math help, gearbox equasion,

Dang that kind of math is making my head hurt. .................

Hi Linnin, I do not have a box in front of me they are packed in the storage.

Take the small gear on clutch and divide it into the bigger gear it runs in, save that number: (A)

take the gear on that shaft and divide it into the number of teeth on the gear it drives, save that number (B)

take your output sprocket and divide it into the rear sprocket, save that number. (C)

now multiply (A) times (B) and the result times (C)

NOW that is your total gear ratio (final drive ratio).

RPM vs Speed?

now you got to do the circumference of the rear tire, and figure out how far it travels (how many revs for one mile)

Or just cheat and use a calculator like I have on my page here Simpson Motor Bikes

(expect a PM I need to figure shipping)

Mike

42, it's the answer to life, the universe and everything.

He is wrong anyhow linnix13 -

Doing the hokey-pokey is what it is all about!

Hi Linnix13,

Here are a few numbers you might find interesting. All the numbers are from the EZM Q-Matic prototype bikes. Speeds & RPMs supplied via electronic speedometer & tachometer. The stock ratio also verified on Dyno tests. The test were conducted using the HS 49 CC 4 stroke motor after break-in.

Actual higher speeds were recorded but not with optional ratios available [12.3 X 1 @ 8000 = 50.3 MPH]. The high speed HS motor also used the EZM tuned flex pipe system, special K & N intake breather, and adjustable main jet. EZM does not offer the adjustable main jet or K & N filter, only the tuned flex pipe system. The K & N air breather is available via K & N dealers.

26" bike @7500 RPMs [165 lb rider]

Stock EZM ratio 14.68 X 1 = 39.5 MPH
Optional EZM ratio 13.31 X 1 = 43.5 MPH
Optional EZM ratio 14.07 X 1 = 41.2 MPH
Optional EZM ratio 15.52 X 1 = 37.3 MPH
Optional EZM ratio 15.97 X 1 = 36.3 MPH
Optional EZM ratio 16.46 X 1 = 35.2 MPH

Chances are your drive is between 18.5 to 21 X 1, depending on rear sprockets and or which series of gearbox and won't be able to reach the higher speeds of the EZM drive system.

18.5 X 1 = 31 MPH
21 X 1 = 27.6 MPH

Information on the G4 drive with the 5 X 1 primary and a 44 tooth rear is 22 X 1 [26.3 MPH @ 7500 RPMs], with 48 rear sprocket is 24 X 1 [24.1 MPH], and 56 rear sprocket is 28 X 1 [20.7 MPH]. The G4 ratios are based on the advertized 5 X 1 primary numbers.

Hope this information is what you are looking for.

If looking for Galaxy numbers & ratios either multiply by 42 or divide by 42 to arrive at warp speeds.

Have fun,

PLEASE NOTE THIS WAS DONE FOR A JACKSHAFT BUT FOLLOW THE FORMAT FOR OTHERS.

Ok i haven't seen this put together in 1 place so i'll start here.
We will take a deep look at speeds and Rpm's the best way.

Start with the Wheel and work backwards.

In order to hit the speed we want and not kill our motor and not peddle too fast we need to consider all these figures.

I have some math to do here and will post calculations soon.

Any help from other members is appreciated.

I will start with wheel RPM and ground speeds.

Wheel RPM TO GROUND SPEED.

26" WHEEL - .5" FOR squishing under pressure.

Circumfrance = 80.11061266653972 inches.

feet in a mile = 5280 feet

Inches in a mile = 63360 inches

# of wheel rotations per mile =
63360 / 80.11 = 790.91 rotations per mile

---------------------------------------------
Desired Take off Speed = 5 MPH
790.91 X 5 = 3954.56 rotations per hour
3954.56 / 60 min = 65.91 RPM
Wheel speed = 65.91 RPM at 5 MPH
---------------------------------------------

Desired Max Speed = 45 MPH
790.91 x 45 = 35590.95 rotations per hour
35590.95 / 60 min = 593.1825 rpm
wheel speed = 593.1825 RPM
--------------------------------------------

So that is a nice range.
Not that we need to go that slow or fast.
Just baseline calculations to show extreme
min and max wheel rpm.

The main thing to consider right now is what
is the slowest the bike can move when the clutch
engages without stalling the engine.

= Drive Gear RPM divided by Overall Gear Ratio
This = the required Wheel rpm to not stall engine.

example:
HT motor 4:1 ratio internal gearing
1000 rpm motor speed.

1000 / 4.1 = 243.9024 RPM of 10T Drive Gear

10T Drive / 36T Driven = 3.6 : 1 ratio

243.9024 / 3.6 = 67.75 RPM

This means if your wheel is not rotating 67.75
revoloutions in a min your engine will stall if it is
running at 1000 rpm

ENGINE RPM VS WHEEL SPEEDS AND GEARS.

