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| *Vultures Knob>>>Bike Pedals |
I put a 49cc motor on a bike and it works just its not very fast. What am i doing wrong? |
I put a 49cc motor on a bicycle. i took off the pedals and put the sproket that came with the motor where the left pedal used to be. That way the motor does what the pedals used to do. i kept all of the gears on the bike like it had originaly. It works good. The motor and everything is lined up and it runs. It just runs very slowly. I have to push off to get it going(which I expected I would have to do any way). I have the bike in the very first gear. It just doesn't seem like it is able to get the bike up and going. After I get the bike going by pushing with my feet it will go on its own just not very fast. I am not sure as to what condition the motor is in as i bought it as a pocket bike off ebay and it has never really ran great. Is there anything that i need to do differently to get it to run better or do I just have a bad set up? Any help or suggestions is greatly appreciated. Look on the Bright Side,Willy......... If You ever get it on a long enough straightaway,, in a Couple of days you'll have a 400~500 Mph Bicycle :) ................................. Seriously,,, Gearing is a Crucial aspect of setting up any engine in a vehicle. Ideally,,,You should Know *the engine's RPM range,,,, and *the RPM where it makes it's peak Torque. Then Calculate the gearing accordingly ................................. GEARING is seen by the Engine as WEIGHT,,,a LOAD. Your bike is geared so High it's trying to do Exact same thing as Pull the weight of a couple of cars,,,,or climb Straight Up a wall. A very basic explanation of Why that works that way.... *Engine makes 1 Power Impulse each time the spark plug fires. ---on a 2 Stroke,that's Every time Piston goes Up ---on a 4 Stroke,,it's every OTHER Time. * Important Also to understand that Engines make VERY WEAK power Impulses at Low Speeds. The Strength of Each Impulse gets Stronger as engine speed Rises. Now imagine we have a bike geared 1:1,,One to One. That means for Every Complete Revolution of the Engine, The Rear Wheel also makes ONE Revolution. If it's 4:1,,,4 to 1,,,, Engine turns 4 Times,,Wheel Turns ONE. That's how it's usually Taught,,,and that's what you'll often hear folks Repeat to "explain gearing". But what's just as important to understand is the Effect of the POWER IMPULSES delivered to Rear Wheel through the Gearing. If we had 1:1 Gear Ratio,,, How many POWER IMPULSES get applied to Wheel,,,,each time the WHEEL makes one full turn? That's RIGHT,,,,,ONLY ONE. But That ONE Power Impulse from the Engine does not LAST "Full Circle". At BEST it's only HALF-CIRCLE. And In Reality,,,,it's Only EFFECTIVE for about 1/3 to 1/4 of a Circle. Picture Youself turning the wheel by hand against a Load. You pull the wheel for about 1/4 Turn then Quit. The wheel is "Dead" as far as Receiving Power for 3/4 of the Full Turn. Now REGEAR it to 2:1. That means engine applies 2 Power Impulses per Wheel Revolution. It Pushes the wheel starting at "12 Oclock" and Quits at 3 o'clock. But it starts AGAIN at 6 Oclock and pushes till 9 Oclock. Not ONLY is it Now getting 2 Power Impulses instead of 1. And only being Pushes 1/4 of a turn & Dead for 3/4 Turn It's Now getting 2 1/4Turn Power Hits,,,for a Total of of HALF a Turn under Power. Instead of just 1/4 Turn under Power. And it's now "Dead" only Half a Turn,instead of 3/4 Turn Dead with No Power. Lets gear even LOWER,,,to 4:1 Now,,,Every 1/4 Turn it gets a Power Hit. But MORE than that,,,,the Wheel is no longer ever "Dead". Because after the 1/4 Turn that the Power LASTS,,,, As it's fading Away it gets a NEW Power Hit. So Wheel is