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Friday, May 22, 2009

Wheelchair-ComputerPanel Flatbed Trailer

Today I put together the basic version of the flatbed trailer, using the wheelchair main wheels and quickrelease mounts for them at the back corners of the aluminum panel, along with the wheelchair caster wheels (about 5" diameter) for the front corners. Those wheels could be replaced with larger diameter ones, and even maybe 1/2" wider, if I find a pair that are I'll probably change them out (these are pretty hard rubber, with urethane-foam "tubeless tubes" inside), so it will ride better over bumps.

They're mounted to the old mainframe-style computer front panel, which is made from aluminum a little more than 1/8" thick, folded and welded into a semi-box shape, with lips folded back around the sides about 1/2", rather than making a complete back to the "box".

So it's fairly strong. I can stand in the middle of it with the wheels attached, and wiggle around, and it rolls across the floor a bit (as it should) but it doesn't significantly bend or distort under my ~150-pound weight. I expect that with a bit of reinforcement, such as a 2x2 wooden X-frame underneath it from corner to corner, bolted to the top and sides, I'll be able to carry significant amounts of cargo on it without worry. Possibly 300+ pounds, which should be more than I will need to move at one time for the forseeable future.

Above, you can see the caster wheel mounting axle bolted to the side front corner of the panel. It is very slightly rearward-angled at the moment, and needs to be straightened. The bolt holes in the caster mount are not round, though, they're elongated. So I need to find some larger diameter bolts than the ones I have at the moment, which I can torque down harder so it can't angle like that under load. Otherwise it isn't going to keep the load on the mount/etc properly, and might damage the corner of the panel, even with the reinforcement I'm planning.

The above pic shows the rear wheel mounts, which have only half of the width of the bracket bolted to the panel's sides. The bolt holes are wider-spaced than the actual side of the panel, so I can't directly bolt both top and bottom holes to the panel. I have not yet made them, but there will be an angle-iron (aluminum, actually) bracket holding the top part of the wheel mount to the top of the panel. I still need to drill the very large hole in the bracket for the wheel's hollow quickrelease-axle-mounting bolt , so the angle-iron can be flush-mounted against the wheel mount and the top of the panel, plus find more short bolts with nuts that I can use to fasten it together securely (I have a number of long ones, but I don't want to use them on this unless I have no others). Somewhere in my salvaged stuff I'm sure I have what I need.

Because the wheels are quickrelease types, I can take them off easily to store the trailer, so it doesn't take up all that much space, unlike my other trailer which essentially takes up the same room as a very large armchair or a wheelchair.

Now, I still have to put together the hitch and towbar, which will go thru the hole in the front of the panel that was originally used for a wiring bundle, and be bolted to the top of the panel along it's length. I may use a crutch for this, as I have a number of them that are missing various pieces essential for use as crutches, but are otherwise fine, and have fairly strong tubing.

The towbar itself isn't going to need to support any vertical or lateral weight, because the front and rear wheels will support that, so the tubing only needs to be strong in tension and compression along it's length, which a crutch is great at.

The hitch itself I'm still working on, but it will go directly behind the rear wheel on the bike(s). The recumbent Crazybike2 has it's cargopod frame extending that far anyway, so I only need to install the crossmember between the ends of the two sides of the frame to mount the bike end of the hitch on.

I'm probably going to put the whole joint system on the bike, as a simple ball joint. If I use a plate with a hole in it large enough for 2/3 of a ball to stick thru, I can drill a hole in a ball of some hard material (nylon would be nice) and run a bolt thru that with a hole in the trailer end of the bolt. Then I can put that into the end of the crutch, and pin it with a cotterless pin (one of the pair I got off the baby stroller). A bungee cord around the assembly, firmly attached to the trailer and wrapped around the crossmember should make a good security mount so that even if the pin comes loose I won't lose the trailer in traffic or anything, and can just stop and re-pin it (if I carry the other pin with me in the toolkit). I can of course also just use nut-and-bolt to secure them together, but I'd rather have the quickrelease.

Then I can build a wooden frame inside the bottom of the panel, working around whatever tubing/etc is now there, to help strengthen the whole panel as a load-sharing frame.

I will put reflectors bolted to the back end and sides of the panel, and at some point I'll add lights to it. For now I can simply move my regular taillight/signals assembly to it when needed, as I used to do with the other trailer. Since this one is a lot lower to the ground, I expect it will be harder to see, especially when not loaded. When I do grocery runs, I always have a couple of large white styrofoam coolers tied down to the trailer, so on this one they should provide a lot of visibility from rear or sides. I might paint orange stripes on them just to make them a little brighter in the daytime, as I did the white stripes on the back of my recumbent cargo pods.

Since it does come apart so quickly and easily, I'll likely take it apart when I'm stopped at a destination to lock it up with the bike. If I have nothing on it, I'll run the regular bike lock cables thru it's detached wheels and panel (via one of the larger holes already in it for knobs and such, if it fits), plus around the bike. Then it will be as secure as it could be short of taking it in with me (which typically isn't allowed). If it's already loaded up, I'll just take the wheels off and cable lock them to the bike, and cable lock the trailer separately to the bike.

Unfortunately this trailer may look spiffy enough to want to steal, unlike my other one, even though it too is made of junk. Sometimes just thinking about it makes me hate people. :-(


  1. I hope you are not getting these emails as black text on black background as often seems to happen due to a bug in the assesibility program in Windows.

    I do everything in white text on black background due to poor vision.


