Julian Edgar, 50, has been writing about car modification and automotive technology for nearly 25 years. He has owned cars with two, three, four, five, six and eight cylinders; single turbo, twin turbo, supercharged, diesel and hybrid electric drivelines. He lists his transport interests as turbocharging, aerodynamics, suspension design and human-powered vehicles.
A New Pedal Machine?
I’ve just returned from a week on the road.
The vehicle of choice was my recumbent pedal trike, a design that you can read more about here and here. (In the pic above I’ve just finished my ride, so explaining the wrong shoes.)
I left Gold Coast and went to Tallebudgera, Pottsville, Byron Bay, Lennox Head, Yamba and then Grafton – mostly in northern NSW. Carrying full camping gear, I stayed each night in local caravan parks, spending one night in each except at Yamba where, because of steady rain, I spent two nights.
My last stop was at Grafton, where I got picked up by car and trailer.
Including diversions, I rode about 350 kilometres.
While for ‘real’ long distance cyclists, such a distance is trivial, this is the longest pedal trip I have ever undertaken. Furthermore, in one day I rode 110 kilometres – again a laughable distance for some cyclists but a PB for me, especially when carrying 30kg of gear.
I found the trip exhilarating and rewarding. I loved being moved by my own power, working with the machine I designed and built.
The hours of pedalling also gave me plenty of time for reflection.
I think a recumbent trike with three-wheel long travel air suspension is the most comfortable way of pedal travel that is possible.
Each day I typically used 75 per cent of the suspension’s travel of about 4 inches (this was easy to judge by means of a tell-tale on the rear damper), and no matter what the surface I was riding over, the ride remained absolutely comfortable. No harshness, jerks, vibration.
And with a seat supporting an area of my body many times greater than sitting on a traditional bike seat, I never had a sore bum – or sore shoulders or sore wrists. In fact, even after my longest day, I got off the trike with only slightly sore legs.
I felt tired – certainly.
But it was an overall body tiredness rather than any specific sharp aches or pains.
But the trouble with my trike design is that it is big – and so is expensive to ship anywhere. I have sent my trike interstate but the size of the shipping crate meant the total cost was high. Sending it even further afield would be impossibly expensive – not to mention the problem of storing the crate at the other end.
So as I rode along, I started thinking of alternatives. New designs of pedal machines that would end up being more compact, and so able to be freighted long distances more cheaply. But designs that retained all the best elements of my trike.
So:
• A recumbent seat
• The same pedal axis (“bottom bracket”) height
• Air suspension with the same spring and damper rates
• Identical below-seat handlebars
• The same gearing and wheel sizes (81 gears and 20 inch wheels)
• The same anti-squat rear suspension design
And I kept coming back to a long wheelbase (LWB) recumbent bicycle with a removable seat.
The front and rear suspension arms could be designed to fold in towards the centre of the machine, and with the wheels and seat removed, the total shipping package could be potentially far smaller than the trike. The same Firestone rolling-lip air springs could be used, and – with the exception of the need to balance and the different steering – the machine would have exactly the same comfort and ‘feel’ as the trike.
Going to a bicycle design would also allow an additional two major positives – around one-third less frame and wheel mass, and – more obscurely – much reduced torsional forces to be withstood. (The latter is best understood when you think that when cornering, a bike rider shifts the centre of mass so that forces are resolved largely downwards in line with the frame. On a cornering trike, the machine tries to roll so there are torsional forces occurring, a large anti-roll bar is needed, etc.)
The major disadvantage of a bicycle is the need to balance – important at very low speeds at which a recumbent pedal machine can climb hills (no standing on the pedals is possible!). And of course, no sitting back on the seat of a stationary bike, resting as you happily munch on an apple or something.
But that last one could probably be countered by incorporating a really solid stand that supported the bike both sides.
Hmmm.