Under Power for a FULL TURN. The Power Impulse RISES & FALLS as each impulse Begins & ends. It's NOT Steady. But it it's PRESENCE Lasts 1/4 Turn,,,, At 4:1 Gear ration the Power Impulses Begin to MEET and Overlap each Other. If You Charted the Power OF The Wheel,,,it would be A Spikey,Wavy Line. Showing Power Rise and Fall. But at 4:1 Ratio with a 1/4 Power Impulse Duration(in this example anyway)..... The Impulses Overlap and the Power Chart would show that the Wheel has NO "Dead Spots". It would never Coast,,,it would Always be Under Power. Lets Double it again,,,to 8:1 8 Power Impulse per Wheel Revolution. That's Applyiing Power every 1/8 of a Wheel Turn. Seems Odd,,,If A Single Impulse LASTS 1/4 of a Wheel Turn,,,How can it apply Power every 1/8 Turn? The Gearing Relationship begins to COMPRESS the Power Impluse into a SMALLER DEGREE of Wheel Turn. Instead of spreading it out over a larger amount of wheel turn. Lets say the wheel has 36 Spokes. A Full Circle is 360 Degrees. So the Distance between 2 Spokes is 10*Degrees At 1:1 Ratio,,,where power impulse lasts 1/4 Engine Revolution, The Power is spread over 90* Degrees. 1/4 Turn is 90*. 4 x 90=360>Full Turn. Keeping in mind a 36 spoke wheel has 10* Space/Distance from Spoke-to-Spoke,,,, 1/4 Wheel Turn =90* = "9 Spokes worth" of Distance as tire rolls across ground. At 2:1 Gear ratio,,, Total Power is "Compressed" into 4.5 Spokes' distance as wheel rolls across the ground. 4:1 ratio = about 2.25 Spokes 8 :1 ratio would put Full Duration of Power Impulse onto about 1 1/8 Spokes Distance 9:1,,,EVERY Spoke gets a FULL Power Impulse concentrated on it Beyond 9:1,,,,Power Impulses begin to Overlap. At 18:1,,,each spoke would get 2 Full Power Impulses. Easy to Imagine the Difference in PULLING POWER between: a) ONE Impulse spread over 9 Spokes b) 2 Power Impulses PER SPOKE So Lower Gearing Compresses/Concentrates More Engine Power Per Degree of Wheel Rotation. Wheel gets "More Pulling Power". The Trade-Off is WHEEL SPEED. at 1:1 the Engine Turns at Same Speed as Wheel. at 10:1,,,Engine Turns 10 Times,while wheel turns only Once >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>... How to estimate what Gearing you NEED Bicycles are a nightmare of Tire Sizes. A 26" Bike Tire can be near 24" or 27" Same for 20's,24's,etc. Let's use 26" Diameter. Who knows how fast engine will turn,,or where it's PEAK power is,,Or where it BEGINS pulling? Not me,for sure. But we can "Think Backwards" by being familiar with some of the average speeds that 26" Bikes Go with motors . Which is about 30~35 Mph. Lets use 30 Mph,,,because that will result in a Lower Gearing>Better Pulling Power. And in my opinion anything over 30 mph on a bicycle is Foolish>>brakes,wheel bearings,tires,steering geometry ,etc were NOT designed for Hi Speed. So for a 26" tire to go 30Mph,,,,we STILL need a 3rd variable. Either Engine Speed or Gear ratio. Most Small Engines like Yours should run about 6,000~7,000 RPM We can GUESS it's 7,000 For a 7,000 engine to make a 26" Tire go 30MPH 16:1 = 34 mph 18:1 = 30 mph 12:1 = 45 mph A 20" Tire going 30mph @ 7000 would need a 14:1 ratio. >>>>>>>>>>>>>>> All those Ratio Numbers are in the realm of LOW/1st Gear on Car/Bike Transmissions with 4,5,6 speeds They are "Impossibly Low" for Direct Drive. Meaning,,,a Sprocket on Engine going directly to Sprocket on Rear Wheel, At 14:1,,,,16:1,,or 18:1 , A 10 Tooth on Engine would need a 140,,,160,,,180 Tooth Wheel Sprocket. I dunno if such things are even made. A BIG rear sprockt is 50~60 teeth. A SMALL front one is 10 teeth. That's 5:1~ 6:1 Even the Lower/Slower 6:1,,,,even with a Small 20" Tire,,, That calcs to 70mph. With a 26" Tire? 90 Mph!!! The Engine would Never Pull That sorta gearing to