Am I sane?

Discussion in 'Friction Drive' started by prism, Sep 3, 2007.

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  1. prism

    prism Guest

    I currently have a suitable bicycle, as well as a) machine-tools; b) experience with engines, motorcycles, and related things; and c) some real questions, some of which might sound weird.

    1) I am currently thinking of going rack-mount friction drive using a four-stroke motor. I've heard how these setups tend to devour tires and slip in inclement weather, and I just might have a partial solution. It involves two rollers pivoting such that both rollers contact the tire at 'ninety degrees', with the rollers being roughly 1.6 inches outside diameter and coated with grit of some kind. (aluminum oxide, silicon carbide, others.) The central shaft drives both rollers using #25 chain, and in turn is driven from the engine clutch using the same type of chain. (I'm working on the drawings still)

    Question: do I need to have my head examined?

    2) While I do not mind the smoke, smell, and noise of two-stroke motors, I strongly suspect discretion is advisable in my case - hence the use of a four-stroke. I'm leaning toward the Honda GX35, though I've read about the Subaru Robin eoh35.

    Question1: is the Subaru Robin a 'better' (term used loosely) engine?

    Question 2: I've heard my share of weed-cutters, backpack blowers, Go-Peds, motorized skateboards (long years ago) and related engines. I've not yet heard either of the two engines mentioned previously. Are they significantly quieter, or is the chief difference the tonal quality of the engine noise compared to say, uh, a Zenoah or Tanaka? I'm prepared to assemble a large-volume muffler if needed - and should I do so, I can just hear the comments:

    "What is that thing there?" (points to muffler)
    "The muffler. Why?"
    "I've never seen an engine that small with a muffler that big..."

    3) My goal is to manage groceries and related shopping on a semi-regular basis, and longer trips (possibly hundreds of miles) now and then. Currently, I need to lose a great deal of weight (enough that I'm embarrassed to say how much), I've had surgery on both knees (they complain if I ride any real distance), and I wish to avoid undesireable attention (chiefly from constables). Also, I will commonly be towing a trailer (one of which I already have; I hope to make another.)

    Question: I'm planning on gearing the thing such that normal 'cruising' speed is in the ten to twelve miles an hour range. (i.e. 5,000 rpm or so; both engines have their torque peaks in that region.) I've seen signs locally describing distances and 'nominal' times for bicycles, and that speed range seems to fit. (It's also nearly double what I can pedal for any distance).

    Am I crazy? I know these setups are capable of higher speeds, but I do not feel comfortable traveling at twenty-plus on a bicycle. (Besides, I'm not a teenager any more - top of ten gears, a slight downgrade, chain singing, and clocked at 50+)

    Thanks in advance for your consideration

  2. ironwarlock

    ironwarlock Guest

    If you just want to putt and you keep your gear ratio that low you will have great power. Great hill climber. I don't know if I would go with the friction drive. I would say the friction drive would be the worst performance.(tire wear,wet slippage and to much unnecessary presser on the rear tire for starts). Chain or belt would be better.
  3. OldPete

    OldPete Guest

    We are on the internet need to hold back.

    If you are 300#++ and going to pull a trailer full of shopping, go for the Staton set-up. David Staton only charges $55 for a 48 x 12g stainless spoked rear wheel, as long as it is bought with the kit. Mr. Staton likes the R/S 35 over the 35cc Honda, he has a short article as to why over at his site but I could not find it. The Tanaka 33 is a bit more powerful and quieter that the Robin 35 but does requior mixed gas. When using the R/S35, the Staton set-up does not have the fuel tank issues at fill-up that the GEBE system does with some bicycles.
    David will help you select gearing for 20mph and that can always be changed at a later date anywho.

    Portland = damp & rain so a friction drive is probably not a good idea.
  4. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:the 35cc ROBIN engine is very tame, and has more than enough power for your needs. in fact, ya might get by with the smaller 25cc ROBIN.
    i had the 35cc friction drive. a pedestrian standing right next to me stated that my engine was very quiet at idle. that's without a muffler.
    unsure if friction drive will work for your environment. gear chain drive might be overkill under 20mph and low HP. GEBE setup and 25cc ROBIN would probably work best for you.
  5. StreetPlanes

    StreetPlanes Guest

    Robin-Subaru VS Honda

    I own a Robin-Subaru and Honda powered bicycles. (I should say my partner and I own them.) Here's what we know:

    In terms of MPG and power-- no difference that we notice. No, we've never drag raced the two of them nor have we put them through time trials. We've ridden then daily and switched from time to time and can't tell much difference. My partner weights about 150 lbs and I weigh 208 so a drag race wouldn't prove much anyway.

