What do you think of this frame for an MB?

Discussion in 'Photos & Bicycle Builds' started by lowracer, Nov 5, 2010.

  1. lowracer

    lowracer Member

    I am thinking about getting this frameset for my next MB project. It is a Dirt Jumping frame for MTB size wheels (26" aka 559) & looks very heavy duty @ around 6 lbs.
    Opinions welcome
     

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  2. ocscully

    ocscully Member

    There does not appear to be any room to mount a motor in the frame shown?

    ocscully
     
  3. RedBaronX

    RedBaronX Member

    right-- that is a crazy beefy looking frame, but there is not enough space for a in-frame mounted motor. Put a rack mount on that and you would be unstoppable though.
     
  4. lowracer

    lowracer Member

    Oh yeah, Sorry I forgot to mention that it will be a front drive belt drive (kinda like my current MB) but with a bigger engine. Here are some pics of the items going on it & a pic of a fellow MB'er bike that I drew inspiration from.

    I just put together the front wheel, Whizzer sheave & Marzocchi Bomber fork from stuff I had laying around the garage. This wheel is actually a single speed rear wheel (no dish), that I removed the quick release axle & installed a solid axle. The extra length will be perfect to attach the vertical steel mounting hardware for the front engine rack that will be fabricated w/ 3/4" steel square section to hold the Lifan 2.5 hp 4 stroke.

    -lowracer-
     

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    Last edited: Nov 5, 2010
  5. lowracer

    lowracer Member

    Ok,
    I got the new engine ordered on eBay for $90
    I got the new bicycle frame ordered on eBay for $90
    I got a nice used Comet pulley clutch ordered for $40
    Hardware from Lowes & my local Ace Hardware for $30
    The rest of the bike parts I already had to complete the build.
    Will post pics as parts start arriving.
    This is getting a bit too addicting...lol
    -lowracer-
     
    Last edited: Nov 9, 2010
  6. lowracer

    lowracer Member

    Got most of my parts delivered & have been working on the engine mount. Here are a few new pics of the build in progress.
    -lowracer-
     

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  7. wheelbender6

    wheelbender6 Well-Known Member

    That RM frame looks indestructible. Why do you prefer the front mount?
    So it doesn't interfere with your ability to pedal?
     
  8. lowracer

    lowracer Member

    wheelbender6,
    I installed my Subaru Robin engine on a rear rack once before to see how I'd like rear drive & as a test bed for comparison reasons. It stayed on for a few days of riding & I came to the conclusion that I like front drive far more. The weight distribution & handling is better with the weight of the engine on the front wheel driving the steering thru turns. I also like the fact that the rear pedal drive is totally independent of the motored drivetrain. The cable run to the throttle is very short & if I need to reach forward to choke the engine its easy to do while moving. The biggest reason I prefer front drive is the stealth. When cars are behind me, they dont see a motored bike, just a bike going fast with no pedals turning. They see a bike like any other since the motor is on the front. I also like to see & hear what the engine is doing. I had alot of heat on my butt having the engine mounted on the rear directly above the wheel, & while standing on the pedals to pedal, the weight was all wrong.
    -lowracer-
     
    Last edited: Nov 16, 2010
  9. lowracer

    lowracer Member

    Received the Syncros DH headset yesterday & installed it.
    Very nice unit with steel cups & cartridge bearings.
    Here are 2 pics.
    Will be changing the handlebars out in favor of upside down MTB riser bars.
    -lowracer-
     

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  10. lowracer

    lowracer Member

    I installed the front brake & got the motor mount just about finished today.
    I'm using 2 old school 1/2" skateboard truck riser pads made out of heavy rubber.
    The 4 engine bolts will go thru these riser pads & it will absord alot of vibration. I ran this Lifan 152F (97cc) engine on the concrete to see how she sounded & it purrs like a kitten. Here is a pic of the pads.
    -lowracer-
     

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  11. lowracer

    lowracer Member

    Got the engine mounted today.
    Here are some new pics of how its coming along.
    -lowracer-
     

    Attached Files:

  12. iRide Customs

    iRide Customs Member

    Wow...that looks like a lot of weight on the front. Why didn't you try to mount it on the back of the bike?
     
  13. lowracer

    lowracer Member

    iRide,
    I prefer the engine on the front & like the way it handles up front & front wheel drive. Its not that heavy but looks big & bulky. If I took the tank off the top & put it elsewhere it would look better & be only slightly larger than my other MB with the Subaru-Robin up front.
    -lowracer-
     
  14. Wheres my dog

    Wheres my dog Banned

    Safety has always been first for me in every venture I set out on....

    That is an awful lot of weight forward of even the center line of the front axle itself... please do a good amount of low speed testing before unleashing the power of the engine!

    I might even encourage you to purposely hit some potholes or grooves at low speed to see how it handles!
     
  15. lowracer

    lowracer Member

    Wheres my dog,
    I've been riding it around unmotored for the past week since the engine was installed. This frame has a rearward weight bias similar to my Rocky Mountain downhill bike & it feels good just riding around under pedal power with the motor up over the front wheel.
    It doesnt weigh much more than my Subaru-Robin w/BMP kit although it looks huge.
    Don't forget the heaviest part of the MB is me sitting on it (165lbs)...
    -lowracer-
     
  16. lowracer

    lowracer Member

    She's Alive

    Got it mostly done now except still waiting for a Steel Flex Pipe to replace the Silicone tube, some Clamps & Permatex Copper Gasket goo are on the way too. Here are a few pics of the almost finished project. Using Kryptonics 'Kryptos' skateboard wheels to tension & route the v-belt within the engine mount. She hit 53 mph the other day and was fairly stable...lol
    -lowracer-
     

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    Last edited: Dec 17, 2010
  17. ibdennyak

    ibdennyak Guest

    Wow, 53. Your ratio must be about 6-1 I assume? Is your governor disconnected? That's impressive.....mine topped at about 38 with a 9-1. Course it was a lot heavier too.
     
  18. lowracer

    lowracer Member

    ibdennyak,
    I haven't removed the governor, but I attached one of my daughters rubber band type hair ties to the governor arm & to the engine block to pull the arm when it wants to close the throttle at higher rpm. I really dont have the need to wind this engine up at this gear ratio since I dont ride much @ 50 mph. 40'ish is good enough for me.
    The engine pulley is 3.2"
    The wheel pulley is 15"
    The wheel is 26.5"
    Engine max torque @ 3000 rpm's = 50 mph but the engine is rated for 3600 rpm's.
    I used a gear ratio calculator building this MB but alot depends on the engines ability to pull the load thru the wind. This Lifan 2.5 is a strong, quiet little bugger.
    -lowracer-
     
    Last edited: Dec 19, 2010
  19. 4950cycle

    4950cycle Member

    Long time

    Low, just checkin out when and the details of your combo and build. I didn't know you did the math on your ratios .
     
  20. lowracer

    lowracer Member

    I think I found my gear ratio calculator at the Max Torque clutch website, Here is the link. Just need a tape measure to measure your pulley diameter, sheave diameter, & tire diameter.
    http://www.maxtorque.com/html/speed.xls
    -lowracer-
     
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