that speed(thankgawd) Plus it would accelerate TERRIBLY slow. ................................. The Solution to get the OVERALL Gearing LOW Enough,,,down into 12~14~16~18:1 ranges requires Splitting the Ratio by using a Primary Reduction. A "Gear Box" or Primary Drive,,or Jackshaft,,,Intermediate Shaft. Which Sounds like what You have rigged up. But in effect,,it's "Backwards" It's severely OVER-Driving the back wheel. When it actualy should be "severely" UNDER-Driving it. SOME of those little engines DO HAVE a Primary Reduction Drive. Engine drives a Reduction Gear,,,>> and the Output of that Reduction gear>> then drives Rear Wheel. If we keep the 26" wheel,,30mph,,,,7000 rpm example That requires an estimated 18:1 ratio. Engine Turns 18 times,,while Rear Wheel turns ONE time. Ok,,,that would need a 10 tooth Engine sprocket and a 180 Tooth Wheel Sprocket(No Such Thing in reality) But ,,,18:1 = 10T x 180T. By Using Primary Reduction,,,we can change Gear Tooth Count to some Realistic(and obtainable) Sprocket Sizes. Lets say we Know we can Easy & Cheap get a 50 Tooth WHEEL Sprocket. And we have a 10 Tooth OUTPUT SHAFT Driving that 50T. That gives us a 5:1 FINAL DRIVE between Output & Wheel. We need to SPLIT that 5:1 Down to an OVERALL Ratio of 18:1. 18 Divided by 5 = 3.6 So we need a 3.6:1 Primary Reduction between Engine and "Intermediate Shaft" ---Output Shaft. A 10Tooth on Engine ,, Driving a 36 Tooth on Shaft would be 3.6:1. So Shaft would be turning 3.6 times Slower than Engine. But Also,,,Engine would be Applying Power Impluse "3.6 TIMES" for every SHAFT Turn. 36 Engine Power Inpulses to Shaft ,,every 10 Shaft Turns. Ok,,,,ALSO on the Intermediate Shaft is ANOTHER Gear . The OUTPUT to Drive the Back Wheel. That OUTPUT Sprocket is "10 Teeth" Those 10 teeth Drive Rear Wheel's 50 Teeth. So there's a Primary Reduction of 3.6:1,,,, 10 Tooth Drive x 36 Tooth Driven. And That is OUTPUT>DRIVE to a Final Drive Ratio of 5:1. 10 Tooth Drive x 50 T Driven. 3.6:1 x 5:1 = 18:1. Engine Turns 18 Times in order to turn Wheel 1 Time. Engine 10T>>>IN Shaft 36T xxx OUT Shaft10T>>>Wheel 50T You can Juggle Sizes to enable using what Gears you Have,,,but yo still need to Focus on OVERALL ratio Like: 10 x 36 Primary into a 10 10x 50 Final = 18:1 Overall You could use a 14 x50 Primary into a 10x50 = about 17.85,, close enough Or,12x 30(2.5:1) into a 10x72(7.20:1) =18:1 Or,,10 x 40(4:1) into a 12 x 54 ( 4.50:1)= 18:1 ................................. The Ratio Formula is Simple. "DRIVEN gear divided by DRIVE gear = ratio" Example: 10 T on Engine & 40 T being driven by that. 40 -/- 10= 4:1 Same goes for rear wheel. Drive divided by Driven. A 12T Output Shaft driving a 48t Wheel sprkt. 48 -/- 12 = 4:1 Multiply the PRIMARY DRIVE RATI0 (Engine to shaft) by the FINAL DRIVE RATIO (Shaft to Wheel) This example would be 4:1 for Both. So,,,4 x 4 =16:1 OVERALL RATIO ................................. Here's a calculator to estimate Speed. It input fields for * RPM-Engine Speed *Tire Diameter *Axle Ratio (Which is FINAL DRIVE) *Transmission Ratio * Transfer Case ratio On Transfer Case or Transmission,,,, Consider Either One to be "Primary Drive". Doesn't matter which. USE the Ratio between Engine & Shaft. Enter 1 in the OTHER box. 1 equals "zero"---NO ratio change. Example: * RPM-......7000 *Tire Diameter.......26 *Axle Ratio (Which is FINAL DRIVE),,,,,(6:1),,enter 6 *Transmission Ratio.......3:1,,,enter 3 * Transfer Case ratio ,,,always enter 1 Result> MPH = 30.xxxx MPH Any Factor You Change will Change MPH. Smaller Tire=Slower Faster Engine RPM = Faster Larger Ratio Numbers =Lower Gearing = Slower In Your ACTUAL case,,,I'd suggest using 6000 or 7000 RPM. And finding a set of ratios which yield around 30~35 Mph MAX