    " Your request could not be processed. Please try again."

    That was using peview. I will try a direct post this time.

    I chose the Google ID in the drop-down menue since I have an account with them. It said that there was a problem which thwarted the post from being accepted, but that was about it.


    I thought about the tail swinging and instability, but didn't think it would be that bad with most of the weight being on the two main wheels. but your assessment makes good sense.

    Your shopping cart analogy was good. I will accept it as being potentially as bad as you judge.


    The motor I got is rated 550 RPM. If I run it to the 35 (I think) tooth chainring sprocket, that should give a maximum cadence of about 135 RPM. If I run it to the bigger 45 tooth sprocket, I get about 112 RPM max. But in the second case, I go max speed slower but with more torque from both me and the motor applied to the wheel. I have been leaning toward the second since I don't usually ride very fast and the efficiency should be higher.

    I can always try out a boost circuit to take take the voltage to a maximum of 48V instead of 24V, overcoming any lost top-end sped potential. Presently, I boost the 12V riding mower battery up to 48V and designed the circuit for doing so. I built the circuit without a printed circuit board using point to point wiring. The circuit also charges the battery, and uses the same transformer in the 12 to 48v boost circuit. It is my best design work.

    If you should like to consider doing the boost idea, too, and are proficient with solid state electronics and semiconductor theory, I have a group where circuits I composed in the free electronics simulator, LTspice are downloadable. I approve members to thwart spammers and insufficiently serious inquirerers.


    I got two of those bikes, actually I think Raleigh ones instead of Schwinn, in a matched mens' / womens' set in 24 inch frame size from Goodwill and a 26" mens' JC penny one from an old acquaintance. I'm impressed that you knew about such types already.


    Abominable about the thieving of metal and the heavy damage to lives of hard working folks out there.

    The competitive nature of people which draws them to predation causes me much grief. It is one reason I am afraid to build the new ebike project using one of those rare ten speeds.

    The neighbors' house was badly damaged by such thieves. They ripped out the copper. Grievous that they would do 20K dollars of damage for 200 dollars of metal. Cooperation all the way. Down with competition.


    I agree with the Thomas Edison quote.


    ... Re: your new trailer and other thoughts

  2. I use text-only view of emails whereever possible, so generally I don't see problems with text colors--they always show up as black text on white background, in emails.

    I suspect there was simply a server problem at that moment that kept your first post from showing up--your current post seems to have worked fine. (Note: I actually got the same message trying to preview this post, but clicking Preview again worked fine--this is one reason I compose everything in Notepad, then copy and paste to other documents. I've never had Notepad crash or lose data, so far).

    Regarding placing the casters as rear vs front, and the swinging-out of the rear during turns because of it, it might not be all that bad, but the possibility exists, and knowing my luck it would happen only at the worst possible moment, without ever happening before that in a situation I could've controlled. ;-)

    The theory is that with the wheelchair wheels being at the rear and casters at the front, the vertically-stiff towbar only pivots at the bike end (in all directions) and should be at such a level that the casters are touching the ground when the bike is level on both wheels with me sitting on it. Any cargo placed on the flatbed trailer will then be placing it's load on all four trailer wheels, to hopefully keep the load from pushing down on the bike's rear wheel and thus lifting the bike's front wheel by any amount (causing the steering problems I had with the old two-wheel trailer).

    I've considered a few possible configurations, including the first one which was two rear wheelchair wheels and the front wheel as an 8" (I think) scooter front wheel with steering tube/fork, which would have been installed "backwards" so it would act as a caster, following the steering of the bike. I may still use this method, but for now I prefer the 4-wheel version, simply because it offers more stability depending on how I load it.

    Regarding your motor, if the 550RPM is a no-load rating at 24V, keep in mind that the no-load RPM at 48V will be 1100RPM! If that's the case, you'll either need a second reduction stage or you'll need to keep your feet off the pedals, as I doubt you can keep up with 224 to 270 RPM. ;-)

    I can barely keep up with the 120-ish RPM mine is currently at, and need to gear it down or get the freewheel system in place.

    Based on my own experiences with any kind of slope or hill-climbing, I recommend you use the larger chainring for your motor receiver ring, and the smaller chainring for your pedals, so that you get more torque from either one.

    Assuming your pedal chainring set is a two-ring set, one issue you also need to check is that the chains will not intersect each other if they are both present. There may not (probably isn't) enough clearance between rings for two chains to pass each other at their intersection. This is one reason I had to move my three-ring set from the right side to the left, and lost my lowest gears by using a two-ring set on the right, with no granny-ring.

    On a three-ring set it is not an issue as you can use the granny ring for your pedals, leave the middle ring unused, and the largest for your motor.

    The boost circuit sounds very intriguing; I will email you regarding that group.

    Including you, I directly know of only two people who actually *have* a bike with one of those crankset freewheels. :-) The other is a person on the FreakBike Nation forums.

    I despise the thieves, regardless what it is they're stealing, but especially the ones taking functional things from other people that will cost a LOT to replace, destroying them, and selling them for scrap. To them, it's all just free money, but to us, it's our livelihood, and in some cases, our LIVES they are stealing and destroying!


Alternate suggestions or improvements to anything that's been posted is very welcome, and extreme detail is preferred to brevity.

Keep in mind that unless you leave an email address in your comment, I haven't any way to reply to you except to reply to your comment here. That means if you want a reply, you'll have to come back to *this* blog entry and it's comments to see my reply to you, unless you leave some method of contact within your comment.