DIY Friction Drive : Lowracer Style

lowracer

lowracer

New Member
Since dismantling the pusher trailer I recently built, This new project started out as a center engine mount using the jackshaft & pulleys to power the friction drive roller. I didnt like the jackshaft & felt like it ate up too much power w/ additional friction, so I simply mounted a BMP roller onto a Staton 1/2" double bearing clutch driver unit. There is definitely much less friction running it directly without the added complexity of the pulleys, pillow blocks, jackshaft & mounting hardware, & so far tire wear seems low (no black dust all over the place). I think the Maxxis Hookworm 2.5 is a good tire for friction drives since its so HUGE. The whole mount took me half a day to build & has a nice quick release to the inside for the up & down roller adjustment. I'll leave it like this for a bit. Maybe beef it up with additional supports, maybe install the expansion chamber & a single speed conversion for the cassette & probably a 32T front chainring instead of the 46 on there now...
-Lowracer-
 

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wheelbender6,
Thanks...
There is a black quick release inside the main support rail (near the air filter) that allows up & down adjustments of the roller. You can see it in the close-up pic.
-Lowracer-
 
MaxPower,
I had to try the jackshaft since I wanted to get the engine perfectly centered (unlike all the friction drive kits). Unfortunately, the jackshaft & all its added complexity hinders performance. There was a very noticeable difference just pedaling around with the roller engaged comparing jackshaft to direct. I played with the jackshaft a bit re-adjusting everything & lowering belt tension but still...
I'm also from the school of 'Keeping it Simple' so removal of the jackshaft & going back to direct was a no-brainer.
We'll see how tire wear goes, but for now I'll leave it as a friction driver. If tire wear becomes an issue, I'll rebuild the rack to run the engine the other way & go v-belt drive.
-Lowracer-
 
Put some hefty down tension on it. When I had the PB engine on the FD set up it would spin the roller like crazy if you werent care with throttle on take off, just has so much power!. Once going it seems to wind up forever. Watch it for over rev, as I would imagine it will rev higher on the FD than the belt drive. Should be a cool ride!
 
CB2,
I rode it around a bit & played with roller tension. It didnt slip using light pressure & I was very surprised. I think these Maxxis Hookworms are awesome tires for this type of application & may have alot to do with this test.
MaxPower,
I think it was just friction or stiction & really suctioned...lol
-Lowracer-
 
CB2,
Its raining here today, very cold lately & I'm getting sick. I'll try to put a few miles on it over the weekend if things warm up to post more comments, but so far so good...I am liking this friction driver!
Keeping it simple works for me...
-Lowracer-
 
Yeah the weather hasnt been great for riding lately. Glad your first impressions are positive. What size roller is it running? Hope you feel better!
 
CB2,
Its a 1.25" BMP roller that I file the points off of.
The sharp points eat tires & filing them was a trick I learned from Jim @ BMP.
Should get around 40 mph which is plenty for the hardtail bike...
-Lowracer-
 
Re: DIY Friction Drive : Lowracer Style...switched to V-Belt Drive***

Well,
I'm back to my old ways again, not wanting to leave well enough alone.
I like friction drive, in fact I took one of my MB's to work yesterday (around 60 miles of riding). This is the one with the Subaru Robin EH035 driving a BMP friction kit. The thing performed flawlessly & got around 135-145 mpg's. Just needs more power to drive thru the wind and to cruise at over 30 mph without being at WOT the whole time.
I didnt much like the DIY friction set-up on this bike with this engine, so I went & converted it to my tried & true v-belt drive. It gets out of its own way in a hurry now & easily cruises at 30 mph at half throttle.
Here are a few pics...enjoy
I'll probably install the expansion chamber after I do some more test drives.
-Lowracer-
 

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Isnt this sorta where it all started? Dont guess youve tried an inframe? I think you must be kinda like me, if there is an extra engine laying around, its gonna go on something some how. I think Im finally out!
 