I will use some standard Sprocket configs to
figure out where we want to start.

So lets say 32T is the largest sprocket we have
on the Rear Cartrige or Freewheel.
This will be our lowest gear we need to get 5 MPH
at just above engine idle.

Wheel speed = 65.91 RPM at 5 MPH
32T Sprocket speed = 65.91 RPM at 5 MPH

For the JACKSHAFT we need to figure the nessessary rpm
of the next sprocket.
Which would be the Crank Sprocket at the Front Freewheel
that the bicycle chain is on.

We will call it sprocket 2 = "S2"
Since it is available we will figure on 44T for "S2"

Gear ratio = 44 / 32 = 1.375 : 1

65.91 / 1.375 = 47.935 Rpm at 44T at 5 MPH

Now lets figure what our jackshaft speed will need to be.

Engine Rpm at takeoff = 1000RPM
1000 / 4.1 = 243.91 RPM

243.91 / 47.953 = 5.086 : 1 ratio

----------------------------------------------------------------------
Now things are a little more complex here because we have
1 speed for the Jackshaft and 2 gears on it.
This means we need to work out 2 ratios that get the
44T sprocket moving at 47.953 RPM.

We cant solve for 2 variables so we will have to pick 1 sprocket.
We will start with the 17T sprocket on the left side of the Jackshaft.
Because it is available.

17T / 10T = 1.7 : 1 ratio.

243.91 / 1.7 = 143.4764 rpm at the 17T and Jackshaft

143.4764 / 47.953 = 2.99 : 1 ratio. so lets say 3:1

We also have another unknow sprocket in the system.
The 2nd front crank freewheel sprocket is smaller than the 44T
For chain interference we want some clearence.

Now the 36T is used

36 / 3 = 12
So a 12T would be optimal with the starting speed of 5MPH

The 12T isn't available.

Chainring sprockets are easy to come by so we could go a little smaller
than the 36T or a little bigger than the 44T.

There is a 48T available.

11T is pretty close lets look at it.

36 / 11 = 3.27 ratio
143.4764 / 3.27 = 43.8765 RPM

44 / 32 = 1.375 : 1

43.8765 X 1.375 = 60.3301 rpm of wheel.

60.3301 X 60 = 6319.806

6319.806 / 790.91 = 7.9905 MPH
---------------------------------------------------------------

So after all that heres how the cookie crumbles.

WITH MOTOR RPM = 1000
10T drive at motor at 243.91 RPM
17T at jackshaft at 143.4764 rpm
11T at jackshaft at 143.4764 rpm
36T at Front Freewheel at 43.8765 rpm
44T at front Freewheel at 43.8765 rpm
32T at wheel at 60.3301 rpm

Minimum peddeling speed = 7.9905 mph

--------------------------------------------------------------------

Lets figure the max speed.

Tuned Engine RPM = 6000
6000 / 4.1 = 1463.41 rpm at 10T
1463.41 / 1.7 = 860.832 rpm at 17T
860.832 rpm at 11T
860.832 / 3.27 = 263.2514 rpm at 36T
263.2514 at 44T sprocket

So in the same gear the 32T at the rear wheel
263.2514 x 1.375 = 361.97 Rpm at rear wheel

361.97 X 60 = 21718.2405
21718.2405 / 790.71 = 27.46 mph

So the low gear range is from 7.9905 MPH to 27.46 MPH

Remember we can shift now.

High gear lets say = 11T its pretty std on freewheels.

Now things get easier.
44 / 11 = 4 :1

263.2514 X 4 = 1053.0056 rpm

1053.0056 X 60 = 63180.36
63180.36 / 790.71 = 79.90 mph

Wow thats all i can say.
If you had a long enough run you could get there.

Specified engine rpm = 4500
4500 / 4.1 = 1097.56 rpm at 10T
1097.56 / 1.7 = 645.62 rpm at 17T and 11T
645.62 / 4 = 161.25 rpm at 44T
161.25 X 4 = 645.62 rpm at 11T rear freewheel
645.62 X 60 = 38737.2
38737.2 / 790.71 = 48.99 MPH.
STILL VERY IMPRESSIVE.

WITH 24T REAR SPROCKET
161,62 X (44/24) = 296.30
296.30 X 60 = 17778
17778 / 790.71 = 22.48 MPH

-----------------------------------------------------
tUNED ENGINE RPM = 6000 RPM
161.25 X (44/18) = 394.16
394.16 x 60 = 23650
23650 / 790.71 = 29.90 MPH
-----------------------------------------------------

vERY EASY TO SEE THE EFFECTS OF THE JACKSHAFT.
THE UNANSWERED QUESTION IS HOW MANY RPM DO WE
REALLY GET WITH THE TUNED ENGINE.

