Search all of my sites with Google

Thursday, January 22, 2009

CrazyBike v2.0

The hardtail version I more or less came up with by accident, simply by seeing these two frames near each other when I spread all my frames out on the ground to ponder about. Again, it's just friction fit (and zip-tied) together, as a photo-mockup, to work out ideas with:

A 20" frame in front, the Magna, has the cranks down below as usual but much higher off the ground, because I have a 24" front fork in the headstock with 24" wheel. It doesn't really change the angle the fork would be at because the rear is also about the same amount higher off the ground, clamped to the down tube of the 24" Roadmaster frame.

The headstock of the Roadmaster fits over the seatpost/seattube of the Magna, in this position, and exactly aligns with it angle-wise. Because of this, it also aligns with the headstock of the Magna. That means that if I properly connect the frames so the headstock of the Roadmaster is kept empty and clears the Magna's seattube, I can use a piece of front fork steering tube inside it (already have one cut for the original recumbent [OR]) to mount the handlebars right in front of me, and not have to use absurdly-long rearward-facing ones as on the V1.0. These 'bars would hook up to a steering rod that ties to a stem mounted sideways on the front fork, and do my steering "remotely".

Since the angles of both tubes are the same, and line up from the bottom of one to the top of the other, I could also use the sprocket-and-chain method I wanted to use on the OR, but ended up not being able to due to the angle differences between my fork and my under-seat-steering tube. This would probably be even simpler to make from scrap than the tie-rod, but would probably be heavier (due to the chain).

As there are no worries about swivel and chainlength changing with the hardtail, I can more easily do the motorization, and I can incorporate many of the ideas for this I would have used for the OR, including using one drivetrain at the rear wheel for both motor and pedals, enabling me to shift gears for both, making them more efficient.

The way this drivetrain works is the cranks (on the bottom bracket of the Magna frame) have a single chainring on the LEFT side instead of the right, driving a chain that goes back to the bottom bracket of the Roadmaster frame, which will have two small chainrings from a rear cassette mounted to a shaft thru the bottom bracket shell. That shaft I've not yet decided what to make from, but most probably will be a one-piece crankshaft with the cranks cut off. The right side of that shaft will have the standard pair or trio of chainrings on it, with shifter, which will have it's chain going to the rear wheel.

The motor's belt goes thru a device explained in the next post that freewheels the belt pulley during pedalling-only modes, but otherwise passes motor power thru to a chainring, then via chain to the second of the two chainrings on that shaft described above. Thus both pedal and motor power go thru both the shiftable sets of chainrings, giving me the same range of gears for both, and the whole machine more efficient.
The motor itself hangs from the bottom of the Magna frame's rear triangle. The belt/chainring freewheel is bolted into the rear dropouts of this frame. The batteries, if I had the ones I want, would easily fit in some of the space of that rear triangle, with room for a toolkit bag, etc.

Unfortunately, since I still don't have anything of high capacity that is also even remotely small except my old nearly-useless SLAs, I may have to temporarily resort to using a pair of car batteries. :-( These could bolt in place of the cargo pods on the frame between the rear wheel and my legs, on either side of the motor system. They are VERY heavy, however, so I do not know if I can manufacture a casing that will hold them to the bike frame without damaging it--I seriously doubt either of these frames was designed to carry anywhere near that kind of load. A very small trailer just for the batteries might be necessary, but given the length of this bike is already almost a wheel longer than my Columbia, I'd really like to avoid that. If I did have to have a trailer anyway, it would allow me to expand the pair of batteries to a trio, and increase the power/speed available.

Still, even if I don't have batteries to properly run it from yet, I'm going to design this particular bike with the motor as part of it, and simply not bolt the motor on until I have a battery solution.

As long as I don't have to use the car batteries, I can also use longer cargo pods on this bike, as with CrazyBike V1.0.

The seat won't be the actual seat you see in the images, but one more like a narrow chair seat with back. There's a metal plate zip tied to the back of the seat in the images, just to show how it might appear. I'll probably make it out of wood, as that's easier to work with than any of the metal stuff I have without welding anything. If I had a pipe bender, I'd use a curved-pipe frame for the seat instead.

I'll have springs under the seat, made from a couple of saddle spring sets, because my shock-absorbing seat post is too large diameter to fit into the seattube of the Roadmaster frame. It should all mount normally to the seat tube via a standard seatpost.

No comments:

Post a Comment

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.