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The Kneeslider

Doers Builders and Positive People

Pulsejet Motorcycle Built for 200mph

By Paul Crowe

Bob Maddox on his jet bike
Bob Maddox on his jet bike

Over two years ago, The Kneeslider found a pulsejet powered bicycle on eBay built by Bob Maddox. Shortly after we wrote about it, everyone started writing about it, Bob Maddox got to be quite well known and customers began calling. Bob’s latest creation, actually built for a racer who wants to break 200mph, is a beauty, whimsically called the Harley Davidson SportJet. With 250 pounds of thrust, his initial tests, run before handing over to his customer, show a 0-60 of about 5 seconds.

I like homebuilt projects of all sorts, but when I look at those wheels and tires and think 200 mph, … maybe I’ll just grab some popcorn and watch.

Link: Wired

Video below:

Posted on November 12, 2010 Filed Under: Custom motorcycles, Motorcycle Builders

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Comments

  1. filthy919 says

    November 12, 2010 at 8:57 am

    pucker factor 11!

  2. B50 Jim says

    November 12, 2010 at 9:33 am

    A thing of beauty! Looks solid enough to do it. Realistically, it will need some kind of fairing to make 200; few riders have the muscle to hang on in a 200-mph wind blast. I’d love to see the video of the attempt, but I wouldn’t show it to my mom — she remembers those pulse-jet-powered V1 buzz bombs over London and says the sound they made was one of the most chilling things she heard during the war.

  3. bobert says

    November 12, 2010 at 9:34 am

    looks nice. Not gonna hit 200 mph. That requires aerodynamics and streamlining and front suspension. And a 0-60 in 5 seconds is hardly impressive.
    I cant take this as a serious performance machine. But the color is nice.

  4. Johndo says

    November 12, 2010 at 9:40 am

    What a waste of money a used ZX-14 will leave it in dust for the 0-60 and won’t be that far behind in the top speed department, and for maybe 4000$ total. What’s the point of having a heavy rocket engine in a custom made motorcycle if it ain’t faster?

  5. akaaccount says

    November 12, 2010 at 9:44 am

    Yeesh, take it easy positive people. Gotta say I agree though. Heavy, impractical, slow, shiny? Yep he wrote all that on the side of the tank.

  6. Phoebe says

    November 12, 2010 at 10:01 am

    I think it’s wonderful that there’s people out there making these pretty off the wall creations. I also doubt it will reach 200 mph, but I wouldn’t mind seeing the attempt. Also, the bike itself is really nicely made. That takes a lot of skill.

  7. FREEMAN says

    November 12, 2010 at 10:12 am

    I wouldn’t be surprised if it breaks 200 mph. A fairing would definitely help, but maybe there is already one in the works. As for acceleration, that really has nothing to do with high speed. Granted, this is a jet compared to a conventional motor, but many of the salt flat bikes and cars have to be pushed to speed because the gearing is so high. I’m sure there are numerous runs that broke 200 mph without hitting 60 under 5 seconds.

  8. Tenaya says

    November 12, 2010 at 10:13 am

    OK, so exactly what part of this bike is Harley? Other than the logo, of course.

  9. MikeC says

    November 12, 2010 at 10:14 am

    This is another classic ‘doing it because I can’ idea. Good on him. As for the 0-60 time, give your heads a shake. You are comparing a 160+hp traction motive (aka rear wheel drive) bike to a bike that simply compressed and moves air. Those of you with even a basic knowledge of physics will quickly understand that the 0-60 time through compressing air IS impressive. As for the 200+ mph – good luck hanging on…let alone keeping the bike straight/on the ground without aerodynamics.

  10. Bob Jones says

    November 12, 2010 at 1:12 pm

    Heh, I think they’re calling it a Harley just because of how loud it is.

  11. rohorn says

    November 12, 2010 at 2:08 pm

    Why does it say “Harley” on it? Simple – the better the Harley custom, the fewer the Harley parts on it. Can’t get any better than this!

  12. lostinoz says

    November 12, 2010 at 2:13 pm

    Am i the ONLY one that sees the BIGGEST problem about going 200 mph is the fact that theres no friggin BRAKES!?!?