AND EVEN AT 4500 RPM THE SPEED GETS PRETTY HIGH.

iTS A MATTER OF HOW QUICKLY CAN WE GET TO SHIFTING SPEEDS
tHE 79.90 WOULD REQUIRE 7 TO 8 SHIFTS.

PLEASE ALSO NOTE IT IS MOST LIKLY INTENDED FOR THE 36T CHAINRING
TO DRIVE THE REAR FREEWHEEL.

I CALCULATED THIS THE OTHER WAY AROUND WHICH MAKES THINGS ALOT FASTER.

TO CLARIFY THE 11t JACKSHAFT SPROCKET SHOULD NORMALLY GO TO THE 44T CHAINRING.
tHAT MAKES A 4:1 REDUCTION.

WITH THE 11T GOING TO THE 36T WE HAVE A 3.27 REDUCTION.

tHAT MAKES A BIG DIFFERENCE.

bUT DEPENDING ON HOW NUTTY YOU WANT TO BE.
I DON'T SEE WHY YOU COULDN'T RUN THE FRONT FREEWHEEL EITHER WAY.
iT'S A MATTER OF HOW YOU PUT THE SPROCKETS ON.

NOW I REALLY UNDERSTAND WHY THESE JACKSHAFTS ARE LIKE GOLD.
LOOK AT WHAT IT ACCOMPLISHES.

GENERALLY IF CONFIGURED CORRECTLY.
YOU WOULD NEVER NEED TO RUN THE ENGINE AT HIGH RPM

Best way to measure the true circumference of the wheel is to make the tire sidewall and the corresponding place on the ground and get on the bike and roll forward until the spot touches the ground again. measure between the two spots. This will give you a true reading with the rolling distance with the bike loaded and the tires compressed with the weight.

I think you have the record for the longest post !!!

RebelMoby said:

Best way to measure the true circumference of the wheel is to make the tire sidewall and the corresponding place on the ground and get on the bike and roll forward until the spot touches the ground again. measure between the two spots. This will give you a true reading with the rolling distance with the bike loaded and the tires compressed with the weight.

Click to expand...

A friend showed me a really neat trick when he insisted on calibrating my speedometer. Put a dot of oil on the tread, sit on the bike and roll it forward a ways, measure the distance between the dots on the ground and you have the true diameter.

Never oil your tires....only your brakes.

That was an inside joke, way inside, but I'll let you in on it.

One time I was working on my (then 8 year old) daughters bike. Using my DRY SENSE OF HUMOR when she asked what I was doing, I said "I am oiling your brakes honey." Then I showed her how I was oiling the chain, pedals ect.

Later, at a school program she stood up on stage and told the whole school "I know MY daddy loves me because he oils the brakes on my bike."

The whole auditorium was silent. Mrs. Joe started to giggle, and then so did I.

They all looked at us and then our daughter waved and said "Hi dad, hi mom." So they knew it was us, and we were laughing, nobody else was.

It looked really bad to the outsider, but it was and has always been a good family get together laugh.

Sorry for the long post but it really shows in depth how to figure out your rpms and speeds.

Dose it not????

Hi Linnix13,

When you reduce the numbers [ratios]you reduce to usable torque and increase the top end. Considering your system only has one ratio, it is best to arrive at numbers that run the motor RPMs at the speed you wish to "cruise". The HS motor is really happy between 5800 & 6200 RPMs, therefore if you normally ride at lets say 29 MPH [legal speed in many states is 30 MPH] you would want to make the motor turn at approx 6000 RPMs. If the ratio is 16 X 1 then you will travel at 29 MPH @ 6000 RPMs. The HS motor can quickly hit 7500 RPMs or higher if needed [always better to have too much power as not enough].

The other way to gear at numbers like 18.75 X 1 and you can watch your motor "sing" to reach 29 MPH [7200 RPM = 29 MPH] . It is much harder on a motor to run at high RPMs all the time, and we like using ratios to take advantage of the peak engine torque for a much smoother, quite, better MPG, and still have a little in reserve if needed.

I don't remember the internal ratios of the "Hoot" box, but it is easy to determine. Next time you open it to apply grease, simply count the number of turns of the motor [clutch bell] to make the output shaft once. Just mark and turn the clutch bell and see how many revolutions to equal one complete revolution of the output sprocket. Then divide the number of teeth on the output sprocket into the number of teeth on the rear sprocket.

You will find the only way to alter your ratios is the output sprocket and the rear sprocket, and your choices are limited.

Have fun,