    In terms of money-- same cost for both engines.

    But here's where things differ: The Robin-Subaru is built in Japan and has a steel cylinder liner. The Honda is built in Indonesia and has aluminum cylinders with no liners. My guess is both engines will remain about the same until time for a rebuild. The Robin-Subaru you rebuild, the Honda you throw in the recycling can or scrap metal pile.

    As for comparisons to 2 cycle engines I can be of no help. The only 2 cycle engine I own is a 45 year old Homelite Chain Saw that belonged to my grandpa, my daddy and now me. Motor runs great but the chain and bar are shot again. (You would not believe how many chains a saw can wear out in 45 years.)

    In the good news department: I mated a Honda to a CVT transmission today in the machine shop. Now we've got to build a frame and see if we can break it.

    You mentioned the friction drive and the dual rollers. I'm not saying my idea is better but give this some thought: They make tires that are slicks in the center and knobby on the sides. (Sort of an on-road-off-road tire.) What if a roller was designed so that it had gear teeth on both ends that would engage the knobby portion of the tire? Mass production would probably require castings but one-offs could be machined.

    Also, on friction drives: I like the idea of grit covered rollers but what if you used one hour glass shaped roller that sort of wrapped the tire instead of two rollers? Just a thought.
  6. StreetPlanes

    StreetPlanes Guest

    I think if you use a decible meter the 4 strokes and 2 strokes will register about the same but the tone of the 4 stroke is a lot easier on grumpy old men like me. Those "bees in the can" make my head hurt.
  7. dbigkahunna

    dbigkahunna Guest

    Dimension Edge

    I have a DE set up with the wooden rollers and the carborundum wheel. While the area I live in is, uh not wet I don't know if I can give you great advice. However I have been surprised how well the wood rollers grip the tire. I am going to upgrade to a Maxxis Hookworm tire on the rear. This should give plenty of grip to the roller. Just looking at the roller, if you chucked it up in and took some sandpaper to it to make the roller fit the tire where it is gripping it on part of the sides as well as the top of the tire, there should better grip. The wooden roller does not seem to wear the tire like the rock does. And DE claims they have a roller that will work in wet conditions. DE has been in business a long time and while I bought my kit off ebay, it is of great quality and except for two plastic do-hickeys that have been removed, the thing works well.
  8. smapadatha

    smapadatha Guest

    Comments from a GEBE newbie

    I did a lot of research before I went with the GEBE/kit. It's not perfect, but I'm still convinced I made the right decision. If you went with the GEBE/kit and got their Velocity rim with the 12g spokes, I'd be very suprised if you broke any spokes, especially if you tied the spokes and kept the wheel trued.

    I have the R/S 35 cc and recommend it. The only disadvantages I know of for this motor is that the R/S engineers assumed you would have no problem tipping the motor nearly 90 degrees to fill the gas tank or to empty the motor oil. It just didn't occur to them that it would be bolted to something awkward, like a bicycle.

    I suspect that both of these inconveniences can be overcome by:

    1. Using a Liquavac. ( I bought one for $30 at Lowes. It is a hand pump vacuum designed for vacuuming oil out of small engines.

    2. Installing an auxilliary fuel tank. This not only solves the problem of having to tilt your bike at an absurd angle to fill the R/S "u" shaped gas tank, but also extends the range of your bike.

    Please note that I am currently still field testing both of the above items, so I'm not able to recommend them yet.

    About the engine power and gearing issue, keep in mind that, just because you have a bike that can go 30mph, doesn't mean you have to! I rarely go that fast, but it's very nice to know you have that power in reserve when:
    - You are on a street with no bike lane and you want to ride in a car lane to avoid the "door zone".
    - You need some reserve power to scoot out of someone's way, or when you are crossing a freeway access ramp.
    - You are going up a *very* steep hill or towing a heavy trailer.

    Also keep in mind that, the more you ride, the more skilled and comfortable you will be riding at higher speeds. There are plenty of bicyclists who will occassionally reach 30 mph, without a motor.

