Photo by Margaret Oliver
Recumbent motorcycles are nothing new, but most (all?) efforts are focused on street legal machines. Bob Horn, though, is proof there is at least one (feet) forward thinking builder, who has been working for the past half dozen years to design, build and test a recumbent racer. His persistence and dedication finally paid off when he recently lined up against conventional motorcycles in his first MRA sanctioned road races at High Plains Raceway in Colorado. In fact, these may have been the first ever sanctioned roadraces with a recumbent motorcycle in a grid filled with sport bikes.
Photo by Margaret Oliver
Bob the builder
Bob has been a builder for a long time, he built a unique Sportster powered concept back in the early 1990s, and he later built an electric powered recumbent to test some ideas about two wheel steering, but this recumbent racer project has been the focus of his efforts since 2008.
The secret motivator
Whether by design or by accident, Bob did something at the start of his project that may have contributed to its success, he wrote a post on his blog clearly outlining what he was planning to do. It’s all too easy to find an excuse for coming up short if you never publicly commit to anything, but tell everyone up front what you’re going to do and there’s a simple measure of failure and success. Either you did it or you didn’t. Unless you’re comfortable with a lifetime of excuses, you might as well get to work and make it happen.
The Workshop
The Kawasaki EXperimental500
While registering the racer at the track, Bob had to come up with a name for the bike, and though there were a lot of nicknames bandied about, the name Kawasaki EXperimental500 was chosen, a take off on the EX500 500cc twin Bob is using for power.
Here’s Bob’s list of answers to the most common questions:
- The race number has no deep meaning – it was just an available number.
- The exhaust exits out the side, not to the rear – there are no “flaming butt” issues.
- The steering axis is not parallel with the front fork – there’s a virtual pivot at the hub.
- The EX500 engine is internally stock.
- The rear swingarm, vertical link, and drum brake are temporary – a more advanced system will be installed later.
- NO street conversion or version is planned. Ever.
- NO movie replica bodwork is planned. Ever.
- The bodywork could be a lot more aerodynamic, but finished bodywork beats unfinished bodywork every time.Â
- 4 (now 6) years construction time in a garden shed at a budget of under $1.00/day.
- The donor bike cost $500.00 – the leftovers were sold for $600.00.
- Having a full time job not even remotely related to the motorsport industry, younger and older children, internet connection, lack of money, etc… didn’t stop this from getting built.
- No, I’m not giving away any design or building advice. Nor am I asking for any.
- 414Â pounds ready to ride except fuel, 50/50 weight distribution with fuel and 150 pound rider. 74 inch wheelbase. Just over 4 inches of trail.
Track time and hard lessons
Early in 2013, Bob had his first track time with the racer. The first session pointed to a few easy to remedy bugs, fixed with a carb kit and a headrest. The second session, though, was more costly as a lowside in a left turn followed by a roll in the dirt meant rebuilding the racer. Thankfully, no injuries, but there were definitely repairs to do which take time and money and a blown transmission in his van used up the race budget for 2013. Of course, that meant extra time to get things ready for the following year.
Photo by Jim Browning – Rocky Mtn Photos
Real racing
Well, the purpose of a racer is to race and in early May of 2014, Bob lined up on the grid for the first time. He was confident, but realistic. He wanted to finish, learn a lot and not be in last place at the end. He accomplished all three goals, 24th out of 25 entries. He also found he has lots of straight line speed, but his “biodegradable guidance unit” needs some tuning to master the corners, something more practice should take care of very nicely. When you’re riding a recumbent of your own design, there’s a lot of learning to do.
Photo by Margaret Oliver
In race two, a few weeks later, he placed 17th out of 18 while shaving six seconds from his lap time, it appears a little practice goes a long way. He’s starting to settle in and identify what needs to be tweaked, on the bike and with his technique. More track time may lead to some interesting battles as the season advances.
Craig Vetter has already offered a Photoshop version of what streamlining might look like on the racer which Bob says has a drag coefficient similar to farm implements, but faster corner technique might be more useful right now and the legality of streamlined bodywork in the racing world could mean it’s a moot point, unless of course, there was a separate class where rules haven’t yet been written.
