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Monday, April 20, 2009

New Seat Started, Building CargoPod Supports

Today I was going to just go out for a power-only jaunt to completely drain the batteries the rest of the way, and see how long it took and how fast it might go. I'd've just disconnected the pedal chain, and tucked it up out of the way. Unfortunately I didn't even get out on the street before I could detect a pretty big problem (which was not really unexpected). So my priority on what needs fixing and when got changed around for me.

The weight of the batteries is around 23 pounds each, or 46 pounds total. The way the cargo pods are mounted depends on the load they have on the bike being distributed along these lines:

  • The over-wheel rack's supports, and along the rack itself into the back of the seat's supports (which are plywood).
  • The seat's rear supports, made from an ex-front-fork off a 10-speed, which go to the same rear-dropout hardpoint at the bottom end as the over-wheel rack, and at the top end go to a large bolt thru the seat's supports, a few inches above where the rack attaches.
  • The chainstay across the bottom, which feeds both into the rear axle and the rest of the bike frame.
  • The rear axle itself, in that the side of the pods press against the axle nuts.
As you can see, the weak point is the seat supports, which I could hear groaning occasionally before, especially when I was pedalling hard trying to see how fast it would go on that canal test trip (of which there are two more videos at the end of the post). When I heard quite a creak as I backed the bike out the front door over the doorsill, I stopped and took a good look at it.

None of the photos I could take of it show the problem, as it just looks like woodgrain, but I can see cracks forming in both the supports and the seat itself, primarily around the areas near the mounting points the cargo pods are stressing. I knew I would need to change the mounting method eventually, probably soon, but had hoped it would be safe longer than this.

Since it is not, I decided that while I'm taking the back of the bike apart, I might as well also replace the seat itself with the tubing-and-mesh version I wanted to test out. I can't bend the tubing for the really good version that would be contoured like my seat is, but I can use parts of the seat I had started to build for the original recumbent idea I never finished.

Since that seat was never quite wide enough to keep me from banging shoulders on the frame anyway, I cut both top and bottom ends off, with the curved sections, so I can use them as the crossbar supports for it underneath. As they are not long enough, they will then be cut in half and the white tubes you see with multiple holes in them will be sleeved over them in the middle to extend them.

All this tubing was originally part of one of those invalid's potty chairs, which was rated for up to a 300lb person, so the tubing is pretty strong. The short white tubes were two of the adjustable feet (there should be two more but I can't find them). The silver (aluminum frame you see with them is something I was considering taking the rails from to use as seat mount slides on the bike itself, but later decided to use for cargo pod mounting instead, as you'll see. That frame was originally a medical chart rack, holding two rows of them side by side. I had altered it using the rails on there from a rackmount tower (something from Data General, I believe, found as scrap being tossed out by some repair company years and years ago) to be my music-equipment rack for taking to sci-fi conventions, where I used to play live and computer-rendered music. Two more identical rail sections were in an ex-camera flight case (huge, at least 3 feet long by two wide by a foot and a half deep) aqcuired at an auction again many years back, which I had also altered into a music-equipment rack for conventions, which also held the tower computer I used at that time.

I am still working on the seat parts, ensuring they're all fit properly before welding together, so there aren't any pics of the completed seat yet, as it probably won't be done till tomorrow at the earliest. Then I still have to make the mesh covering, and lace it on.

The new seat should weigh, with it's support brackets, about 6 pounds or so. The old one is at least 15, including it's cushions and covering. So that should help make up for the weight about to be added by the cargo pod supports.

Next up was altering some of the frame parts that needed rewelding anyway, if they were to really support the battery and cargo weight indefinitely. That white ex-fork I had used as a rear-to-front frame bottom support (running from the Schwinn's seat tube down to the dropouts on the back of the Magna frame) had only been lightly welded onto the Schwinn frame, as I had intended at some point to do this modification but had not yet gotten around to it.

This is a before pic from the front angle; you can see a lot of paint rubbed away on top of it by where the seat's supports were. The only weld to it is two small points at the seatstays on the back side, which you can't see at all in this pic.

The idea will be to cut out the entire curved section, and weld just the straight section onto the side of the seatpost itself.

Below I have cut and welded the left side, leaving the right side as-is to keep the bike's shape supported, so I don't have to brace it all to keep it straight. Without that, the only thing holding the two halves of the bike together is the seatpost joint on the Magna frame, which could swivel, if on it's own.

I cut it with the hacksaw, then shaped the end of it with a grinder and then rasps to make as close a fit to the seat tube and seatstay joins as possible, then clamped it down and welded it. It is difficult to tell, but I also moved the support's bolt-on point at the Magna's dropouts from the outside to the inside, to make room for the cargo-pod support frame.

After completing the left side, the right side was done and the barely-welded-on section removed.

It's ugly, but it is now a lot stronger than it was before, and a bit lighter (that curved section was just under a pound).

From the side there's not a lot of difference in shape, except for the part that is no longer there.

All the angles from the side remain the same. Without the seat in place, the horn is a lot easier to see. It's just clamped on the frame with a radiator hose clamp for now, until I decide if I'm keeping it there or not, at which point I will probalby weld it on to keep anyone from being stupid and stealing it.

On to the cargo pod mounts. They will also hold up separate battery boxes at some point, once I have a chance to find something suitable, or make it out of something else. Until then, the cargo pods will carry the batteries as they have so far.

First up on the pile of stuff to test-fit was a piece of bedframe I got on that windy trip to Arrowhead, and found via the Freecycle.org lists.

It was exactly long enough, but it's quite heavy, and it's also an L-shape, making it difficult to bolt the pods to, as they ride too low to seat the bottom edge into, and thus would need their own L-shape lip to mate to this one, and bolt them together. That would make them even heavier.

Next up was some durable thick-walled square tubing picked up with those big posts and lamp pole, also via the Freecycle.org lists.

Alas, it too is heavy, though I can bolt the pods directly to it's vertical outer surface. It is also a bit longer, and thus would provide more support for the part of the cargo pods that stick out beyond the rear axle.

Third and what I finally chose was the rackmount rails shown in the pic of the seat parts. They are not L- or square, but rather a...hmm. Hard-edged S, perhaps. Imagine a lowercase "h", with the leftmost lower vertical part missing, so that it doglegs down from upper left, across, then down to lower right. I should have taken a pic of the cross-section. :-)

Two of them bolted end to end, with five holes of overlap, and three bolts in those holes, is long enough to fully support the entire cargo pod length, and still reach the Magna dropout accessory hardpoint as it's front mounting point. They're a LOT lighter than either of the other options, even though they appear to be stronger, and they are definitely longer. I'm estimating each one weighs about two to three pounds; I'll weigh them before they're finally bolted on.

Because of their shape, one vertical edge (the top inside one) is bolted to the bike frame at the Magna dropout hardpoint at the front and at the Schwinn hardpoint at the rear, and the other vertical edge (the bottom outside one with all the rackmount-spaced holes) is available to bolt anything else I need to it, such as the middle-back side of the cargo pods, the battery boxes, etc.

Once I finish the seat, I will know more exactly how much space and where the space is for a top rail similar to it, if necessary, for mounting the top part of the cargo pods to.


As threatened, a couple more videos of the test ride to/on the canal. The first one is on 29th Avenue heading towards Metrocenter.
video
The second is on the CaveCreek canal bike path, just north of where Hatcher would be, I think, if it went thru there.
video

More to come as progress continues.

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