  9. larymor

    larymor Guest

    GEBE R/S35 owner

    I have the R/S35 GEBE belt drive setup and would highly recommend it. I haven't had ony other engine or drive system so I can't comment on that. The only problems I have had are the same ones Sam mentioned in previous post...gas tank...oil change. Also the mounting of the engine....which is discussed in my setting up R/S35 thread and a lot of others, which you should take the time to read if you haven't already. I do not travel over 10-20 mile roundtrips, so I get by carrying a MSR fuel bottle...$12-15 at sporting goods store.. (33OZ) in my sidebag to get me to a gas station if I run out. I love puling up to the pump and putting in 25 cents worth of gas while the guy next to me is putting in $40.00 worth!! Also no mixing oil with the just 'filler up!! I solved the oil change problem by using a old anti-freeze tester I had laying around to suck the old oil out...and a old turkey baster I had which I had used to suck old power steering fluid out of my vehicle ( that stuff goes bad too ) to refill the R/S35. The engine is very quiet at idle..which I set very low, but at acceleration gets fairly loud but is not as irritating as a two stroke weed whacker engine sounds. I am also thinking of getting a small trailer for store trips where I cant get everything in my bag. Welcome aboard Prism!
  10. prism

    prism Guest

    The original post might have been "too long", so I did not include the following:
    1) I had planned on making the 'rack' such that removal (with the proper tools) would be a five-minute affair.
    2) I had hoped to eventually fit disk brakes.
    3) I really want to lose weight, but have had no luck as of yet. (Yes, I do walk as much as I can, and I try to be careful as to what and how much I eat.)
  11. dbigkahunna

    dbigkahunna Guest

    Loosing Weight

    I thin what you will find is where you MAY have ridden the bike 2 a week, when you add and assist, you ride it every day. And where you rode 3 miles you now ride 10. I have ridden my bike more the last month than the last 5 years.
  12. bamabikeguy

    bamabikeguy Active Member

    I'm really warming to frame-mounting, but really see no reason to remove the mount, and with frame instead of axle mounting, tire repair is a lot easier.

    It's best to go into this with a good sturdy frame, and the idea that IF you ever get tired of it, you could sell it as a motorized unit to somebody else.

    And I'm gonna be bragging about the Greygeezer Bike I just finished, for older and heavier riders. Only thing I can't change is I'm spoiled by the 12" saddle, can't get comfortable on narrower models.

    I have a guy, Jack, whose dropped from 275 to 240 in a little over 8 months, and the ONLY thing he does is half throttle, with the 11 tooth trail gear, peddle along at 15 mph.

    He does it daily (belts run in rain), to the cafe about 10 miles away, for lunch.

    He's addicted to the daily rides, so does probably 200 plus miles per week.
  13. Hive

    Hive Guest

    Engine - Drive Choices

    Well, it appears you are taking your time making your choice.

    I must also assume you have read the Rack 'em Up "Sticky" "How Does GEBE System..." post, and the Dooz and Do Not Dooz, etc post and the GEBE Recumbent stuff under Discussion or Pictures - whatever.

    There is a lot of good info on the GEBE system, if you search it out patiently.

    Briefly, the 25 Honda I had was fine, but the 2-cycle T-3300 is better. The Honda worked well on the flats, but not so good on hills. Needed to be broken in longer, but its smaller clutch limits its potential if torque is needed. Other than that, it is a good choice.

    The T-3300, with its large clutch is better choice, for me anyway, though I detest oil mix and low mileage break-in. Regardless, that little motor has better weight-to-HP ratio, and when it finally gets "broke," it should run great.

    The Tanaka is louder, but not not offensive. On my bent, the exhaust is about a foot below and back of my right ear.

    All of these trimmer motors have built in mufflers behind the protective covers, be they 2-cycle or 4-cycle and are quiet enough.

    If you think about it, and wish to pedal as well, the belt drive GEBE offers some favorable options:

    Free ride, which is a very big thing to me, by removing belt (which you can do without removing drive gear cover.)

    The choice to motor and pedal along is available for fitness. Pedal out, motor back, etc.

    GEBE engine is installed without drilling frame etc., so removal and transfer leaves former frame without holes etc.