    Yeah, im with the kneeslider with this…. extra butter on mine thanks!

  13. B50 Jim says

    November 12, 2010 at 2:37 pm

    Brakes only add weight. You don’t NEED brakes at Black Rock or Bonneville — just shut it off and coast down until you can apply your Chucky T’s to the earth. I’d love a front-row seat to this run; yes, extra butter and garlic salt, please.

  14. akumabito says

    November 12, 2010 at 2:37 pm

    @lostinoz You need brakes to go FAST?
    I always thought those were meant to slow you down! 😀

  15. Wol says

    November 12, 2010 at 3:02 pm

    While watching the video i had to laugh when he mentioned “the button for full throttle” Not exactly what you’d describe as subtle.

  16. Wol says

    November 12, 2010 at 3:13 pm

    for all of you who have asked why – watch the video and see and hear the thing run and all your questions will be answered. see him describe the mach 2 shock wave from the exhaust. this guy is the man. omg. you just have to laugh. It;s the craziest bike EVER. i love it.

  17. todd says

    November 12, 2010 at 3:33 pm

    The comparison with the ZX14 is interesting by the numbers:
    Considering the ZX gear ratios and tire size; at full song in 6th gear the ZX provides 366 pounds of thrust at the rear wheel. In first gear it manages 926 pounds of thrust…

    This should be fun regardless.

    -todd

  18. NIck5628 says

    November 12, 2010 at 4:01 pm

    Give the dude a break, he just likes building pulsejets. Its cool. If he wanted to build a performance bike with a jet engine then he wouldnt use a pulsejet.

  19. Steve says

    November 12, 2010 at 4:01 pm

    Well, if nothing else this will fuel the loud pipes save lives arguement! Sorry, couldnt help myself…

  20. Steve says

    November 12, 2010 at 4:05 pm

    Speaking of pulsejets, this guy has made a few http://aardvark.co.nz/pjet/

  21. John Ellwood says

    November 12, 2010 at 4:07 pm

    This is Mega cool. So cool that he could run it on the Flying Kilometer on Ice race in Orsa Sweden 11 March 2011 !

  22. Yeti B. says

    November 12, 2010 at 4:21 pm

    Judging by the comments here I assume most of you have never been to an NHRA event. Pro stock motorcycles routinely go 195 mph in the quarter mile with no fairings or aerodynamics to speak of and 1/3 of the riders are women. They seem to have no problems hanging on.

  23. Paulinator says

    November 12, 2010 at 4:52 pm

    The faster the gearing – the higher the ratio – the lower the rear wheel torque. A jet of air doesn’t do that much going slow…but at 200 mph it doesn’t loose anything, either. It actually starts gaining from ram-air effect. I hope the rider has a Kung-fu grip and goggles.

    The most impressive airshow performance that I ever witnesses was a jet powered ’61 Ford truck. It started off slow but the faster it went – the faster it went fast (really really fast!!!!).

  24. Boog says

    November 12, 2010 at 5:23 pm

    Well, Elmer Trett was doing 230 mph runs back in the late ’80’s and early ’90’s on an unstreamlined machine. He managed to hang on all except one time in ’96 when he was blown off at over 200 in what appeared to be a freak accident that ended his life. Elmer WAS top fuel motorcycle drag racing during his lifetime. What a loss…

  25. Mule says

    November 12, 2010 at 5:48 pm

    I wonder who the future cadaver is that’s thinks they’re gonna ride it tp 200mph?

    The fastest I’ve been is probably 160-ish, and I know what that was like with suspension and sorted handling. This this has 23’s with “Non-2000mph skins and rigid front and rear!

    Reminds me of the “Big Daddy Roth Wacky Wigwam-mobile”! Be neat to see in a show, but I wouldn’t want to witness the the rider’s demise first hand.

  26. ahog says

    November 12, 2010 at 6:51 pm

    Sounds as though the man knows rocket science but lacks in motorcycle know how.
    Looks like an Evil Knevil stunt
    Even then many observers knew it wouldn’t work properly.
    Intestinal fortitude over engineering and forethought.
    Back in the day it wasn’t when will he crash but how hard.

