49cc engine

[Ghanem]

Hey guys i have a 49cc engine, How can i calculate the RPM??

Thanks

 

[Russ2251]

Can't. Must be measured.

 

[r97]

If you have either:

A. the torque and hp ratings

B. all gear ratios, top speed, and the rear tire size

We could get you an approximate, but neither are nearly as accurate as simply measuring with a tachometer.

 

[j.concepcion54321]

OR if you have a model number we can use a secret tool that we have called "google" and find the specs of that engine and let you know.....

 

[Ghanem]

its a chinese engine and i want to mount it on my Bmx but i want to know the gear ratio first i saw the site http://www.csgnetwork.com/minibikepotentialspeedcalc.html
Drive Wheel Diameter In Inches 19
Rated Engine RPM ???
Teeth On Axle 6
Teeth On Clutch 20

 

[Ghanem]

please reply

 

[jman231994]

Patience. Don't forget time zones, it's probably midnight in the states or something?

 

[Ghanem]

if it is midnight why are you on the forum

 

[jman231994]

Haha I'm in australia. It was only early afternoon for me. Everyone else that had posted seemed to be from America. I have no clue if its midnight or not but it makes sense. There doesnt seem to be much going on on the forum at all atm.

I could have a shot at the calculation to work out a rough rpm like r97 said. But to do it working backwards like that I will need a top speed for it, which since you havent built it will be kind of hard for you to get hahaha.

What I can say though is, Shouldnt the teeth on the clutch be 6 and axle 20? I think you got it back to front. Either way your going to need a bigger rear sprocket if you intend to drive a bmx wheel. Try for a 6:1 ratio at least, I think.

When everyone else comes on they will give you a much better guide on all that stuff. I know bits in theory but not so much in practice.

Good luck.

 

[Ghanem]

Thanks

 

[Russ2251]

Going to need a jackshaft arrangement to accommodate a 19" diameter tire.

 

[j.concepcion54321]

a typical one goes around 6000 rpm

so with that stuff you would be going around 100mph and itd take you roughly 10 minutes to get there.

yeah you needa a jackshaft

 

[Ghanem]

can't i put the chain from the engine sprocket to the rear sprocket?

 

[Ghanem]

Thats the same engine i have

 

[Russ2251]

can't i put the chain from the engine sprocket to the rear sprocket?

Did you ever try to pedal a 15 speed bicycle from a standing stop in 15th gear?
Now, imagine the strain on that itty bitty clutch.
Would make for a good cigarette lighter.

 

[augidog]

that's a "Cagllari" pocketbike engine and it's a 47cc case-inducted 2-stroke that hauls pretty good but won't last very long at WOT...run a high oil/gas ratio to protect inferior parts.

i ran a cag47 on my 26" bicycle (Golden Eagle belt-drive) at an 18:1 ratio and did high 30's. the cag will do 9000+ but i recommend running it steady at 5000-8000.

to make a 30'ish mph 20" bicycle, you'll need about a 15:1 total ratio from crankshaft to rear hub. to do it in one step would require a rear sprocket near as large as the wheel itself. you'll need some reduction elsewhere.

and wear a freakin' helmet already...

at 30mph, your 20" cup & cone bicycle wheels will be spinning at 8.4 revolutions per second!

 

[Badot]

The nice thing about putting a motor on a bike is you can gear it rather high... if you pedal it up to speed.

My motorbike runs a HF 2.5, to a 10T clutch, straight to what I believe is a 56T rear sprocket bolted to the wheel. 40mph @ 3600 RPM, 25 at clutch engagement (2200?). Acceleration is piss poor with only the engine, and I'm sure it'll burn up the clutch very fast if I tried. But even somewhat gentle pedaling assisting the engine makes it seem extremely fast off the line.

BUT... 2 strokes run at much higher revs than 4 strokes, so you're going to need probably at least 3x the reduction that I used.

 

[augidog]

The nice thing about putting a motor on a bike is you can gear it rather high... if you pedal it up to speed...

But even somewhat gentle pedaling assisting the engine makes it seem extremely fast off the line.

spoken like someone who's into it. my MaB makes me feel like superman.

personally, i love the man & machine parameters...i'm completely stoked about fine-tuning my pedal and assist ratios after i tie in my cvt, i'm expecting good results.

speaking of on-topic...yes, the 2-strokes rely on rpm's for their power. my Tanaka 47R makes 2.8HP and is built to handle 11,000 rpm's, under load she'll pull up to about 9k & do it all day.

Ghanem, there's a 3.25:1 transmission that fits the cag...you have to do some research & choose your parts, but a final 4-5:1 reduction from the tranny to a rear sprocket is way doable.