    Normal tires and no slippage if wet, and some dirt-hill runners swear by them.

    Lastly, these trimmer engines are well made, tough and less troublesome; and, though seemly bomb proof, if something does happen, the engine can be removed and the bike used with minimal inconvenience, etc. Lots of shops fix these motors and are familiar with them, if warranty is over, etc.

    Good luck.
  14. prism

    prism Guest

    I had a chance to see both the gx31 and gx35 recently, and while the -31 has four tapped places on the bottom of the crankcase, the -35 does not (perhaps it has two, if that.) After examining the available data (downloaded 'shop manuals') I came to the conclusion that I'm going to need to mount off of the clutch. Given that, the Robin seems the best of the three (and no, it does not have a cast iron sleeve for the piston, according to the shop manual. It does, however, have a needle bearing for the wrist pin.)
  15. Hive

    Hive Guest

    A Suggestion on the Engine Choice

    If I understand your reply correctly, and, assuming you are going with the GEBE system, the two-bolt mount employed by them has the bracket attached to their clutch/drive housing and I believe the measurement for belt centering is somewhat critical. The engine will come attached to the housing from GEBE.

    Frankly, if you are going with the 4-cycle motor, I would stick with their Subaru/Robin engine, even if it costs a bit more from them than if you buy another engine separately. I suggest this from experience. The engines they (GEBE) supply are every bit as good as the Honda or better. If fact, the differences are not worth the trouble.

    It will save you time and grief, honestly.

    Consider the weight factor as well. The lighter T-3300 will deliver same HP as the either the Honda or the R/S 35 but with the weight of a 25, but I believe its torque is much higher. It also sits much lower.

    I cannot comment on the noise, save the GX25 was very quiet, so I must assume the 35 is not much louder.

    I might add that the Tanaka is popular for a good reason.

    The Tanakas are chrome lined and I think the S/R are as well, but regardless, they run forever, relative to rider use etc.

    And, think about installing a Sinz or similar brake lever for a throttle - way better than the ones sent with GEBE kit, even if you have to buy a different cable, which is unlikely, unless you have a longer frame. If you want one that can be set at one speed as you go, let me know. I have one I bought and never used.
    Last edited by a moderator: Sep 12, 2007
  16. prism

    prism Guest

    more confusion

    firstly, I'm planning on using a home-built friction-drive arrangement. The GEBE setup most likely will not work on my bike, and I do not have enough room (I live in a 2nd floor appartment) for two bikes. Also, because I live in an appartment, I need to have a quick-detach system so I can put the motor out on the balcony and not need to worry about gasoline smells and vapor accumulations indoors.
  17. dbigkahunna

    dbigkahunna Guest

    Check on the Staton site. He has a Robin 40cc engine used for generators that would make a spiffy direct drive friction drive bike. I have on of these I am looking for a bike to set it on. CarrPresision Engineering has some plans for using a weed wacker to make a friction drive set up. The plans cost seem to be reasonable. Keep us informed on your progress.
  18. prism

    prism Guest


    1) the 'Burd', complete with clutch, was donated as a
    'Christmas present'. Best one of those I ever had.
    2) have all the bearings, some chain, throttle cable, some hardware,
    chain tensioner parts, etc.
    3) Need to get the aluminum so's I can start cutting metal, which brings me to issue four:
    4) someone wants me to assemble a 'Happy Time' engine for him and then fit it to the bike. Of course, the thing will need some break in... This leaves me with one obnoxious question:

    Just how do you remove a badly-made nut that's shaped like a circle with five randomly-filed half-round notches in it? The reason: there's a lot of what looks like chewed-up clutch material in the gap, and that scares me to death.

    thanks in advance for any comments. I've got a camera now, so I'll be documenting my findings as I go, along with drawings as needed. (It will take a while, as I'll finally need to replace a lot of the tools I lost in that 2002 car crash.)
  19. Esteban

    Esteban Active Member

    Friction drive bike motor kits have been around forever, & do NOT devour tires. The rider has to learn how to operate them correctly & accelerate slowly. Proper roller pressure on the tire i & inflation is a must as well.
  20. duivendyk

    duivendyk Guest

    To my mind it all boils down to: Do you need substantial all-weather hill climbing ability, if so rollerdrive is prob.a bad idea and chain or belt drive would be preferable IMO.