Tom Porter's Recumbent Bike Plans - SWB versions
Tom Porter's Recumbent Bike Homebuilder Plans
This series of articles is intended to present a step by step how-to for homebuilding recumbents using text and photos. I will attempt to impart my accumulated wisdom and follies of the last 12 years.

I am Tom Porter and Ive been touring and racing my own homebuilt designs since 1992. Ive built a little over 24 bikes, mostly of various design, in that time. Ive tried just about everything but trikes and FWD rear steer. The designs Im posting are the results of many hours of trial and error, Im doing this to help others not to have to experiment so much and maybe theyll save some time. I rode DFs for 15 years before I got into recumbents but still ride a MTB in the winter (good in snow and a great reminder of why I dont go back).

Why homebuilding?
Back in the day of the 80s & 90s (nostalgia?) there were not many different designs to choose from with low dealer availability and at a higher cost than a DF with similar equipment. This led the homecrafters among us to strike out on own. Most of HBs I know were either into motorcycles, go carts, or as in my case, car racing. All sicknesses that require metalworking skills. We stick to our guns because we want something we think is a better idea and pure cussedness, and yes, we are the frugal cyclists. This can either be very costly or done on the cheap. Have the satisfaction of building your own bike and impressing all and sundry.

A word about materials
Go ahead, dream about composites or Ti, but 4130 steel is still the easiest and least time consuming and least expensive way of doing this. Steel bikes can be lightweight (and Ill stake my reputation on this). These designs should all be in the 20-24lb range depending on your purse strings. We can do this because were not concerned with the niceties of business like warranties or liabilities, but that does not mean these designs are fragile. Im a big person 64, 250lbs and have not had a failure (at least as far as recumbents are concerned). A downside is these designs wont be applicable to anyone under 510 but maybe theyll be of use to you. Go ahead and modify them if you wish and also like bungee jumping, do so at your own risk.

The designs and philosophy thereof
Ive had a revelation in 2003 thanks to the guys on Aeros about rolling resistance. So these new designs (except the touring bike) have eliminated the smaller front wheels which ride poorer anyway. Not to mention fork building issues. All three designs have a higher bottom bracket than the seat to eliminate the dreaded recumbent butt which is caused by having the bottom bracket lower than the seat causing you to sit on your gluteus maxima muscles, the pain comes from the loss of blood circulation to these and I have found that the higher BB eliminates this by forcing to sit more on your coccyx (tailbone) also this gives you a better aero profile. The three designs breakdown thusly:

The Frame Design Blueprints

700c/650c Lowracer no intermediate drive is necessary with the use of a 650c (about 25o.d) tire, triple 32/52/56 gear rings, and an 11/30 XT cassette. This gives a 27-127 gear range. I use 155 mm crank arms. The larger gear comes in handy when super street bodywork is attached. Seat height is about 14 and bottom bracket height is about 26. Being FWD the hardest bit is the front fork with a 130mm over locknut rear hub. 
Click on the drawing for a printable image
Dont fret none Ill show how this is done. The only other really difficult parts are the two pulleys, made from polyurethane. This design is a takeoff on the M5 Carbon bike of the mid 90s with the crank set moved up to clear the front tire steering lock. This bike uses the rear suspension unit.

Click on the drawing for a printable image
Dual 700c high racer this baby should have the best rolling resistance numbers around. The seat height is about 26 and the BB height is around 32, this was done to eliminate the drive side pulley in the chain line. Uses 155mm crank arm 24/42/48 with a 11/30 XT cassette, I use half step gearing for the wider range cluster. This gives a 22-118 gear range. The front fork is off the rack (yay). Also uses the rear suspension unit. This design looks similar to the Reynolds T-bone.
26/406 Touring now for something completely different. This is a fully suspended bike as I shelled out money for an air shock and fork a few years back and Im going to use em. The seat height is about 21 with about a 23 BB height, again this is to eliminate the drive side pulley. Again a 155mm crank arm, and 24/42/48 half step gearing with a 11/30 XT cassette giving a 20-107 gear range is used.

Click on the drawing for a printable image
All three designs use or could use my own design of Polyurethane suspension unit which will be the first thing to build (Ill start you out easy). 

Design Components
The designs above use a common set of components. Design blueprints and specifications are listed below.

Rear Suspension Unit
This is the rear suspension unit used by all the designs. It utilizes a polyurethane elastomer  for the bounce. After brazing the mounting brackets to the washers, the assembly is held together with a 5/16" grade 8 bolt with locknut. 

This polyurethane elastomer is available from McMaster Carr.

 

 

Click on the drawing for a printable image

Rear Stays & Pivot for FWD Designs
This drawing shows the design of the suspended rear section for the FWD designs. Oil Impregnated bronze flange bushings, which are mounted in the pivot tube, which is braised into the main frame tube, are used to provide a smooth pivoting surface.

Construction of the tubing clamps and dropouts are detailed below.

Click on the drawing for a printable image

Rear Stays & Pivot for RWD Design
This drawing shows the design of the suspended rear section for the RWD design. The RWD design has wider dropouts and a rear derailleur hanger.

Click on the drawing for a printable image

Pivot tube clamp
This drawing details the design of the pivot tube clamp. These clamps attach the pivot tube which passes through the bronze bearings that are mounted in the main frame tube to the rear suspension arms.

Click on the drawing for a printable image

Dropouts
This drawing details the design of all the dropouts used in these designs. 

Click here for a 1X printable scale drawing of the dropouts, so you can just trace them onto the sheet metal. 

Click on the drawing for a (not to scale) printable image

Main Tube Miters - High Racer & Touring
This drawing details the main tubing miters needed to build the High Racer or the Touring recumbents

Click on the drawing for a printable image

Main Tube Miters - Low Racer
This drawing details the main tubing miters needed to build the 650C-700C Low Racer recumbent. Use the HighRacer/Touring Miter drawing for the remaining joinery.

Click on the drawing for a printable image

 

More building instructions to come!

 

 

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