Photo by Jim Browning – Rocky Mtn Photos
The beginning of something big?
Bob got a nice surprise when the Discovery Channel called and asked to make some video of his project, you’ll notice a camera mounted in some photos as a result. TV exposure could give Bob and his racer some well deserved notoriety and it could also spark efforts from other builders who, after seeing Bob take the lead, might want to jump in to this form of racing to see what they can do with it, especially if he seems to be having too much fun all by himself. If he’s competitive with conventional motorcycles, it could lead to a whole new recumbent racer series or more mixed racing with both recumbents and conventional bikes, maybe someone with an old Gurney Alligator will dust it off and get on the track, too. Who knows?
Manufacturers may be slow to sponsor this sort of racing because there’s no obvious street version they can sell, though component companies should be willing to get their name out front in what could be a new venue, but it’s tailor made for the DIY home workshop guys. I’m not sure how many hands on builders there are ready to take on a project like this when the end result is for track use only, but we might soon find out and since one of Bob’s aims with this project was to keep costs to a minimum, his success is another plus for the home builder.
Isn’t it refreshing to see something completely different? I love this whole project. He had an idea, designed it, built it and now he’s raced it. It’s taken six years so far, but I have a hunch the years going forward will be a lot more fun. Nice work, Bob! Very nice work.
Link: Rohorn.com
Link: Motorcycle Roadracing Association
Wave says
What a fantastic story! It looks like it would be great fun to ride.
There would be so much room for potential future development, I can imagine the project would be fascinating. If tyre sizes aren’t set by the racing class, it would be interesting to experiment with the effects of varying width tyres front and rear. I wonder if it would ride better with equal width tyres, or a wider one on the back?
Robert Horn says
Oh yes, it could use better tires! But the wheels it has were paid for, and the GT501s are relatively cheap and last a long time. The obvious down sides (Hah) are having less traction than the competition and my knowing that they have less traction than the competition. The next racer will have real race tires on it – and hopefully someone who knows how to use them.
Nicolas says
Excellent !
There seems to be a lot of frame/structural components on that thing, what material did you use to keep the weight low ?
Robert Horn says
Thanks!
All of the frame tubing is .083 mild steel from the local steel yard. The frame is actually very heavy (70 lbs). It should weigh at least half that, but it was cheap and easy to weld. Erring on the side of making it heavy and stiff seemed like it would be less hazardous than making it light and floppy.
Even with this engine (Close to 130 lbs), I think a properly engineered 4130 frame, modern wheels, and lighter suspension components would easily lighten it by 100 lbs without resorting to CF or Ti.
Barry Glading says
Good on MRA for making room for this sort of thing. There’s far too much control of design convention with most organisations’ class structures, so allowing Bob to race this against conventional bikes shows some very cool outside the box thinking. And good on you, Bob, for persevering.
Cheers
Barry
Decline says
Shut up and take my money! I want one!
Fantastic!
And it looks great, unlike a lot of other attempts.
Ry says
Love the story. As I always say but cant take credit for the quote ” How do you eat a elephant ? One bite at a time.”
Jim Frost says
If he finds a way to upgrade his “biodegradable guidance unit” I would love to hear about that. My bike has similar problems and could really use an upgrade too.
blackbird says
Beautiful.
Grant says
This is excellent, and it makes me want to get back into the garage and work on my own far less ambitious projects.
jon spencer says
To me the bike looks better moving than parked.
Don’t know why, though.
rfileger says
It’s tremendous that he has built his dream and that he is racing it.
It seems to me that a Hossack front suspension would be perfect
for this endeavor, rock solid, easily adjustable very predictable.
Voyager03 says
Great stuff! Good to see someone learning how to do it properly.
Track time for Feet First motorcycles is nothing new though…..
(incase you don’t see it, this is the bike in that picture from @1985
They have even been crashed
Good stuff though Rob – keep your best foot forward! 😉
Voyager03 says
Damn it! For some stupid reason I can’t post links. So that was a waste of effort.