I’ve made some preliminary sketches and the machine would certainly be a long one – and so much less wieldy on tight cycle paths and the like. But then again, it would not be designed for that, but instead for long distance touring. My last experience of a recumbent bike wasn’t positive, but with this design – as with any you do yourself – I could optimise it for my preferences, so overcoming many of the aspects I disliked about that particular bike.
It would also be good fun – learning about anti-dive two wheeler suspension, the intricacies of ‘wheel flop’ and trail and castor, and developing an appropriate steering ratio.
I think I’ll do it.
on December 2nd, 2008 at 4:03 am
I’m a keen cyclists but have only ridden a recumbent bike once. Balancing is more difficult since it is harder for the rider to move their own mass around on the bike to maintain balance, as a regular cyclist does intuitively. I imagine carrying touring luggage on a rear rack would add to the difficulty, and that mounting any racks as low as possible would help, provided they don’t scrap the ground while cornering!
on December 2nd, 2008 at 11:08 am
What about a narrow track tilting trike?
http://www.bikepoint.com.au/portal/tabID__5760/ArticleID__120678/DesktopDefault.aspx
Should be lighter than the current wide track. Might even be possible to design it fold up with all three wheels concentric. No stand needed, no torsion problem, no low speed balance problem, perhaps the same high speed cornering capability? Could be a real winner if it fitted on conventional bike paths.
on December 2nd, 2008 at 11:21 am
From limited experience, short wheelbase 2-wheel recumbents seem more relaxed to ride than long wheelbase: with the front wheel underneath your legs, you can keep the tyre more easily under your CG (imagine balancing a stick with your finger). A long wheelbase, with the front wheel in front of the Bottom bracket, needs more steering input to be stable at low speeds (ie climbing). At higher speeds, all the recumbents I’ve ridden naturally tended to wander around a bit – took me some time to be comfortable with this and not fight it.
on December 2nd, 2008 at 11:26 am
Something like this but recumbent with suspension.
http://au.youtube.com/watch?v=dNAipmCKj2M
Packaging the riders legs, the cranks and a decent turning circle looks tricky. But a successful design could be commercially viable.
on December 2nd, 2008 at 11:36 am
Why not add a fairing, and electic power too? I am getting carried away?
on December 3rd, 2008 at 8:48 am
Ford Man,
Yes you are getting carried away. You’ll end up re-inventing the Sinclair C5. http://www.sinclairc5.com/
on December 3rd, 2008 at 8:12 pm
Ha ha ha…
Good point doctorpat. Scratch the fairing and electric power.
on December 4th, 2008 at 5:54 am
Even better, put small trolley wheels on the legs of the stand. That way you could use it at low speeds and for starting off and climbing, and then pull them up once you get going.
on December 4th, 2008 at 9:10 am
Actually, I wonder if a C5 would sell today (or better, 6 months ago when petrol was 50% higher). With modern batteries and some redesign of the fairing so you had weather protection….
on December 4th, 2008 at 12:09 pm
Looking forward to seeing what JE comes up with.
I’m sure he is lurking around here somewhere…..
on December 8th, 2008 at 8:15 am
http://www.abc.net.au/tv/newinventors/txt/s1122101.htm
Along the lines of what you describe
on December 10th, 2008 at 9:10 am
I would want a 200-watt 2 cycle engine fitted.Max 1.5kg
NO its NOT a motorcycle/moped, just a legal “pedal assist”.
No need to have it running all the time, just when your feeling lazy or on the Adekaide Hills etc.
Cheers,
F-0
on December 10th, 2008 at 12:22 pm
The smallest honda ‘wipper snipper’ engine is 25cc and makes a claimed 1hp. To make it legal would mean heavy throttling.
Perhaps a model aircraft engine would meet the 200w spec? But more fiddly carby setup?
on December 13th, 2008 at 8:46 pm
Hi Julian,
Did you have to increase he rear suspension pressure for the trip with all that gear? Did it affect the handling?
I ask this because I’m trying to design a 1+1 velomobile (passenger doesn’t pedal). Its primary use is one person but can carry another. I brings up some real design challenges because a light (~50) is really affected by extra load.