  27. woolyhead says

    November 12, 2010 at 10:56 pm

    Yay…….life is for living…..not racing from an armchair ! Naysayers abound these days it seems .

  28. joe says

    November 13, 2010 at 1:23 am

    Nice creation ! I hope he got the full blessing of Harley Davidson Inc before he used their name ? If he didn’t, then he’s going to get swarmed by their lawyers and they’ll try to sue him for every cent he’s got.

  29. mattg says

    November 13, 2010 at 2:17 am

    HA! That is wonderfully pointless. Well done! Strap a pair of stub wings on there and drive it off a ski jump like a V1.

  30. MarkW says

    November 13, 2010 at 7:06 am

    This guy, and his science project on steroids is my hero. I have no idea how competitive this would be as a drag bike, but I don’t think that was the point.

    Between the retro styling, the big honking tail pipes, and the fact that this thing actually works, the WOW factor is way up there. I’ll bet he had a ton of fun building this thing, and he got all of us to think.

    Speaking of rocket science, he’s got a thrust to weight ratio approaching 1, which means with someone crazy enough, they could line up to jump the school buses, and parachute down in the next county. Now how cool would that be?

  31. Wave says

    November 13, 2010 at 7:14 am

    MarkW, of course it would fly if you launched it off a ramp at full throttle. As others have mentioned, the pulsejet engine was developed to do exactly that with a deadly payload of explosives. The only problem would be that you would fly in an uncontrollable ballistic trajectory, and most probably spinning about the bike’s axis at a dizzying rate. With a parachute and a suitably daredevil rider it could be done, but I don’t think the authorities would allow it. Stunts these days are designed and calculated to the extent that backflipping a Harley is essentially safer than crossing the street on foot.

  32. Tom says

    November 13, 2010 at 7:22 am

    I’m a high speed bike racing know NOTHING. But yeh, the 0–60 mph? For a pulsejet, that IS impressive. Remember guys, they’re going for a top speed of 200mph. Not joining a drag race. He’ll get there with those motors. Well, as long as the bike holds together/ doesn’t plough into the ground.

  33. John S says

    November 13, 2010 at 12:11 pm

    “And a 0-60 in 5 seconds is hardly impressive.”

    True, but the 60-200 in the next 5 seconds will be… I think the limiting factor is an inability to carry more than 10 seconds of fuel.

  34. tim says

    November 13, 2010 at 4:33 pm

    Am I right in thinking there’s not throttle: so you turn it on, hope for the best, maybe hit 200mph then, what? turn the fuel off and coast to a stop? If the leathers dont start brown, they’ll be brown at the end, betcha!

  35. tim says

    November 13, 2010 at 4:42 pm

    the other thing that is a bit scary is the riding position. His feet are waaaay out wide, directly under the seat, with the big lean forward to the bars. That strikes me as interesting. Now I want to see it run.

  36. Bjorn says

    November 14, 2010 at 7:24 am

    Thank Dog for Bob Maddox; any idiot with $4K can have a ZX-14. We are richer as a community of motorcyclists, for having people like Bob building bikes like these.

  37. Mule says

    November 14, 2010 at 12:00 pm

    Bjorn,
    I agree! I feel so much richer and safer because a guy had the courage and energy to build a brakeless, suspension-less bike that happens to be jet powered and capable of who know what top speeds (maybe 200mph?). The world is now a better place.

  38. todd says

    November 14, 2010 at 6:14 pm

    Well, in order to reach 200 mph with 250 pounds of thrust he would need to have a frontal area of 5 square feet (a ZX-12 is 6) and a drag coefficient of 0.4 (motorcycles with fairings are 0.6). So, yes, he will need streamlining to get drag down low. If he could get it down to the typical 0.6 with a fairing he would need about 360 pounds of thrust. You can easily see how critical aerodynamics are at those speeds.

    With 5 square feet of frontal area, and a 0.6 Cd he could get to 177 mph with 250 pounds of thrust. That’s the speed equivalent of a similar sized motorcycle with 130 HP or a 160 HP normal sized motorcycle.

