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Sunday, September 7, 2008

Seat Vibration Absorbers; Anti-Theft Pedals

First up is the stowable and extensible pedal tube, also removable with a quick release as an anti-theft device. If you don't have any pedals, you can't ride away with it (and it's a little heavy to carry very far).

Originally, I was just going to try calculating out the right length and angle needed for the pedal tube to put the pedals where I would be better off with them at, and weld the tube to the front headstock at whatever that came out to be, and fix it if I had to later. Then I decided it would not only be better to be able to adjust both length and angle (especially since this is my first recumbent), but that I could also set it up to be removable to make one more anti-theft device.

I decided that using the bottom bracket and the seat tube still welded to it, along with the seatpost clamp, would be the easiest way of doing it. I also left a little bit of the bottom rear tubes with the kickstand plate on the bottom bracket, so I could use it later as a mounting point for things way out front, like lights or more likely a fairing. This way I could just use a seatpost bolted or welded to a bracket of some kind on the front headstock to secure it to the bike.

I had been planning to just weld a couple of flat tabs to the front headstock above the wheel fork, so that the tube could be bolted to those. However, in staring at an old seat while cutting some other parts, I had an idea.

I could use the heavy pre-shaped rod from the bottom of one of my zillions (not really) of old seats, weld that rod to the headstock instead, and use the actual seat-mounting hardware (bolt and clamps) to secure the seatpost to the headstock.

It turned out not to be quite as easy as I'd thought, because the shaped rod is very hard to bend (so much so that it broke before bending when I tried it in a vise), so a bit of creative thought was needed. It would not sit properly against the side or front of the headstock/downtube if I used it the same way it was used in the seat itself. However, if I used the left side rod on the right side, and the right side on the left side, cutting off the entire U-piece that goes to the front narrow part of the seat, I could then easily weld at two points as shown in the pics above, and still have the jutting ends of the rods properly align and mate with the seat-mounting hardware.

Positioning it all to get it welded was a bit of a chore, but worked out ok simply using the actual seat-mounting hardware to hold the two rod pieces in the positions they needed to be in against the metal, tackwelding and then fully welding those two places per rod as shown. For good measure I also tackwelded the rods to the hardware's D-clamps (to prevent slippage), and the hardware's inner clamp for the tube itself is tackwelded to the tube, to prevent rotation of that tube during use/etc.

Now the entire pedal assembly can be stowed for easier transport inside another vehicle if necessary, or for easier parking inside a building (like inside my front room when I'm home and not out riding it), with fewer sticky-outy bits to get hurt on. :)

Here you can see it in it's extended "ride" and it's stowed positions. It can be clamped with the seat bolt to any angle in between, too, though I imagine I will probably only use it in the farthest-down position. I might alter it a bit to allow it to angle even closer to flat parallel to the ground, rather than sticking up so far, depending on how well it rides this way. The tube is shown extended about halfway down the seatpost, and could go from the six inches or so out it is now to another 3 or 4 inches out, or all the way back up against the seat mounting hardware, for either different riders or just different experimental positions.

It would probably require a shorter front chain when in the extreme close position vs the extreme extended position, since the front derailer will not take up that much slack. :) That can be made easy to change, if I'm careful about how the derailer mounts up and what order the chains go on in, to make the front chain the outer one. However, it is likely that I will have the front chain the inner one for freewheeling reasons. Not entirely sure yet, as I'm still working that out for simplest possible setup with the parts I actually have on hand.

A couple of photo updates to the previous post:

The underseat steering headstock, where the handlebars will mount and pivot from, is now welded in place. The pink fork that forms the center of the bike frame still has it's steering tube that would go inside the headstock in place, and that is positioned inside the downtube in such a way that downward pressure on the bike presses it agaist the downtube, hopefully helping to spread the stress load thru the frame forward to the front wheel better than if it was simply the edge-welds to the downtube holding it in place. I'm pretty sure the factory welds that hold the fork and steering tube together are better than my beginner's welds holding the disparate frame bits together. :-) The image is about parallel to the ground, so the angles you see should be the ride angles, more or less, plus or minus whatever changes occur with rider weight on the shocks springs.