Search for ‘Bikeweb’ – you’ll find lots of pictures of older (mostly UK based) FF’s some of them on tracks.
Voyager03 says
Oh yeah, racing rules.
Have a look at what you are allowed to do with electric racing bikes…… (and start making FFEV racers!)
Julian Bond says
Yup. Check out http://www.bikeweb.com for plenty more of this sort of thing, though not many being raced.
Julian Bond says
eg http://bikeweb.com/node/2539 A Voyager at Mallory Park during a track day.
Paul Crowe says
Bob ran his in a sanctioned roadrace, actually more than one race. That’s the difference. On track day you might find all manner of vehicles on the course, but when they line up on the grid for a real race, only official entries are allowed.
Doug says
Very refreshing to see in this age where prototype racing includes a spec tire manufacturer & soon-to-be spec ecu’s. It is also odd that the support class (to the “prototype” series) includes the same engine for every bike on the grid.
Congrats Bob. Keep building & racing.
Dave says
I know Bob mentioned he isn’t taking any building advice & the following is not advice at all, it’s just asking questions from someone who knows zilch about recumbent design & construction & is interested in learning more….
What if the engine was placed behind the rider & the foot controls were ahead of the front wheel? Would the foot controls be allowed that far out front? These questions came to mind when I noticed the length of the chain & the swing arm.
Robert Horn says
Dave,
Good question – I’m glad you asked!
There are benefits and problems with both front and rear engine layouts. I originally tried the rear engine layout on paper with this engine, but getting the weight and balance right, the rider reclined at that angle, keeping the wheelbase somewhat reasonable, keeping the front wheel out of my crotch, and getting my feet relatively close together (Which didn’t work out so well with this one after all, but could be a lot better) resulted in the current layout. I also needed to keep the steering column in the center of the bike for, well, I’ll get into that reason next year. The current chainline is temporary – it was designed around a 2 stage chain system that will make a lot more sense (And make a lot less noise!) than the current one.
Dave says
Thanks Bob. This is fascinating b/c it’s a whole new world to question everything from suspension to engine to chassis. And, that isn’t happening too much on the traditional motorcycle, particularly with suspension.
While aesthetically these are different, it’s refreshing to start thinking about this situation & the experience it offers… i.e. That top pic must have provided quite the sensation of speed !
additional questions:
1. what prohibited you from moving the motor backwards so the trans would fit at the front of your seat? (where the vertical frame spar is located). Is that vertical frame piece structural to the rest of the frame or is it more along the lines of a subframe? If the latter, could this be triangulated around the trans?…or would all of that shortening provide an un-wise, short wheelbase?
2. the swing arms are fascinating. It’s hard to tell where the rear, bottom one pivots?
thanks for pursuing this build. It opens the 2-wheeled mind that has been going with the flow for decades
Bob Horn says
Dave,
You’re right – the sensation of speed is absolutely insane. The different perspective really throws off my braking points, which means I need a lot more track time – a terrible thing, right…
Answers:
1. Yes, it could – the Gurney ‘Gator’s architecture is a very good example. BUT – for the new rear suspension, I needed about 3″ of space between me and the engine, so I used it for frame structure as well. Can’t give away the reason, yet – it should be much faster – if it works.
2. The lower rear swingarm (Probably sounds as odd to read as to write that) pivots are the rod ends bolted to the far aft bottom corners of the frame and threaded aft of the swingarm lateral member. The swingarm geometry is opposite of common practice (For more reasons that I’d rather not give away – yet), but it works very well.
Voyager03 says
Like this one?
http://www.bikeweb.com/node/2733
Bob Horn says
Yes, exactly like that! That’s a great illustration of how the rider position affects the configuration. And how good bodywork will be more streamlined than a lower rider with no bodywork.
The development potential for recumbent/FF racers is amazing….
FREEMAN says
This is a great and inspiring story. I really like your recumbent racer. Keep at it! I look forward to seeing where you go from here.
Peter Fouché says
Real racing! First you build it as you think best, then you race it. All the best Bob!
