Recently, I got a note from Maarten Janssens, you remember him, he’s the student who designed and built his own 250cc racer from scratch. Some of you commented the work he did on that project was a strong indication we might be hearing more from him and, sure enough, his first racer was just a warm up.
Maarten just turned 22, he’s still studying, but after the first bike was completed he still had an itch to build his dream bike, a bike he could race in a competitive class where prototypes were allowed, so he chose the supermono class.
There’s a lot to see in what he did here, look closely at the rear suspension, and notice the dummy tank and seat buildup, using wire mesh like John Britten. It’s a neat build.
Here’s Maarten in his own words:
The Ducati Supermono was my dream bike, but one thing that bothered me on the Ducati was that the engine was some sort of compromise with the normal v-twin crank using one of the rods as a balancer. Knowing a thing or two about KTM engines I saved up 2000euro (2500 U.S. dollars) working weekends and -sadly- selling parts from the 250RR project.
For that money I got a KTM LC4 Duke 690 engine from 2009 with only a 1000 miles on it + the injection system, wiring loom, exhaust, airbox, throttle system, clutch, radiator and fuel tank. I bought the engine with all these things because I knew I could use them or parts from them. Eventually I used a part of the inlet funnel that was attached to the airbox, I used the fuel pump from the tank, I modified the radiator and used the front pipe piece that fits into the engine. Money well spent I’d say!
Likewise for the Ohlins shock and the Showa race forks from a Ducati 998S by the way! I bought those for $350! The wheels come from the 250RR project but I’m looking for a magnesium rear wheel as I’m writing this.
Designing the frame:
1) Mass centralization: because of the position of the spring there is more room in front of the rear wheel than with a conventional system so you can put the fuel there and the spring closer to the engine so an overall gain in mass centralization is achieved. I believe mass centralization on a bike is more important than a low centre of gravity. because the fuel sits underneath the seat the total bike will be more sensitive to rider position.
2) Mass distribution: there is little difference in mass distribution between the front and rear wheel when the tank is full or empty, this makes the bike easier to ride during a race.
3) Room for the airbox: because the fuel could be moved (read above) there is more room for an airbox and electronic parts above the engine.
4) Continuously variable setting of the angle of the swing arm with the push rods: this angle has a great effect on the anti-squat effect and the weight distribution.
5) Forces: the spring forces generated by the swing arm are put onto the spring aligned with the springs axle and working from both ways. they react as negatives against each other! they don’t disturb the frame and aren’t going towards the headstock!
6) Fuel temperature: Because of the position of the fuel it will keep cooler (not closely behind the radiator or above the hot engine) and thus makes it easier to generate more power.
7) Spring adjustments: the spring is easy to reach and (dis)mount and in a couple of minutes I can change the system from progressive to linear and back.
The idea for placing the spring there formed the rest of the bike because of my belief in the advantages above.
The rest of the frame is a basic trellis frame made from 25CrMo4 seamless cold-drawn tubes. The main tubes are 25mm diameter with a wall thickness of 1.5mm. other tubes are 20×1.5mm and 14×0.8mm. More about the frame in the next point.
I had a lot of help designing the pivoting triangles the “push-rod” pushes upon. I now have the option of switching from linear suspension travel to progressive by putting the push-rods in other mounting holes. A local CNC firm made them for free for me from a solidworks file another friend helped me to make. All I did was pay for the blocks of aluminum!
Making the frame(s)
Yes, you’ve read it right! I’m not ashamed to admit I make mistakes but this was a big one! I made a new jig for this frame so I could build around the engine to ensure tight packaging. So far so good.
I started machining all the tubes and started welding them. Now that’s where it all went wrong. I never welded CrMo steel before so I thought it was just the material being a pain in the ass (sorry) during welding and I can’t say that I was content about the result but I carried on. Lucky for me I met the right friend at the right time. I didn’t make all that much parts to fit the frame yet (well I did but I don’t want to think about the old subframe, airbox an air-inlet I had to redo π He told me I used the wrong filler rod. So I chose to make a second frame.
The second frame turned out better because I had a real life example now and I could change little things that made a big difference. I also made it in a manner I thought would be better to avoid distortion due to welding.
I first built the top two “triangles” on a flat plate and connected them with the tubes that run across the frame; again on the machined steel plate. Then I connected this part with other triangles I made to fit the swingarm pivot. Last, but not least, I welded on the headstock, free from any tension of the other welds on the frame!
