| Tom
Porter's Recumbent Bike Homebuilder Plans
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| 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 I’ve been touring and racing my own homebuilt designs since 1992. I’ve built a little over 24 bikes, mostly of various design, in that time. I’ve tried just about everything but trikes and FWD rear steer. The designs I’m posting are the results of many hours of trial and error, I’m doing this to help others not to have to experiment so much and maybe they’ll save some time. I rode DF’s 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 don’t go back).
Why homebuilding?
Back in the day of the 80’s & 90’s (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 HB’s 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 I’ll 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 we’re not concerned with the niceties of business like warranties or liabilities, but that does not mean these designs are fragile. I’m a big person 6’4’’, 250lbs and have not had a failure (at least as far as recumbents are concerned). A downside is these designs won’t be applicable to anyone under 5’10’’ but maybe they’ll 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
I’ve 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 25”o.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 |
| Don’t fret none I’ll 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 90”s 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 I’m
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.
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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 (I’ll start
you out easy).
Design Components
The designs above use a common set of
components. Design blueprints and specifications are listed below.
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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
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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 |
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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
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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
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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
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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 |
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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
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More building instructions to come!
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