    MarkW, don’t forget there’s a rider. With a light jocky the combination will be around 400 pounds, too much for the 250 pounds of thrust to lift vertically.

    -todd

  39. smithmotorwheel says

    November 14, 2010 at 8:25 pm

    I don’t care if it is practical or sensible; it’s still cool to see. I appreciate the skill and engineering to build it regardless whether or not it can break 200 safely. I’d rather see something like this than a street tracker, bobber, chopper or other type of ‘formula’ bike.

  40. Mule says

    November 14, 2010 at 9:03 pm

    I spend a lot of time looking at Rodder’s Journal and recently picked up the reprint compilation book of Throttle magazine. It existed for one year only and then disappeared after 12-07-1941. The editor went off to war. Anyway, these mags/book have huge amounts of space devoted to the early days on the dry lakes doing land speed attempts. In those early days, a lot of drivers got cleaned out learning all the lessons about basic safety stuff related to car/bike construction and protective gear that have evolved into what we consider to be common knowledge or at the least, good sense. Tossing all that out the window to make something retro or cool puts the rider in this case, all the way back to the wrong side of trial by fire. Not the place to be when we’ve come so far. Just my opinion. Cool loses all its romance when you’re sliding trapped under a bike 187mph. But it looks like the builder does nice work craftsmanship-wise.

  41. Bjorn says

    November 15, 2010 at 12:24 am

    While I wouldn’t choose to stick that fuel injected hand grenade between my legs, I wouldn’t tell anyone except my kids (who I’m legally responsible for) not to.
    As the sarcastic Mule says, “In those early days, a lot of drivers got cleaned out learning all the lessons about basic safety stuff related to car/bike construction and protective gear that have evolved into what we consider to be common knowledge or at the least, good sense.” It’s all common knowledge. If someone chooses to ignore all that and have a go, that is their choice. That’s what freedom of choice is all about, going your own way as long as it doesn’t hurt others. It’s not like humans are an endangered species.

  42. Scotduke says

    November 15, 2010 at 7:08 am

    This thing looks nuts, and I like it. Streamlining would certainly help achieve its top speed potential at Bonneville. Is it really a Harley? Will it really top 200mph? I’m not really bothered about either of those questions. The fact is, it exists and it’s an interesting example of motorcycle engineering. I wouldn’t want to ride it myself but I applaud the builder for his creation and his creativity. There may be more practical ways to go fast but so what?

    It isn’t a rocket, it’s a pulsejet.

  43. Paulinator says

    November 15, 2010 at 10:23 am

    Hey Todd,

    Can you recommend a good link or two for doing those calcs? I want to figure out how fast a GY6-based Morgan will go. (…or maybe “how slow” is a better choice of words). The stock 150cc engines make about 8 or 9 hp, but mine is thundering out about 12 or 14 hp.

  44. Jay Allen says

    November 15, 2010 at 11:17 am

    Where are the negative comment police today? Oh wait, it’s Harley bashing, all is well.
    Congrats to his creativity and thinking outside the box. Remember some lunatic put a steam engine on a bicycle back in 1869 . . . .
    Great comments from Bjorn, Mule

  45. Nicolas says

    November 15, 2010 at 12:54 pm

    there is probably not 1% of the folks commenting on this site who’d have the imagination, drive, talent, skills and corones to build and ride a bike like this one. I’m not part of this 1%, so I shut up, I appreciate the art and wish Bob all possible success on his V1 on wheels …

    Popcorn is not appropriate, you need to bring sausage links and steaks to grill out of the exhaust of the beast.

    Stun gun as spark plug … that’s awesome

  46. Mule says

    November 15, 2010 at 12:57 pm

    Maybe I’m all screwed up! Wouldn’t be the first time.

    Burt Munro went to Bonneville with no suspension and marginal brakes, although he was fully streamlined which if done correctly can add huge amounts of stability. I know in the movie he had big wiggles initially, but I’m not sure of the true story. Maybe I should read more!