CB2,
I cant tell you how many times I've mounted & remounted every variation of engine & drive-type to the three MB's I have now.
I am more fond of front wheel v-belt drive, but on this bike, I like the rear drive.
I have never considered in-frame & probably will stick to just either front or rear drive.
I still have 2 engines laying around (yours & a new Tanaka PF33) I'll probably keep the extra Pocketbike Cag for spares & who knows what the Tanaka will end up on???
-Lowracer-
 
I took the bike in its current configuration (v-belt, rear drive, rear mount) for a ride today to make sure its set up correctly & made a few adjustments. This is a sweet set-up & has great acceleration right off the line & pulls strong to an impressive top end.
Hopefully I wont get a wild hair & will leave it like this now for awhile.
I tried to mount the expansion chamber today but wont be able to without modifying it with some flex pipe to clear the frame. I'll stick with the little exhaust can until I get motivated to change it. Performance suffers a little with the small can, but isn't as bad as you would imagine.
I'm still in love with these little high performance Cag engines & although I started busting clutch springs I can't imagine going back to just 1.6hp full time...
I may give this new MB a workout this week by taking it to work one day & putting about 60 miles or so on it. I gotta come up with a name for it too I guess...?
-Lowracer-
 
Did some more measurements today & confirmed a 16:1 drive ratio.
This should easily get me to the upper 40 mph range at less than WOT (10k RPM's).
My other Cag-stage 2 pulls 11K rpm under load & breaks 50 mph on 'The Beast'.
7000 rpm's = 32 mph & just when the engine is getting into the powerband...
Gotta put some miles on this new rig to see how she holds up.
-Lowracer-
 
Today just for the heck of it, I swapped engines & installed that new Tanaka 33cc engine I got on Amazon a few months ago. It bolted right up but I had to solder a new cable to fit the Tanaka throttle assembly. It started up on the 3rd pull & since starts on the very 1st pull. I took it out for a few test drives & made a few observations.
1) I can't go back to 1.6 hp (anemic) & need to sell the Tanaka (anyone interested?)
2) Although the pocket bike engine has its fair share of maintenance issues (breaking clutch springs, spitting fuel, loud as heck) its such a powerful little powerplant & my favorite so far.
3) I'm addicted to MB'ing...lol
I did have a bit of fun today with a scooter that I never saw in my rearview mirror.
He passed me & at the time I must have been traveling around 30 mph.
I pulled some throttle to catch up & since it was windy, I tucked in for some aero benefit.
I caught him after a few seconds & I think I surprised him. We rode side by side for a few miles like CHIPS police motorcycles.
I ended up turning right at the next light to go over the Ravenell bridge into downtown Charleston & he was making a left towards Fort Moultrie, so we waved our goodbyes.
I did an additional 60 miles using the MB to do my work again today & 30 of them with another broken clutch spring (arghhh). I'm starting to use the MB more & more for business/commuting & am loving the fuel economy. I do need to figure out a better way to bring more fuel with me to extend my trips into the 100+ mile days. Right now I am just using the 1 liter fuel tank on the engine & another 20 oz of fuel in an MSR bottle in the bicycle water bottle holder (velcro strapped in to prevent a fuel grenade launching)
I gotta get the breaking clutch spring problem under control & may just change clutch packs to see if a different design works out better?
-Lowracer-
 
Hey LR, am toying around with mounting a 1gal plastic fuel tank from a Tecumseh 10 hp engine on the the handlebar stem on one of my Lifan FDs. It will be high enough to flow the fuel and its much narrower than the bars so it looks ok. I dont think the weight will be an issue as I routinely carry a gallon in a can on a rack over the front wheel now when on extended runs. Will allow me to remove the small tank over the engine for a lower leg over height. Got the mounting worked out. Will post pics if I do it.
 
CB2,
Show me some mock up pics is u can so I can see what it looks like.
I gotta get more fuel on the bike but since I still pedal I dont want a top tube tank that would interfere with my legs. I also dont want the bicycle to resemble a motorcycle...
-lowracer-
 
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