46CC for 60 MPH

i was looking into a shift kit it seams like it makes a good bit of difference when you ride i just dont have the cash for it which sucks i wish i did my project would be so much further along than a engine in a box in the corner

bowljoman said:

I figured air-resistance for a cubed function.

Also note.... If you are using my original imput numbers, I am under 200lb's total mass including scooter.

So your numbers wont work for someone else. Both engines Im using are the same mass.

Hrmmmm by your calculations it sounds like I could lower the ration, and spin my old engine up to a higher RPM for potentially more speed.....

interesting... I may try that too!! Thanks guys. I know 60 is possible because Go-ped riders can port their r46 engine's and spin them up to 14000 RPM to get there in a single speed set-up.

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The numbers for air resistance will work.

The subject of mass does not play a role in air resistance; now, in rolling resistance? Yes. Weight plays a massive role in rolling resistance; in fact, it plays one of the biggest roles in rolling resistance.

Also, yes, you ca indeed spin your old engine up a higher RPM to achieve what you want; you will however need to compensate by having a different gear ratio to accomodate.

elemein said:

That may be a rule of thumb and a simpler way to look at it, but that is not the most precise or correct way.

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The most precise way is just blowing smoke because there are so many factors. Air resistance is a function of velocity squared, so in order to provide enough power to match air resistance at double the speed it usually takes about 4 times the torque. HP being a function of torque at a given rpm, HP is directly related to the maximum air resistance force which can be overcome for acceleration.

Based on what pocket bikes with much smaller frontal areas and better aero can do with a CVT 50cc and a long stretch, I think 50mph is totally possible with about 5 hp, but to hit 60 its gonna take much more power to overcome the wind. If you overdrive it it will lose so much torque that it will probably slow down.

It will be cool to see how fast a high strung 50 goes with some gears. To get 60mph it's gonna require dusbin fairings or something. Maybe I'm wrong.

Weight can play a factor in top speed because the heavier you are, the more speed is scrubbed with every bump you hit. Suspension will make your bike go faster if it floats well. Weight also affects how much friction occurs at the bearings which saps power. Standing up and taking weight off the rear axle of my electric MX makes it go up hills faster by reducing friction.

The 110cc 6hp Lifan super pocket bikes with 4 speed manual with lots of torque will top out at 50 mph. I would expect with another 3 hp 60mph would be achievable.

You can get big power out of a 50cc, 10+ hp if you tune it right. I think one of the geared 3 speed hubs can hold at least 1.5 hp from experience with a 1000 watt electric motor and breaking stuff in and on the IGH. A china definitely be okay on a geared hub, when you approach 4-5 hp it's iffy. I'd like to use a IGH jackshaft for a 50 2 stroke, it's gonna be close with the maxing out of the hub. The planetary gears are tiny, so I wouldn't expect them to handle 5 hp for long. Some of the new geared hubs are pretty cheap, so if you made it a regular service item like a racing gearbox, it wouldn't be an issue. If you're rich you could just swap them out like $100 cartridges and never open them up.

Whether this would work on an everyday bike, sure as long as you take it easy. There are so many weak points at least in the Sturmey hubs, like the cog, the driver, the right hand ball ring, the cable adjustment, the cone adjustment, the lube level, shock loading, it can be a pain in the ass to maintain and keep from crapping out because one thing will lead to the next so quickly and frak the guts. NEVER get wheel hop or the pawls will shatter, believe me. Some sort of drive damper to the hub driver would reduce a lot of the shock loading that will eventually kill any motorized geared hub.

I definitely like the idea of using the hub as a jackshaft because it's easier to replace the unit when it eventually dies, since you don't have to re-spoke the whole thing, or replace the innards.

Keep up with this, I'm definitely down with the idea of making light efficient bikes since the big chunky motors don't seem very befitting for what I'd like to use for frames to start with.

