DIY Friction Drive Experiment

lowracer · Oct 10, 2011

I've been wanting to make a super-simple friction drive for some time now & think I may be onto something here that could work well on both a hardtail or a full suspension by allowing the engine mount to swing. It is attached to the set tube. Its basically a front wheel hub mounted in a 31.8 steerer stem attached to the seatpost with a 27.2 to 28.6 shim. Take a look at the pics....I'll probably run another arm off the non-drive side for balance & added strength. The clutch driver is a 1/2" Staton unit I also use for v-Belt pulleys. I may use bungee cords & mount a brake lever & cable to lift the unit for coasting or pedaling without friction.
-Lowracer-

NormO · Oct 10, 2011

Very nice idea. I like it a lot. Hope it works out.

lowracer · Oct 10, 2011

NormO,
Thanks bro.
I've been thinking about it some more after posting these pics & will definitely add the opposite side arm & connect the 2 with some cross bracing & 2 alloy legs instead of the bungee/cable idea. I'm probably putting the Stage 7 pocket bike engine on it & it will need to be as sturdy as possible to handle the power.
-Lowracer-

wayne z · Oct 10, 2011

Awesome! I luv your innovative use of standard parts to achieve this floating drive train that can be used on suspension bikes, Kudos!!

lowracer · Oct 11, 2011

I was excited today to receive my new Stage 7 Pocket Bike engine rebuild kit today via DHL from China (took only 2 days & free shipping). I bought this to repair my blown pocket bike piston & cylinder (running a way-too-lean Jet experimenting with jetting (won't do that again!)
So I put that engine back together, then bolted it up to the unfinished new DIY friction drivetrain. I had to use a vice-grip to lock down the arm tight against the tire for the test-run. I was impressed with the drivetrain & newly rebuilt engine. I didnt go far or fast but got a good feel for the new setup & really like it so far. I did order a new AX-81 V belt yesterday just in case I want to switch out the friction drive in favor of a rear v-belt drive (with a few major modifications...)
-Lowracer-

happycheapskate · Oct 11, 2011

I was wondering what was going to hold the roller down. Looks like it would work best with 2 arms, even if you just use one tie-down strap/bar. The muffler sure is close to the ground though!

lowracer · Oct 12, 2011

HappyCS,
I am going to be adding that 2nd arm to the other side soon. I just wanted to get it done enough for a few test drives w/ the newly rebuilt engine.
Actually the sausage muffler on the bottom fell apart yesterday, so I took it off & threw it away. Unless I buy a different expansion chamber or bend some conduit or get a flat pancake style muffler, I'm gonna live with the low rider exhaust.
-Lowracer-

lowracer · Oct 13, 2011

I added the 2nd arm & tried it out using an inner tube as a bungee cord to pull the assembly down into the tire for friction.
It isnt a good way to do it (wants to jump around under power).
So, I'll be going back to using a one-sided aluminum upright for support & ordered a seatpost quick release on eBay for $6.00 to be able to adjust tension.
I'm probably going to get a DAX canister type muffler for this rear friction drive experiment to eliminate the hanging expansion chamber & quiet this thing down alot.
Yeah it will hurt the top end power, but on this no suspension bike, I'm not worried about top end power.
-Lowracer-

cannonball2 · Oct 13, 2011

Hey LR, my experience with the PB engine on an FD showed the down force to positively drive was pretty high. The PB has so much power, that is is easy to break it loose if you dont accelerate slowly. If the HP #s they claim are close it should turn a larger roller, maybe 1.5/1.75" especially where you live in the flats. If you could turn a 1.75 to the 11K PB rpm it would be 57mph-WOW!

lowracer · Oct 13, 2011

CB2,
On this bike, I gotta keep the roller small & keep the speed down. I dont feel safe traveling fast on a no suspension lightweight bike. Now on 'The Beast' I feel totally safe going 50+ mph & may adapt this friction setup to go onto the back wheel of 'The Beast' & do like 5-7 Heaven & have a dual engine bike.
-Lowracer-

lowracer · Oct 13, 2011

CB2,
I removed the expansion chamber today & just for kicks, I installed a large lawnmower muffler. It was un-godly loud & obnoxious, so I removed it & am eagerly awaiting the nice little canister muffler that should tone down this badboy. I also installed the dual single-sided support struts (1/2" thick aluminum) today to lock the arm holding the friction roller down against the tire. The seatpost quick release I ordered should arrive in a day or two & then I can replace the nut & bolt now holding the locked position with an easier-to-adjust quick release. I also received the AX81 v-belt today & will hang onto it for the one day I want to switch this back to a v-belt drive.
-Lowracer-

lowracer · Oct 13, 2011

Here are a couple of pics taken today after the modifications done in my previous posting.
-Lowracer-

happycheapskate · Oct 13, 2011

Was it a standard Briggs 5hp type muffler? I have been wanting to know if pocketbike mufflers worked on HT's and other bike motors. If this muffler fits on your pocketbike, they should be interchangeable with the proper bolts/studs.