(Maarten wanted to be sure you knew some of the photos of his build on Facebook are of the old “bad” frame with the incorrect welds so you wouldn’t be too hard on him, but somehow, I don’t think he needed to be concerned about that. – Paul)
Making the swingarm
The swingarm eventually had to be home made so I chose to make an aluminum one that would also work as a part of the fairing. It was made from billet blocks and sheet plate I bent on my working bench. It was an unbelievable amount of work but it paid of! the pictures tell it all.
Bodywork
Since I was on a roll making everything myself again I decided to make the dummy tank/seat assembly myself too. Inspired by the John Britten documentary I bought me some $10 of wire and wallpaper glue and started on making a shape!
I had a lot of help from the guys at Polycress when making the mold. I also received a lot of support from the man behind Tyga-Europe who sponsored me with the fairing + footpegs and exhausts for the project!!
Fuel tank, airbox and subframe
They are made from alloy plate, tube, blood, sweat and yes…tears!
(current) SPECS
wheelbase: 1350mm
swingarm length (ctc): 600mm
headstock angle: 23.3ΓΒ°
fork offset: 35mm
current weight without fuel: 110kg (242 pounds) (I’m hoping to stay underneath 120kg and I think that that’s reasonable given the heavy wheels.
current horsepower: 72HP (will be tuned!)
current torque: 65Nm
——————————–
Thanks, Maarten.
(This project has been very well documented, Maarten took LOTS of photos, so choosing a few to highlight what he did was difficult. Follow the link below to see more of them.)
A photo of a finished bike draws the mind away from how it came to be there in the first place. A story like this emphasizes the process, the motivation, the skill, the determination to see it through; making mistakes and learning from them, and then, continuing on.
Many want to say they’ve built a motorcycle, to be able to point to it and look at it, however, the learning and doing isn’t always fun, it can be really hard work, so they never quite get around to it, and then we come across some builders, like Maarten, who know there’s a lot more to having a bike than wishing and dreaming, so he rolls up his sleeves and gets to work. In a few more months, when the Supermono rolls out of the shop and onto the track, if someone asks, he will be able to proudly say, “Yes, I did build that.” Very nice work, Maarten!
Link: MJ Works on Facebook
HigherRPM says
Having raced singles/supermono back in the day, this project really intrigued me. The engine choice, shock mount position and all the Γ’β¬Εin houseΓ’β¬Β fabrication were highlights in my opinion. This young man has a great future. IΓ’β¬β’m hoping for some video and commentary on its race track debut. Keep us posted Maarten. Ride onΓ’β¬Β¦..
BICHO says
I seat here….,watching the(real superduke)bike, dont know what to say…………….amazing,really exceptional concept and work!BRAVO Maarten,sei tutti noi!
Kenny says
*Long low whistle*
Wow! That looks stunning and I’m loving the attention to detail.
Respect.
Just curious but why’d you go for a dual pipe exhaust?
MJ-Works says
you need volume in the exhaust pipe with this big single engine and making one big pipe would be making a pipe that makes to much noise. That’s why there are two megaphones –> volume!
kind regards,
Maarten Janssens
MJ-Works says
Thank you for your kind words Paul! People like you (the ones that understand!) keep guys like me going!
thanks!
Taichi says
I thought a high cog was preferred over Low one? Wasn’t that why it was so counter-intuitive when Britten was doing it?
Taichi says
Sorry, that was an incomplete thought. Disregard the second sentence. Isn’t high cog better for handling? Quicker turning and less bike lean per cornering G.
I’ve don’t the math my self, calculating rotational moment as well as the angle of the center of gravity of the total system from the ground. Total system being rider and Bike, with the rider hanging off.
Miles says
Wow, I love that frame, rear spring and swingarm.
Steve says
Bravo!
Well done.
Looking forward to updates! More people should be doing this sort of thing (me included). If you look up Locost and see what can be done with donor cars, there is no reason why bikes are different in that respect.
Racetrack Style says
Excellent build. The perforated swing arm construction looks strong. Clever, too.
I like the rear shock setup. The Vyrus 600 cc Moto 2 racer had something similar but I never heard how it performed in an actual race. Congratulations so far & best of luck going forward with the racing!