I hope my road going distant cousin looks as good when finished
http://www.bikeweb.com/node/2901
Peter
paolo tiramani says
fantastic
certainly mass centralized along a horizontal axis, wonder how it deals with fast transitions
you may want to try alternate riders as well for feedback
Peter Fouché says
If it’s like the road-going ones then the transitions will be quick. Normal riders do a double dip going into their first corner as they don’t expect to roll in so fast and they stand it up again thinking they are falling. The seat-back is a great idea as it forces you to counter-steer and makes you one with the machine.
Bob Horn says
As you guessed, It is a blast through chicanes. It rolls into – and stops rolling into – a turn with a lot less effort, but with lots of feel. The only “problem” is that, as a very responsive yet stable bike, it doesn’t compensate in any way for bad riding.
But that’s also just my opinion. The opinion of better riders would be very valuable – that should happen this season.
Voyager03 says
Fast transitions Paulo?
Have a look at the physics….. http://www.oesten-creasey.eu/hightech/feetfirs.htm
In reality you change direction REALLY FAST even with a 22 year old lardy steel framed road going ‘prototype’.
Quite seriously, I had to ride a mates Ducati Monster S4 and it felt (compared to my Voyager) to be slow steering! Other comparisons – BMW R1100RS – battleship slow turning and ’06 (rubber mounted) Harley Sportster – felt like it handled like a 1970’s dirt bike on worn knobblies. And once you are used to non-diving forks and you grab the brakes on a motorised bicycle that is still stuck with them it feels like you are going to crash. Which is presumably why so many of them do…….! 😉
paolo says
I can see the benefits for sure and I loved Royce Creasey? triangular bike in the 70’s.
you have longer a longer wheelbase and the rider is fixed ballast with a very centralized mass there are pros and cons to that
a regular bike has shorter wheel base and the rider ballast is movable in a chicane that can have some benefits on transitioning, plus in corners the ballast can move to the inside and keep the tire a little more upright, its the same issue with cruisers and Harley where you can move around much
I love the whole concept and I’d be curious to see the top speed differential between you’re bike faired and the original doner bike I bet you’d add maybe 15mph
your half formula 1 and half bike, hope to see more updates
p
Paul Blezard says
Great to see Rob’s efforts getting the publicity they deserve! FWIW, I’ve been on track with quite a variety of FFs since I raced the Difazio-Creasey at Silverstone back in 1984, and again in 1987. http://www.bikeweb.com/node/1184
I took part in the first Ecomobile world championships at Most in 1991, (and many subsequent ones)
and presented a short film about the event which can be seen here:
https://www.youtube.com/watch?v=GPZmqK5uogA
Several of us have taken a variety of Quasars around circuits too. And you can take a virtual ride with Roger Riedener around Brno in the first electric Ecomobile, back in 2008, at a goodly lick, as I had the privilege of doing for real: http://www.youtube.com/watch?v=H4J4lBIHuvs
Bob Horn says
Don’t make me come over there! On second thought…
Strong Eagle says
He needs to shorten the distance between front and rear wheels. Well known that longer bikes need more lean for an equivalent radius… get the feet positioned up near the front wheel.
Peter Fouché says
There are a lot of “well known” things – like nobody builds bikes like that. Good thing he didn’t listen.
Bob Horn says
As the turn radius increases, the effect that wheelbase has on lean angles decreases. In the pits, the racer feels like a barge – on the track, I don’t feel the steering/lean angle effects in the corners at all. In fact, the steeper steering geometry and optimised mass centralization makes it steer a lot better. The lower seat makes small shifts in rider’s weight far more effective.
The main reason why longer wheelbase motorcycles steer “Slower” is due to upward mass distribution (One’s butt might be lower on, say, choppers, but the torso and head is a lot higher), slower steering geometry, limp front ends, and limp chassis.
Paulinator says
This guy is cool!!! I love his resourcefulness. I use the same type of five-point steering linkages on a couple of hand-cycles (a three-wheeler and a two-wheeler…both front wheel steer/drive). I guess great minds think alike?
Bob Horn says
Thanks!!