These are a couple of closer better shots of the 24" to 20" fork modification.

The flash makes the grinding marks really stand out--they're not anywhere near as deeply grooved as they look. :-) I do need to go back over the welds again, though, because I don't think I did a good enough job there. Don't want to find that out while on the road. :-(

Since I don't have a rear shock designed and built yet (just a few good ideas and a lot of crazy ones), I just took a rusty old spring from a junk box I found in an alley and tackwelded it in place.

This will hold the frame positions about like they will be when I have an actual shock in place, so I can manipulate and guesstimate better. It doesn't actually do much springing, as it's very compressible at the angles I have everything at, though I cannot squish it by hand even a millimeter, so it's not much use beyond that.

Now, the second part: Seat Vibration Absorbers. I don't really think the shocks are going to do much about the road vibration, since they sure don't on my existing bike, and the ones on this one won't be much different in design or execution. So something to dampen the vibration to the seat is necessary. I'd like to do the same thing to the handlebars, but haven't figured out a good way to do it that won't also either make the steering potentially sloppy, or add too much complexity to the mounting point for the headstock (or force a change to some completely different steering method).

So, Roller Skate parts to the rescue. See, this is why I don't throw out the rest of something after I use what I acquired it for. :-) The wheels were very useful, even instrumental, in making the current motor drive scheme work as well as it does. But there are a lot of other nice parts on these skates, which have a rudimentary shock absorber built into the wheel mount design, with independent front and rear axle suspensions using a plastic/rubber grommet stack, thru an aluminum wheel mount/axle, bolted into the aluminum shoe plate itself. The shoes are size 7, too small by far for me, and thus donated to someone else I know that does wear that size. The lacings I kept, as they may be useful for things like lacing the seat back to the frame. The rubber stops/brakes I might use for something but I'm not sure yet what.

Below are some pics of the suspension units, of which I have four. This one doesn't show the top metal cap on the grommet stack or the nut that holds that on and compresses the stack, because I have it off to weld the nut to for an idea I need to test.

If I weld the nut to the grommet cup, I can then weld the cup to the inside end of a top tube frame piece (it happens to be a hair smaller than the inside diameter of the top tube on that red frame).

Then I can easily bolt the whole thing to that tube in such a way that I can use the ball-pivot you see there to secure the seat to, using part of the shoe brackets that contain the pivot-recess (which is filled with the same plastic as the grommets are made of, giving me a double set of vibration absorbing layers). Depending on how I do this, I might then be able to just use old innertube bands to lash the seat itself down to the suspension's axles, making it secure from coming loose with no direct metal-to-metal connections to the bike.

This is one possible way it might mount, though the ball joint actually needs to point the other way so the seat is resting on it. I'd only be cutting the ball joint section out of the shoeplate to bolt onto the side of the seatframe, to minimize the hardware sticking out.

This is another possible method that wouldn't stick out as far to the sides, but doesn't give me that second balljoint-layer of vibration resistance.

In this, I'd weld two of the wheel bearings to the seatframe, as far apart as they'd go with the nuts fully threaded on, so it wouldn't have any movement along that axle's length. The only reason for using the bearings is that I already have them, and they came off those axles and thus I know they'd fit perfectly. :-) Well, they also would provide a pivot so I could not have to worry about getting the weld angle of the axle just right.

In both of these variations, a short (6" to 8") length of that red tube would be welded at an upright and outward angle to the pink fork, just about even with the USS headstock. Exact angle is not known yet, as I have to do some measuring first to see what fits me best, and gives enough clearance for the suspended seat's laced-on bottom to clear everything below it (especially that headstock!) when I'm actually in the seat. :-)

Back to the experimenting!

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