muffler

lowracer · Oct 13, 2011

HCS,
Yes, but different than the one in your picture. Its a Sausage type w/1" threads bought at ACE Hardware for $3.00. I had used it on my Lifan 2.5 engine with success, but these pocket bike engines are louder.
-lowracer-

lowracer · Oct 15, 2011

I received a DAX canister muffler today & had to do some testing. This muffler is made for the GT50R engine (same engine I got from ZeroPulseUSA on eBay).
I wanted to quiet this engine down a bunch & didnt feel like buying another REV expansion chamber like I got on 'The Beast' for $40. So Cannonball2 was nice enough to sell me his DAX muffler & I quickly got to experimenting. Before it arrived, I did some tweaking to the expansion chamber I already had that was too loud in stock form. I ended up cutting off the stinger & silencer & installing a large ACE hardware sausage muffler as the silencer. Then I did away with the 12" flex pipe header (leaked after time) & hooked the chamber directly to the exhaust spigot. Performance suffers without the 12" lead header but for this no suspension bike, I'm not too worried about top speed (scary fast either way). Here are some pics I took today of the bike both ways.
BTW, this expansion chamber is now quieter than the DAX exhaust canister muffler & the REV expansion chamber with 12" flex pipe header on 'The Beast'. It has more power bottom & top than the DAX canister, but less power than pipe setup on 'The Beast'.
-Lowracer-

5-7HEAVEN · Oct 16, 2011

Great job, lowracer. I admire your skills!

lowracer · Oct 16, 2011

5-7,
Thanks bro...
I got another pocket bike engine coming in the mail that needs a new top end. I think I will repair it & if so, possibly use this friction drive experiment to add a 2nd engine to the rear wheel of 'The Beast'. I liked what you did on 'Dragon Lady' & got the idea from you Sir.
Overkill might be the correct word to use adding a 2nd engine onto 'The Beast'. It already accelerates real well, can hit over 50 mph, & cruises @ 30mph effortlessly. Trick here is having a pivoting mount Friction drive solidly mounted to the bottom of the seatpost & as the suspension moves, so does the friction drive arm...
So I am not dead set on keeping it on there if I do put it on there, but in the quest for knowlege & the need for speed, I wanna see what happens...lol
(Spoken like a true mad scientist).
-Lowracer-

5-7HEAVEN · Oct 16, 2011

You will experience an increased rate of acceleration and torque at all rpm levels. Both engines will be shouldering the load; you will "feel" their relief. Torque is also what you'll feel, not hp.

And then there's the idle of two engines.

However, the sweetest sound you will hear is the "drone" from low through midrange.

It's indescribable. dance1

lowracer · Oct 16, 2011

5-7,
Its sounds ever so tempting...
My only question has to do with the Police?
Does adding (2) 50cc engines to a bicycle blow the 'gray areas' of the law away?
I spoke to a local police officer here in SC & he said my bike was totally legal since it is under 50cc, under 2HP & goes less than 30mph (lied a bit on hp & speed).
He also said as long as I'm obeying the rules of the road & am not clocked going 50 mph, I shouldn't get pulled over.
Will hauling 100cc of screaming pocket bike engines void my legality?
-Lowracer-

lowracer · Oct 16, 2011

Ok,
I have formed a profound opinion today about friction drive on high powered engines (5-7 wasn't kidding).
I put the expansion chamber exhaust back on, due to it actually being quieter than the DAX canister muffler with more performance. I rode it around a bit after getting the roller pressure dialed in after a few test drives. I took it for a few mile run to make sure all was good. I even took these last two pictures of it in the sunshine to keep fond memories of the pocket bike engine friction drive experiment.
But, I then proceeded to dis-assemble the drivetrain since I now can honestly say, I don't like friction drive. The new tire is already showing signs of wear & there is tire powder all over the rack. I filed down the points on the new roller prior to any test drives as experience has taught me & never had the roller loosely against the tire to allow roller spin (superwear)...
I guess friction drive is ok for weaker engines like my Subaru Robin EH035 (little tire wear on my BMP setup) but this pocket bike monster will chew a tire up & spit it out.
I already started planning the rear rack mount for running this bike using another of my 'Lowracer V-Belt Drives'.
V-Belt drive has alot less friction than Friction drive w/ higher top speeds & more fuel economy.
I'll start a new thread to catalog the new buildup once I get started.
-Lowracer-

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