2016-02-20 (Sa) Simple Recumbent Bike Without Welding

Making a comfortable seat is going to be important. I couldn’t find much information about buying a seat for recumbent bikes, it looks like those have not been standardized like bike saddles. Yes, they’re legitimately called saddles.

One of the big differences between traditional bikes, diamond frame, and recumbent bikes is where weight is distributed. On a diamond frame the rider’s weight is on the pedals, handlebars, and the saddle. When I rode in the MS150 I learned just how much weight is put onto the seat, in fact, our team name was “No ifs, ands, sore butts, about it.” Sadly, we didn’t win the Most Creative Team Name Competition. On a recumbent bike nearly all the rider’s weight is on the seat is on the seat but fortunately the area is much greater so it is significantly more comfortable compared to a diamond frame.

I think I can keep this project under $50, so long as thrift stores are utilized, and making the seat for cheap is important. I’m not concerned if my bill goes over $50 but if I can keep the final bill of materials small and cheap I will be pleased. Salvaging existing bike parts will be one way to keep the cost low. Building from scratch is also fine but time consuming.

Spoiler: today I made a time gamble on a seat design I thought would be cool and easy to reproduce but turned out to be flimsy. Too flimsy. Unless the rider weighed 20lbs. Basically, I made a lightweight luggage rack. Bummer. Time gamble: lost. The premise was that I would make an array of parallel PVC pipes then coat them in foam, like pool noodles, and it would be a relatively comfortable seat. Had I made it out of strong materials it might work but that sounds expensive.

Enough background.
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A bolt at the junction of the bike frame and seat post was loosened and the seat and post from the youth bike was removed. The seat was removed from the post by loosening a pair of nuts on either side of the adapter.

Seat post being loosened by wrench

Bars running under the seat which connect to the adapter were measured at approximately 7mm (1/4”) diameter. 1/4-20 threaded rod was purchased to connect here. By using the existing hardware less severe modifications were necessary. Simple modifications make the project easier to copy. Standard parts do the same and this project is meant to be accessible. Threaded rods were fit into the seat post adapter and fit snugly once tightened.

1/4-20 threaded rod held in seat post hardware

Material was cut for the seat. Five lengths of PVC were cut to 16” (40cm) and four lengths of threaded rod were cut to 12” (30cm). These measurements should not have to be exact but the pieces should be uniform.

Five lengths of 16” (40cm) 3/4” PVC and four 12” (30cm) segments of threaded rod

Two lengths of the threaded rod were fastened into the seat post adapter and aligned. This ensured the rods were the correct distance apart while in use. This distance was transferred to the PVC pipes so parallel holes could be drilled.

Threaded rod segments in seat post bracket

Holes were drilled into the PVC. Pipes were held in place on a drill press by laying them in grooved piece of wood which simply ensured the drill bit would pass through the center of the pipe and the exit hole would be right across from the entry hole.

PVC drilled to fit onto threaded rod

Making threaded rods meet at 90ยบ wasn’t easy. Two angle brackets were fastened together to form each junction. One short bolt and seven nuts were necessary for each. Junction. This made for a rigid joint but it was large and costly.

Brackets made from pairs of angle braces

All the parts were assembled. Each piece of PVC was placed on the threaded rod and nuts held them in place. Nuts were not tightened securely for this phase, only snugged to keep the PVC in place. No padding was purchased since this was only to test the design. Unfortunately the seat was not rigid enough to support a person. Another method will have to be found.

Assembled seat

The rest of the posts for this project have been arranged by date.

First time here?

Completed projects from year 1.
Completed projects from year 2



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2015-12-09 (W)

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