pin of some sort to keep it from ever coming loose though.

    I used a seatpost mount on a kids trail a bike in 03' with a Honda GX 31 and a Staton gear box, in fact it is still on their site somewhere I think. It worked well until you tried to turn more than 45 degrees with the power applied then it would push on the seatpost and make the bike all squirreley:sweatdrop:. The same thing happens with an axle mount but the effect is so much lower that it is way more manageable. As far as just towing goes either would work fine and do. One company even makes a rear rack mount trailer, kind of like a fifth wheel setup that they say works the best.

    Still if I was to market a pusher trailer no matter what hitch method I chose I would make a cutout at the pivot that would not allow the motor to operate after a certain degree angle like 60 or so.
  11. rodar y rodar

    rodar y rodar New Member

    If you were to market it, you`d need to watch that patent. Since I`m just thinking about a one off, I`m not concerned about it.

    X-tra Wheel hitches are tubing? They`re so small I thought it was rod! Also, I didn`t realize that they just spread. I suppose that`d do the trick, but I`ve liked the BOB system ever since I got mine and I already have skewers for both 130-135 and 145. I do like how unbulky the X-tra hitches are. Maybe a scaled down BOB fork would suit me best.
  12. Rodar; It looks like you got a great start on your recumbent. I'm eager to see its completion.

    Yes, your observations make sense. Some of it is just personal preference. I would build a cargo carrier differently, so I didn't care about the long chain.

    If you understand the benefits of keeping most of the weight below the line, then you understand what I mean by 'pendulum effect'. If the trailer can balance upright on its own due to the high hitch and low center of gravity, it will lean with the bike around a turn and won't even need a u-joint.

    In actuality my u-joint merely suppresses swaying motions that arise at certain speeds probably due to resonance amongst steering inputs, imbalance due to the heavier off axis flywheel, possible slight misalignment of tire to hitch (dogwalking) and low resistance to twisting torque in my flexy tongue etc. In my case it required only a lightweight, sloppy u-joint to tame the thing down completely. My u-joint is made from cheap, loose tolerance gate hinges. It takes a beefier, tight-tolerance hitch and twist-resistant tongue to keep a topheavy trailer upright.

    My preference is minimalism. Keep it simple, as lightweight and as easy to build as possible so more people can make one that works well. My build requires no welding.

    In my experience, whenever I had the trailer at a high angle to the bike, I was going very slowly and making such a tight u-turn that I just used the pedals instead of the engine to make the maneuver. Even though it's 4 HP, I have a 40 mph ratio so it doesn't have enough torque at low speeds to interfere with my balance when the trailer is at a high angle to the bike.

    When I initially had problems with topheaviness I solved it by extending the trailer instead of making a heavier, close-tolerance hitch and torque resistant tongue. Extra chain is inexpensive and added no complexity.

    Maybe I would have been satisfied with a shorter trailer and a stronger u-joint, but I appreciated the suspension effect I obtained with the longer trailer. The extra length reduces bumpiness due to a little flex, but also due to the fact that it doesn't lift the engine as high going over a bump as it does with a closer wheel. If the engine is directly over the wheel, the engine lifts 2 inches over a 2 inch bump. If the engine is in the middle between the hitch and tire, it lifts only 1 inch over a 2 inch bump. This may seem a minor point, but it resulted in great improvement and there is still very little tongue weight. I can ride much faster when I'm not hindered by a bouncy trailer. I didn't miss having engine weight close to the wheel for traction. It still spins rarely and only in loose gravel.

    The most stress in the 'gooseneck' part of my trailer is where the 3/4" conduit tongue pieces are bolted to the angle iron frame. A bolt hole at this stress point would reduce tubing strength too much, so use a u-bolt or j-bolt here and it will be plenty strong.

    I might not be pleased with a seatpost hitch if I had lots of low speed torque and did lots of low speed turns, but in my case it's ideal. It seems to me most are overbuilding their tongues & hitches. Due to making use of the pendulum effect I don't have to fight any significant torsion in the tongue or hitch, so two light pieces of cheap conduit work just fine and nothing needs to be welded.

    I might be forced to beef things up and use a lower hitch position if I used a torque converter but I have no use for one here in rural Illinois flatland. I feel this design could handle a 5 or even 6 HP engine as is, or at most with a couple of braces (or stouter tubing) at the lower bends in the tongue.

    Nearly everything would change if I was building a cargo carrier.

    Did you have a lot of low speed torque with your pusher?

    I just realized this is a departure from the original topic. I hope we can steer this back closer to the issue of one pusher, different bikes.
    Last edited by a moderator: May 18, 2010
  13. rodar y rodar

    rodar y rodar New Member

    "Did you have a lot of low speed torque with your pusher?"
    I don`t have one yet- have to finish my bent before I start any new projects. I don`t know how much torque I`ll end up with or how much is "a lot", but I might be in that category. I need to be able to push a load of groceries up about 800 ft or push a tandem with two riders and no cargo over a few low passes In both cases, top speed only needs to be about 15 MPH with a good portion of the power comming from the cranks.

    "I just realized this is a departure from the original topic. I hope we can steer this back closer to the issue of one pusher, different bikes."
    Haha! That`s fine by me- it did drift a little, but there`s been a lot of good information to mull over.

    I`ve been thinking about the project as well as checking out what other folks are doing and seeing what`s available and for what kind of prices. The BOB hitch really seems like the easiest interchangeability for me, especially since our tandem has a fiberglass beam rather than a stoker`s seat post. If I could talk my wife out of her Thudbuster, it would be possible to mount to the seatpost of her single instead of the tandem, but that`s a big IF right there. She loves her suspension!

    For a drivetrain, it looks like the Harbor Freight 80cc is the least expensive 4-stroke available unless I stumble into a deal somewhere. I`d prefer smaller, to keep the volme level down, but it seems only the "good stuff" is available in small versions. With that big HF motor, I could probably manage one of those Chinese CVTs. If I run into a little engine somewhere, it sounds like I pretty much need to stick with a straight ratio speed reducer- either way will keep me happy. I was thining about cargo capacity originally, but I really don`t need much. Since the bike I had in mind for that purpose has full racks, I bet I could get most of a grocery haul into my panniers. Except for 12-packs of soda- besides being heavy, those puppies really fill up a pannier in a hurry! The good point is that I usually only buy two at a time because they also fill up a pantry if I pick up too many.
  14. I was confused. It was Mabman, not you, that said he had problems with his seatpost hitch when the trailer was at an angle.
    I should have asked him if his trailer had lots of low speed torque.
  15. mabman

    mabman Member

    Yes. I was running a Honda GX31 with a 3 spd auto hub. I am happy that the other poster likes the seatpost setup but I will never use it again after switching to an axle mounting system. To each his own I guess.