http://home.comcast.net/~jobrated/calula... That's Just to help you select gear teeth count in order to end up with something in a realistic and useful range. Small on Engine >to Bigger on Shaft and in combination with Small Output gear on Shaft>Bigger gear on Wheel. ................................. A while back I was looking at "Bicycle Engine Kits". Scroll down and look at the "Rear Sprocket & Drive Adaptor" "Sprocket Mounting hardware" (the whole sight may also give you some useful ideas). That Sprkt Mounting puts gear on LEFT Side. And a 50T is still way to small to run Direct from engine without any primary reduction.. But just as an IDEA,,,you Could set it up to use a "jackshaft" Between Engine and Wheel. Which would take some creativity And some fabrication. But You'd have both IN & Out sprkts on the shaft,,on same side (Left) and spaced close together. http://www.kingsmotorbikes.com/bicycle_p... Here's more pics for rear sprocket mounting http://www.kingsmotorbikes.com/fa_q.htm... ***Those engines have Clutches with a "built in Primary Reduction",,,,which is why the Final Drive Gears are not outrageously Huge //////////////////////////////... There's a Bunch of ways to ACHIEVE the Primary reduction you need to reach realistic Overall ratios. Limited only by one's imagination,finances,and facilities. However you go about it,,,, I would NOT target over 40~45 mph Max, 30mph is Much more SANE. 50mph would be Great Fun,,,, but a Frame breaking into 2 Pieces at 50mph = GAME OVER. NO FUN. They can break at 30mph just as easy,,, but you Might survive it at 30 .............................. With a 26" wheel you need an OVERALL ratio in Mid-to-Hi Teens. 15:1 to 20:1 i'd guess. A 20",,,you need low to mid teens 10:1~15:1 range Calculate Engine-to-Shaft and Shaft-to-Wheel,,,then multiply those 2 together. Juggle any tooth combo you want to,,,as long as your OVERALL ratio comes out within range. I dunno if any of that makes sense,,,but hopefully it'll help get you pointed in the right direct. It's a complicated task to get it Physically set-up. Good Luck! Is there a clutch adjustment that can be made? I bet it doesn't have a clutch. My guess is that the gear ratio is out of whack. Is the rear sprocket on the bike like 10 times larger than the pocket bike rear sproket? I would look at that first. You need lower gearing. get the biggest sprocket that will fit for the motor side of the pedal and the smallest you can find for the motor. The tires on a bike are 4 times bigger than the pocket bikes so the gearing is way to high. You can also change the bike gearing, smaller on the crank and larger on the rear wheel. good luck sounds kike a gearing problem to me also why not run it straight to the rear sprocket? think you gota gearing problem. what size it the left side sproket..it should be about the same size or larger as the one that the bike came with ==rule of thumb===1-2 inch sproket on the motor =to= 5 or 6 inch sproket ...this will enable the motor to turn at its normal rpm range...having too large of a sproket will cause the motor to lug....bob you have answered your own Question *it never really ran great" puting a bad engine in a differant frame will not fix it (LOL) how slow is slow ? what is the weight ratio ( u+b+e=Y). you have reinvented one of the first motorized bikes, they were all like yours (congrats (I am not being Sarcastic with the congrats)) look at early bikes they kept the pedals and the first tex=PA Pedal Assisted. I like bikes my quote "I would rather ride your motorize bike than push a Tractor (hardlydavirson=american anchor) all spelling is down to the folt with the computer. Rearguards & Watch yer back, Scouse Dave |
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