    Love, “A sarcastic Mule”

  47. B50 Jim says

    November 15, 2010 at 1:49 pm

    Burt Munro had wiggles, oscillations, heebee-jeebees and every other thing that can happen on the high side of 150, yet he somehow held on. He did indeed lose his goggles on that first run so he was riding mostly blind. Contrary to the movie he never topped 200 but that’s a moot point. What’s important is that he was there, trying his heart out. He went back to Bonneville year after year until the Reaper stopped his efforts.

  48. rohorn says

    November 15, 2010 at 1:51 pm

    I was wondering when someone would point out how many “straightline” bikes have no suspension.

    Then there’s the fact that most straightline bikes put up with a LOT of rear tire slip – something a pulsejet wouldn’t have to deal with. I can’t remember the rear contact patch speed vs front on salt flat/dry lakebed/dry pavement is atwell over 150mph, but it is amazingly high. Eliminating that does wonders for high speed stability – and generating speed.

    Oh yes – “ram air” does wonders for pulse jets in that speed range somewhere between static and supersonic.

    I just wonder what sort of speed those tires can handle.

  49. Mule says

    November 15, 2010 at 2:22 pm

    A thought on the traction of wheel-driven vs jet driven. Jet cars at bonneville LOOK like jets and have big downforcre built in so they don’t get airborne. This thing, if the Ram effect kicks in at say 150 and the thing really takes off, one wheel or the other would tend to get very light. Meaning the thing wants to bury the front wheel into the salt (or dry lake dirt) or would try to take off like a plane. Either way, most likely the pilot will become disattached from an accelerating vehicle. Without suspension to obsorb some of the either subtle or violent weight transfer, I predict passenger discomfort of biblical proportions. Wouldn’t the Munro bike be static, based on proper set-up (and many returned visits to Bonneville) regardless of speed, with the exception of fairing down-f or lift providing what was deemed to be needed?

    I say all this with the assumption that this is a serious effort and not a “Potential 200mph showbike”. If that’s what this is, I guess all this functional discussion isn’t relevant and I should say, “Man, wow it’s really cool!”

  50. todd says

    November 15, 2010 at 3:09 pm

    Paulinator, this is good reference for what it takes to go fast on the salt:
    http://www.rbracing-rsr.com/aerohpcalc.html

    -todd

  51. B50 Jim says

    November 15, 2010 at 3:54 pm

    The one factor not included in the calculations is the coefficient of ‘nads required by the rider, which increases with the cube of the speed.

  52. B50 Jim says

    November 15, 2010 at 4:18 pm

    One more comment — Have you noticed that the more outlandish (yes, even crazy) the machines posted, the more commentary they generate? Also, most of the commentary is informed and well-thought-out. It speaks very well of The Kneeslider and its readers.

  53. Sportster Mike says

    November 16, 2010 at 5:47 am

    Nice bike (rocket) and good posts and sensible discussion
    Now I know why I like Kneeslider so much
    Looks like we have a new Bert Munro
    be interesting to see how he does…

  54. Bob Nedoma says

    November 18, 2010 at 6:16 pm

    No tailgating behind this one.!

  55. Paulinator says

    November 19, 2010 at 7:54 pm

    Todd, the calculator says I should get about 65 mph out of a 12 horsepower Morgan. Not bad!!! My little GY6 engine can make that power for at least 3 minutes before I hear that familiar “ice-cubes in a blender” sound….again.

  56. GenWaylaid says

    November 24, 2010 at 6:00 am

    Did anyone else catch that the bike only weighs 160 pounds? There’s not a single part on this thing that doesn’t do double duty looking good and going fast. Throttle? We don’t need no stinkin’ throttle! Just a button for 100%. What an incredible piece of engineering.

    Would I ride it? Of course not, but…after seeing that night shot I really want to take it out to a Nevada ghost town and shoot a B movie. An entire gang of zombie vampire biker thugs against one violent, unemotive hero on THIS.
    First thug: “If that sum’bich comes back here I’ll…”
    Second thug: “You hear that?”
    BwaaaaaaaaBWAAAAAAAbwaaaaaaaaBWAAAAAAAROOOOOOOAAAAARRRRR!

    Bring lots of fuel and fake blood, kiddies, it’s gonna be one heck of a ride!

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