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Wednesday, January 28, 2009

Steering Towards Testability, DIY Freewheel Remover

I finally decided on the white fork as the rear-frame-connection brace, and did a little grinding on it's former headstock-end, so I could fit it more perfectly into the triangle formed by the Roadmaster seatstays and brake bridge.

Once it fit correctly I then bolted it to the Magna frame's dropout tabs, in the little open triangle above and forward of the actual dropout slots.

After verifying the frames were aligned and centered like this, I welded the Roadmaster end of things, and left it all assembled, where it shouldn't need to be taken apart again, hopefully. At least, not until I have to break it down for storage, etc. It's very stiff, and doesn't appear to flex at all in handling. The real test will be on the road, of course.

I have been needing to remove some of the fixed-gear freewheels from smaller bike wheels for a while, but didn't have (and can't currently afford) the correct tool to do this. Since one of the more common versions I find of these freewheels is a four-position recessed-square-hole drive, I decided to take one of the wrenches I have duplicates of, and turn it into one of these tools.

I welded two tall bumps at the correct spacing, then immediately quenched it in cold water, to harden the metal more than it would be if it cooled slowly. Then I ground and filed away at the bumps until they were close enough to square to fit in the freewheel drive slots, and correctly mate the side faces together tightly. I quenched it again after the high-speed angle-grinder was used (I don't know if that makes as much difference as the quenching after welding does).

To use it, I just fit it onto the freewheel with the axle bolt still on the hub, and cover it with a large thick washer. I put the axle bolt's retainer nut on and hand-tighten down until the whole thing is snug, so the wrench can't pop out of the drive holes. Then I use it the same way as a regular freewheel remover (like the one for my Shimano style multigear freewheels), and turn it counterclockwise with the wheel rim clamped down between two pieces of wood, or if it's really tough, tap it hard with a hammer to turn it. The one in the picture didn't hardly need any coaxing, and came off pretty easily. Another one took the hammer to get off.

Now that I know the method works, I'll be making another tool similar to it to remove the 2-slot freewheels, which are a different spacing from the 4-slot ones. I have one of those right now. I also have an old Suntour multigear hub I'd like to remove from it's hub (the wheel around it wasn't even there when it was given to me, just some twisted spokes!), but it has yet another type of 2-slot drive, requiring yet another tool to be made.

I needed to find a mounting method for the motor drivetrain's rearmost chainring, which is the 60T from the old electric scooter carcass, to the pedal-axle I'm using at the Roadmaster's BB. Since I don't have any convienently-sized adapter plates already made to take the freewheel-sized hole in the chainring and convert that to the pedal-axle size, other than some larger-than-this-chainring chainrings I'd have to cut down in size, or scrap metal I'd have to lathe and drill out, I decided to just use a freewheel.

I don't actually need a freewheel in this location, but it doesn't hurt anything to have it here (other than it's small rotational mass), and the teeth conveniently line up to match the 4 bolt holes in the chainring. I'd prefer to use the actual freewheel that it came from (which has a 4-hole mounting ring integrated into it), on the old ScootNGo, but I still cannot get it off the wheel, until I make the correct freewheel remover tool. Also, the freewheel I'm using happens to have it's 4 drive-slots match up with the hex nut on the pedal-axle bolt, to allow it to drive the axle, once it's clamped in place.

On the outside (left end) of the pedal-axle, I'll have the receiver chainring for the pedal drivetrain, which I do need a freewheel for. I'd prefer it be bolted in via hole drilled in the pedal-axle and tapped for threads--unfortunately the only threads I can make are clockwise, which means that by itself, it will come unscrewed as I pedal along. So I'll have to secure it some other way, most likely by welds across the inner edge of the freewheel to the pedal axle. This means I will be damaging the freewheel in a way that makes it unusable on a regular hub again, which I don't want to do, but seems unavoidable at the moment.

Since I won't be able to tighten it down any other way, I'll use a large washer on the outer (left) side of the motor drivetrain chainring, welding the washer to the pedal axle. I'll also be welding some extra grip surfaces (just like I did with my freewheel remover) on the pedal axle's hex retainer nut to fully engage all four of the removal-drive slots. If possible, I'll do this in a way that leaves it still removable from the axle, but if not, so be it.

Last post I mentioned using a standard socket wrench's drive socket to hold the small chainring for the motor drivetrain, onto the belt-to-chainring device. This is the socket and the chainring:

They'll slip over the axle something like this:

where I have a piece of hub core tube on the left end of the axle, then the socket and the chainring slipped into it. Farther down the right are some brass-bushing/plastic spacer bits from the exercycle the chainring originally came from, which should serve to keep the chainring away from the dropout tabs, and line it up with the rear (larger) chainring. I have not yet cut the hub itself that I currently have the device assembled onto, because I am still trying to find the hub I cut apart before. I'd rather destroy as few things as possible, so I can still use them for other projects (and regular bikes) when needed. Anything that doesn't require modification is better, for that reason and because it's less work. :-)

I decided on and finished a testable version of the remote steering, via push/pull rod. Since I don't have actual Rod End Bearings available other than whatever giant ones might be in the Ford, I used 1" diameter eyehooks (salvaged some years back from someone's scrapped porch swing in an alley, I think), with washers stacked inside the hole just a bit taller than the actual eyehook, to be able to shift around a little bit during pivot, as if it were a bearing.

To make the rod itself, I simply welded the nuts for the eyehooks to thick washers, then welded the washers on each end of a small steel tube, formerly part of the handle of someone's discarded weedeater. The nut is on the inside of the tube, so it will look neater later on, after I file off the ugly extra bits of my welding job.

Then I just threaded the eyehooks thru the nuts until I had about the right distance from each part of the steering setup--the remote handlebar stem and the actual front fork stem. Each eye was bolted to it's respective pivot point as described above, and verified that the whole thing pivots as it should.

It doesn't have a huge range of motion compared to regular direct steering, but it is better than the chain steering would have been, and is both easier to fix on the road if need be, and less likely to have to do so. I haven't measured the steering angles but they are equal both left and right, and appears to be sufficient to steer normally. I get more steering range with this than the old dead Honda gas scooter has even with it's direct steering, and I doubt I will need more than this. I'll find out during testing, once I have a drivetrain working (either motor or pedals).

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