Hugo says
Nice project! A similar shock arrangement was used by Yamaha on one of their older OW racebike (can’t remember which one exactly, it is in Tony Foales book) Also Ian Drysdale used a similar set-up it for his V8 bike…
A shame the shock is placed at where the leg of the rider is…making less room for the legs to tuck in. Good luck with finalising the bike…that is the most difficult part (the last 5%)
Hugo says
I found the Tony Foale page online (you must love the internet for that) it was the Yamaha OW61 racebike from 1982(!) which had that set-up
MJ-Works says
what you say about the shock being in the way of the leg is false. the shock is actually behind the knee cavity, so not in the way of the rider what so ever!
thanks for the link below by the way, was looking for that!
T-Ray says
Bravo!
Drums says
Great to see someone having a go, learning along the way, and employing some original thinking. One misconception I must correct – the Ducati Supermono engine wasn’t a compromise – a V twin with one cylinder taken off as a half assed attempt at making a single. It was actually a clever adaptation of the perfect primary balance of a 90 deg V twin to a single cylinder format. The result is one of the smoothest single cylinder engines (without balance shaft) ever produced.
Anyway, great work so far, and I look forward to seeing the finished product on the racetrack.
MJ-Works says
It does have a balancing weight instead of a balancing shaft, that is driven by the con rod that would normally move the second piston. So saying it doesn’t have a balance shaft is a bit deceiving. Don’t get me wrong, I love the ducati supermono but the engine is a combination of purpose build cases with parts from other ducati engines. Sounds like I’m negative about it but I’m not. π thanks for the kind comments on your behalf!
John Ellwood says
Very nice build. Good luck on the track Maarten.
goat kamal says
Looks like frame-building and software development are congruent: “You always throw the first one away”.
Kurt says
I’ve been watching the progress on this since the day he Maarten posted that he had received his engine for the project. I look forward to each time he posts new pix of his progress. We’ve actually discussed frame design personally, and I’m impressed by how nice of a guy he is. I cant wait to see Youtube vids of his test-n-tune sessions on the bike. It’s going to be awesome. Best of luck to him, and his fantastic looking bike. I’m sure he’ll do well.
Tom Lyons says
I think its a fine piece of work that has a lot of thought and interesting design in it.
I hope he has a lot of success and fun with it!
rohorn says
Excellent!
This is far more encouraging to see than a 1000 more Man Barbies.
Love the Locost comment above – sadly, too many perfectly good bikes are led down the aisle to the alter of style, where performance is sacrificed for fashion. Eew.
Not that Real Men disgrace themselves with that sort of poofery…
PS: reCAPTHA says “racemed” – oh yeah……
Ian Drysdale says
Very nice job Maarten, I particularly like the “cross the frame” shock position. The frame is very “business-like” as well, it looks light and strong.
I also used a “cross frame” shock position on my 750-V8 ( see website ), maybe we should form some sort of club ?
Cheers IAN
MJ-Works says
Hey Ian, I looked into your design before building mine π But honestly, the first time I had seen it was on the vyrus moto2 bike. The position just offers a lot of advantages and most of them concerning packaging. as you know offcourse!
the “shock positioned cross the frame” club π
Hugo says
This was the Yamaha system from 1982 (OW61 racebike)
http://htmlimg3.scribdassets.com/9l2pbj00cg115n3h/images/7-1ffff9bc76.jpg
Mugget says
Very awesome project, great work!!
A question about the aim for a low center of gravity… I had never thought this would be a big concern? I don’t know much about building bikes, geometry or that kind of thing, but I do know that all other things being equal, a bike with a lower CoG will require MORE lean angle for a given speed.
Or is there a point where having the CoG too high can cause problems?
David says
I remember reading somewhere as well that too low of a CoG (I think below the axle plane) cause adverse handling characteristics.
MJ-Works says
Too high or too low is never a good thing. The TU Delft university in Delft, Netherlands had build a supermono with the petrol tank underneath the engine and they said the handling wasn’t good any more.
My main point/aim in this bike is mass centralisation, not a lower centre of gravity! I thought I’d made that clear but it will be my English that doesn’t suffice.
The more the mass is centralised the easier it is to handle it. Think about a halter with weights on the ends or the weights in the middle. The latter will be easier to turn! That is what I’m trying to do with this bike. read poin 1) under “Designing the frame” again.
kind regards!
Maarten
Bart says
Generally, minimizing the polar moment around the roll axis helps a lot. Having the bike CG too far from the loaded CG slows down roll, which means the bike doesn’t tip in as well, takes more force at the bars, alll other things being equal (which they never are!)