Those 5 point steering systems sure are fun to work with, aren’t they! They solve an awful lot of problems…
Josh says
How does the 5 point steering work? I’m having a hard time visualizing the top half. Do the top arms form a sort of wishbone, to which the shock connects? – so that’s 3 points on the frame, but only 1 contact point on the fork..
And am I right in assuming the trail is a virtual axis from the frame-side shock mont through the center of the wheel?
Bob Horn says
The steering axis runs through the top center of the fork (Connected to the ball joint at the front of the upper A-arm) and down through the virtual pivot point defined by the two lower arms.
The axis doesn’t run through the frame side of the shock mount. Down by the hub, the axis runs just forward of the axle.
I hope that helps rather than confuses! I really ought to make a quick video of the steering system in motion. I think it is a very good racing system, but with too little steering range for the street.
Josh says
Thanks for explaining, Bob! Some pictures or a short video would really help. I hope to see more of this machine, I think it’s a fascinating concept. How limited is the steering range?
Bob Horn says
The steering range is 21 degrees on either side of center. Last I read their rules, FIM requires 15 degrees minimum and AHRMA requires 20 degrees minimum.
I’ll forward Paul a quick video of the bike’s front end in motion soon…
Josh says
Thanks so much for the time and effort to answer questions / looking forward to the video!!
FormerTurbineGuy says
Bob,
I stumbled upon your project a couple of weeks ago and it struck a chord with me. Much like some One off Rods ( sometimes it happens in the Rat Rod world ) and in Homebuilt Aircraft arena, every once and a while someone builds something that has an “Ah-Ha” moment associated with it, and you want one, Your Ex-500 has it. This is kinda like Max Balchowsky’s Old Yeller with 2 wheels. Ya gotta love American Ingenuity, doing it @ home and for low bucks and you don’t care what anyone thinks. In a world that is trying to tell us “you didn’t build that” you did build it. Outstanding Sir, you make us all want to get off our Arse’s and build something on the cheap in the garage ( or join a maker workspace ). It is time for America to “build your own stuff” especially vehicles, you never know what a catalyst you and this bike might be for others and their crazy ideas and to finally give it a try, regardless if it is a success or failure.Congrad’s Sir, they are in order!
Bob says
A hearty “Thank You!” from an ex-EAA member and Henry Gregor Felsen fan! LOVE the Old Yeller reference…
Robwrt Swift says
I draw and do a bit of conceptual design work as a hobby and I have always wanted to build a bike just like this one. except with way cooler styling. I’m designing an amphibious bike around the same sort of platform for its low center of gravity. and that suspension system lends itself well to having a rotating control arm attached to the shock to give the bike retractable wheels.my design has 2wheel drive and retractable floats/ landing gear on the sides behind the rider.
scritch says
Bob, how is your bike in a crash? It seems that you can get caught up in the handlebars instead of popping off easily.
Bob Horn says
Funny enough, I know the answer! I do tend to stay with the bike. A combination of points keep the weight of the bike entirely off of me while sliding on my side. Otherwise, the thought of being a human brake pad just sounds like a drag!
My second (Latest) crash was in the apex of the fastest long corner of the track – the initial impact and slide through the turn was otherwise very uneventful and pain free – it was the landing in the dirt after being “launched” off the edge of the track that resulted in a high enough impact to break the “Safety peg” and crush my foot between the frame and the ground. If it weren’t for that, it would have been a walk-away crash – NO injuries anywhere else!
My biggest concern is rolling the bike – further developments will protect against that.
Thanks for asking about that – I’m looking forward to a future where racing will be even more exciting for both the rider and spectator – where increased safety can result in even more intense riding!
Thomas lewis says
This would be amazing with a partially enclosed streamlined body,safer,faster and a whole lot more efficient.Also in the event of a high speed slide,you have a much better chance of walking away with all of your skin still attached.I know the feeling of your body being a brake pad,ooochh !!!!
Frits Overmars says
I just happened to stumble upon this thread and I love it.