I’m starting to look at a separate moveable subframe for the driver and air suspension to all dynamic ride height adjustment.
on December 13th, 2008 at 9:18 pm
Yes I increased the rear air spring’s pressure.
Ride quality improved substantially because of the much higher sprung weight. Low speed handling remained excellent. Braking was much improved as the rear wheel wouldn’t lift.
However, when travelling at over say 25 km/h, the trike roll-steered which was disconcerting – ie it was twitchy. With normal loads this trait not detectable.
I think that this occurred for three reasons –
1) The higher centre of gravity caused increased roll, and any bump steer (toe changes with suspension deflection) were exacerbated. (Before I left home I should have separated the pneumatic interconnection between the two front air bags, as this would have given increased roll stiffness)
2) I reckon the rear suspension arm was torsionally twisting and so causing rear wheel steering (ie the rear wheel was adopting cambers).
3) Of course, point 1 above would contribute to point 2!
I think the Firestone airbags that I use are simply incredibly good for human powered vehicles, are easily capable of handling varying loads. In fact, I usually alter their pressure with load variations on the trike of more than about 3kg.
on December 15th, 2008 at 8:43 am
I enjoy your articles. I think that you would enjoy learning about Tom Traylor’s front wheel drive recumbent designs. You can ride and steer with both hands free to snack or whatever.
He is a long time HPV member from southern California and retired high school shop instructor. Check it out:
http://mysite.verizon.net/ts72/
Bill
on December 15th, 2008 at 7:14 pm
Bill, very timely as I spent most of today working on the new design.
Unfortunately, the cited site seems sick – pages not loading.
on December 15th, 2008 at 10:48 pm
The sight of the cited site seems fine to me. Just try it at a different time.
on December 16th, 2008 at 8:06 pm
Lots of pages still don’t open for me.
on December 16th, 2008 at 8:12 pm
Been furiously scribbling full-size in chalk on the floor.
It’s starting to look like a short wheelbase, leaning, front wheel drive, delta trike with front/rear interconnected, long travel air suspension.
Frightens me a bit – no way of testing a deisgn like this without building one.
I am about to head off to Adelaide for 3 weeks and I’ll be staying some of that time with Robert S Edgar (father), the man with numerous degrees including pure maths, engineering and arts.
I don’t think he realises the maths I’ll be asking him to do!
Perfect timing….
on December 17th, 2008 at 8:51 pm
I can’t wait to see the design!
Have a look at:
http://au.youtube.com/watch?v=fjbIAVladHs&feature=related
on December 17th, 2008 at 10:43 pm
When you say that it will be front wheel drive and delta-shaped, I have to wonder whether you’re planning on having it rear-steered as well. Although I’m sure it could be done properly in theory, rear steer has been almost universally avoided for the whole of vehicle design history on anything with a greater top speed than a forklift, presumably for a good reason. I’m imagining you basically turning the seat on your current trike through 180 degrees and I can’t see that it would be stable in corners, although I’m sure you will be able to enlighten us in the new year with an article on the design. I look forward to it!
on December 18th, 2008 at 8:07 am
Front wheel steered. It’s nothing like turning seat on current trike through 180 degrees.
on December 18th, 2008 at 8:38 am
I have a lot of respect for Paul Sims of Greenspeed. Here is his leaning, FWD, front steered, machine – http://www.greenspeed.com.au/australia/paul/images/lean4.jpg
on December 18th, 2008 at 9:52 am
Actually wave,
The fastest cars with rear-wheel steering run at about mach 1.
http://www.thrustssc.com/thrustssc/Engineering/rearster.html
on December 18th, 2008 at 10:24 am
Ah, but what is its turning circle?!
on December 18th, 2008 at 2:37 pm
Another QLD trike enthusiast has lots of interesting info here:
http://www.jetrike.com/prior-art.html
and under ‘theory’
He conciders the link between steering and leaning to be the most difficult aspect.