I don't see how an IGH can be more efficient than a CVT unless the belt is slipping. There is virtually no drag and the CVT remains smooth even when heavily loaded. At least what I've witnessed with IGH's is that you can feel the gear drag in anything but direct drive. The expensive ones must be better like the Rohloff speed hub. I would think that if it was tuned right, a CVT would make the bike go faster, that's the case for when they're installed on pocket bikes, because they shift constantly, keeping the little motor in its powerband all the way until reaching about 3:1 reduction in high. Such top speeds aren't achievable without keeping the engine at peak power all the way through a pull to allow for a taller final drive ratio and a higher top speed. People only complain about the drag of a CVT when the variator isn't tuned for the powerband.

You'll want to take the dynamo hub off the scoot, it causes some drag.

The bearings in my scooter wheels installed on my Razor Mx1000 are practically new, as are the wheels. The fact is, when you're trying to go fast with little power, frictional losses (tiny as they may be) can add up to a couple mph, as they do hillclimbing on my terribly underpowered electric bike. Running larger wheel, like on a road bicycle will decrease frictional losses, and that tiny rear wheel spinning really fast is a source of drag.

A road bicycle would make your goal so much easier, they'll do 50mph with a 1.5 hp China Girl run single gear. I don't quite understand your obsession with speed yet aversion to horsepower. It's interesting anyways. If you have any recommendations for bulletproof hubs please share because they're always sought after here.

CVTs are only good for engines with 5.5 HP or more below that and the friction it has from the belt getting pinched by the rear pulley the 99 predator has a lot of trouble running a CVT so a jack shaft will put preform it its after the 5.5 hp mark that they start to do good because they start at around 2.5-3:1 and work up to a overdrive and the reason a pocket bike only does 50MPH is the tiny tires compared to a bike

I think the confusion is that you're saying all CVT's are the same. The pocket bike ones usually always make them have higher top speed capability. It's a fact.

Just because your particular CVT didn't work didn't mean there aren't others which are better. You're going to need acceleration potential, because going 60mph after building up speed for a mile seems quite dull. Most sub 50cc pocket bikes make less than 4 hp, and the CVT is an effective transmission for their high revving powerband that is normally just a short moment with traditional gearing. If you're not in the powerband, you're not making that maximum power number you'll need to accelerate through air and rolling resistance. The particular CVT I'll be using on a sub 50cc 60mph (hopefully) noped dirtbike starts at 7:1 and goes to 3:1. If you have one that goes into overdrive there will never be enough torque. The Cagllari I've got supposedly is good for around 11,500, the thing is, will it have enough torque to actually accelerate through final gear. Like selecting gears for a particular race track, you want the engine to be maxed in top gear at your theoretical top speed or in your case, your desired top speed. That way you won't be over or under geared, which will matter a lot.

Lowracer says his mountain bike with a single speed stage II Cag would do 50. I figure with the CVT multiplying torque and the proper final gearing 60 should be realistic. It realistically makes about 4HP, and with a racing clutch and the CVT it will be constantly belting out max power from a stop. Work is the total power applied over time, and if you can apply more power per unit time over a period of time, then more work is done. More work done over time is power - hp - so you're putting more power to the ground through a CVT than with a normal box where you need to run up through the gears. This is most important with small high revving engines that just won't pull if they're overloaded. The cure to this with fixed ratios is to use more splits. That would mean using a IGH with more gears, more fragile, more pause in between gear shifts where momentum is lost.

I don't quite get the point of the arbitrary limits you've set forth for yourself in hardware, which is in opposition to your speed goal. It seems illogical to me to take anything off the table that would make a faster, more fun goped, but obviously its more of a personal challenge for you so. I'll graciously back out of this, I really shouldn't have responded in the first place since it was pointless and you've got some set guidelines you've predetermined. I hope it works out, please post your results and gear ratios when you get it figured out.

Go for the most expensive strongest hub you can buy, with as many gear splits as possible. I think that will enable you to achieve all of your goals of torque and top speed, a 3 or 5 speed might not have the spread you're looking for. Shimanos have more gear spread than SA's so better for climbing, but SA's are good for bikes with power because there arent gears too closely spaced to waste time pausing to click through.