MotoForm says
Is this Bart Terp. . . who I know ? π
This is a great project, I am working on something a bit similar at the moment.
rohorn says
If you find Supermonos interesting (And who doesn’t?), MCNSPORT 2012 TT magazine has an excellent section on 6 British Supermonos, including a KTM 690 and a homebuilt frame/swingarm/bodywork/etc… by Martin Jarvis.
I get the impression that singles racing never really took off in the US, thrived then died recently in the UK, but is still going strong elsewhere in Europe. If someone has some observations they can share, I’d love to hear them – I hope that class provides inspiration for racing projects like the MJ-Works for a long time.
It is sad that the Britten single racer never got finished…
MJ-Works says
Hey,
I sadly can’t find a copy of that magazine π sounds interesting!
More info about supermono in Europe: http://www.supermono.nl/
Maarten
rohorn says
Will copy & forward – and thanks for the link!
I’m guessing you have seen this before:
http://thekneeslider.com/archives/2008/09/29/ktm-640-lc4-single-cylinder-track-bike-project/
Homebuilt racers are my favorite (2 wheeled) subject…
Chris Walker says
Excellent work. I’d only question a few things from what I can see.
1. Why use adjustable length dogbones, when fixed length units would be lighter & using the shocks ride height adjuster would give a single point of adjustment without the differential length issues of the 2 dogbones !?
1a. Why are the shock lever pivots unbraced on their top side ? The swingarm will generate hi leverage forces through the dogbones to those pivot points, the angle is forward & up, it may work fine, but not if excessive force is applied like when landing from jumping a crest etc.
2. I hope the bottom of the petrol tank is NOT the bump stop for the swingarm, it looks close ! May crack the tank if it is !
3. The throttle body/airbox appear to be lacking bellmouths ? This will hurt max torque & thus power !
Looks brilliant, hope it goes as well as it looks.
MJ-Works says
hey some answers to your questions:
1) a shock with a ride hight adjuster would become to long and thus too wide for this kind of placement on my slim frame.
1a) If you look carefully you can see they are braced with a bar that also holds the subframe and fuel tank.
2) There is room enough π
3) specially for you: http://i.imgur.com/jnamd.jpg (not easy to take a good picture from it) I’m not that stupid that I don’t know you need a bellmouth π
thanks for wishing me good luck!
B50 Jim says
Fabulous! Extremely well thought out; good mental engineering translated into metal; great build quality. Maarten, like one of his predecessors Soichiro Honda, learns by doing and isn’t afraid to get technical help when he runs into a problem he can’t solve. My Bell’s off to him!
MJ-Works says
thank you!!
Carolynne says
Just turned 22 and already producing something this, very impressive. You have a bright future ahead
B50 Jim says
When I was 22 (in the dim, dark past) I thought I was a pretty good fabricator, making things as part of my job in factory maintenance — but this kid makes me look like a cave man at that age!
Carolynne says
I dont even want to tell you what I was doing at that age, it was a lot of fun but nowhere near this productive
B50 Jim says
Well, yeah… I was doing that, too….
MJ-Works says
Me too and I’m hoping that won’t become productive all too fast π
Carolynne says
MJ I just checked out your facebook page. I am even more impressed!!! Awesome work. How did you end up following this path so early?
B50 Jim says
WOW — just putting the Facebook page together takes a lot of work; I wonder where he finds time to build the bike? Maybe he has also discovered a way to get by without sleep!
MJ-Works says
hey Carolynne: I just love motorcycles I guess. In the article about the 250RR on the kneeslider there is a bit of my personal history I think.
B50 Jim: If you don’t make time for these things you’ll never find it. I work in the weekends, I go to school and study during the week and I have a nice girlfriend for over 6 years now that I’ll do anything for! I don’t have time I make it π
B50 Jim says
MJ — the joys of being 22! I remember it…. working during the day, rebuilding engines at night, going out on Saturday nights, taking night courses, having a love life, and not being tired at all! Enjoy it! You’ve earned it! Perhaps you could come to my house and finish remodeling the bathroom!
lmfg says
Did you FEA those bell crank mounts? They look a little thin for single sheer and off axis force input into the bell crank.
David says
Amazing project, even more for a 22 years old guy.
I am impressed, hats off!!
Kiernan says
This is awesome. I’m 30 and just dreaming of building this stuff…
I raced an NSR250 proddie bike in NZ for a few seasons in F3. Just clubracing. But out there doing laps. Got children now, so I just work…
A challenge for you: build a hossack type front end like the Britten used with your across the frame shock mount…