[quote]The lower rear swingarm (Probably sounds as odd to read as to write that) pivots are the rod ends bolted to the far aft bottom corners of the frame and threaded aft of the swingarm lateral member. The swingarm geometry is opposite of common practice (For more reasons that I’d rather not give away – yet), but it works very well.
… I also needed to keep the steering column in the center of the bike for, well, I’ll get into that reason next year.[/quote]
Well, it is next year now, Bob.
The central steering column and the front and rear arms’ pivot points give the bike a nice symmetrical appearance. So when will we see the all-wheel-steered version?
Bob says
Thanks!
Work on the racer hasn’t progressed as planned. But after a few months of recovery, distractions, and, I hate to admit, some discouragement (Read “Diseases of Enthusiasm”, by Kevin Cameron…), I’m happy to say that work is really getting done. I doubt it’ll get raced this season, but it should hit the track before the year is over.
It’ll still be overweight and under-tired, but I can’t wait to see what difference the new steering system makes. That, and it is also an awful lot of fun to ride and race.
Frits Overmars says
I bet it is, Bob. But my curiosity is unstoppable. I think I figured out more or less how much positive trail you will be giving the rear wheel (assuming that the upper rear arm will remain as it is now) but how in heavens name are you going to drive a rear wheel that doesn’t even ‘steer’ around a fixed point?
Bob says
You’re right – the rear steering axis will run through the aft ball joint on the upper A-arm and through the center of the hub. The new lower swingarm is single sided (On the left) and the new upright is also single sided (On the right side). There are 2 hubs – the driven hub on the swingarm, and the steered hub on the upright, with a U-joint in the middle. The new rear wheel is another EX500 wheel with the center bored out and a new hub machined and pressed in, and a much needed brake disc added to it.
The hubs are done – just need to finish the swingarm, upright, and steering linkage hardware…
Frits Overmars says
Thank you Bob. I understand that in contrast to the moving-about virtual center of a four-bar steering system, a proper hub-center will give the rear wheel a really fixed point around which it steers, so you can drive it through a universal joint. So that answers my above question.
But what will you do up front? Keep the present set-up or switch to a hub-center?
Hub-center steering allows more steering angle, but with two-wheel steering you will need less angle per wheel. And your present four-bar system has several other charms. You can use a conventional hub; changing a wheel will be much simpler, and when steering into a corner, the front tire contact patch moves outward, so you’ll need less roll and less cornering clearance.
Pity you can’t have the rear wheel contact patch do the same; then you would need even less roll and have an even quicker reacting bike. Man, would I love to ride your contraption!
Bob says
Frits,
The front end will remain the same. The original plan was to build it as a 2WD with a front end identical to the new rear suspension, but the EX500 engine doesn’t strain the rear tire enough to justify the added weight and expense. That’ll wait for another project with a LOT more power.
The only way I could have done a racer with a 4 bar front and rear steered suspension was to build an electric one with very large hubmotors, but the unsprung weight would be intolerable. Otherwise, I think that would be the ideal arrangement. My lightweight electric bike was configured that way, but it is not likely to ever be scaled up.
I’m expecting to see a significant change in lean angles with the 2WS system – can’t wait to test (And better yet, race) it and find out if the lap times drop.
Thanks!
Frits Overmars says
Bob,
It seems we are thinking alike about steering and traction.
I was pondering about kinetic energy recovery. That would mean a hubgenerator in the front wheel (the rear wheel can’t do much braking when there is daylight between tire and tarmac) but as you say, the unsprung mass would be unacceptable.
A way out would be transmitting the front wheel drive to a sprung generator, like you are planning for your rear wheel drive.
A light two-stroke engine could be running at max.power rpm all the time from start to finish, even while braking and cornering, charging a supercapacitor, and the electric motor driving the rear wheel would make a clutch and a gearbox superfluous.
In theory the front generator could also act as a motor, driving the front wheel. But like the rear wheel that can’t contribute much to braking, the front wheel won’t be much help to acceleration when it hovers above the track.
It made me wonder if, even with a lot more power, driving your front wheel would make sense. But with your long wheelbase and low center of gravity it probably will.
Cheers,
Frits