Clutches are confusing

95Viper

It is amazing how complicated the clutch / belt setup is on these carts. I have an EZGO with a Honda24hp conversion. I have the stock clutches and will be converting to a Cvtech primary a week.

Last week was spent internet searching drive belts. Different widths, shorter lengths causing more torque, longer lengths possibly riding higher in primary clutch and giving more mph. Dozens of combinations to try.

Then to the secondary clutch. 36 degree or 28 degree. At first I thought this was the angle on the face of the clutch where the belt rides and people were machining them on a lathe. Now I read about torque springs and different holes that they can be mounted to increase the tension, 28 or 36 degree cams, shims.

Of course, all of these choices depend on what engine you have and what you want to do. Pulling, climbing or high speed. All of it is a heck of a lot more complicated than originally thought.

BGW

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LURCH

If I was you I would call CPP or Plowmans and tell them what you have and what you want to accomplish, see what they have to say and then make up your mind and do it. I wish I had done that last year when I started my build. You end up just doing it once instead of 2 or 3 times. Hope this helps, LURCH!!!!

95Viper

Thanks. I am lucky because I have Fstg21 here locally and educating me. He knows everything and has a machine shop. I am just absolutely amazed at how many variables there are. For instance, to get torque some just shorten the belt but that would have to lose top end mph because the belt will ride lower on the primary. Others use a 28 degree secondary, others a torque spring in secondary. I don't find many totally replacing the secondary on EZGO's.

I will test and measure my speed after each change and post it here.

fstg21

Ok, so with a BB you should only use the 36 degree helix. You have plenty of torque.

The spring preload on the Driven determines when it shifts out to the higher ratio.

The stiffer the preload, the longer it will stay in a lower ratio.

This can help in getting a large tired, heavy cart rolling. With a BB it is less of an issue.

If you find that while riding the engine tends to bog down severely while climbing grades, increase your preload to get it to downshift faster.

The equation for determining belt length is:

L= ((2*a*D2+2*a*D1)*Pi+D2^2-2*D1*D2+D1^2+8*a^2)/(4*a)

a=the center to center distance (distance between the center of the bolt holding on the drive and the bolt holding on the driven.)

Pi= if you don't know what this is, where in trouble.

D1=The Diameter of the drive clutch with the belt wrapped around it. Measure with a cheap dial caliper.(the belt is important because all belts are measured by the outside circumference not the inside)

D2= The diameter of the Driven Clutch with the belt wrapped around it. An easy way to measure this is to take it off the cart lay it on the concrete and mark it's diameter (with the belt on it) with a pencil then measure the distance between the marks with a tape.

So assuming I can do math(questionable)

Lets do a hypothetical:

(These aren't real numbers, so your mileage may vary.)

a= 14"

D1= 2"

D2= 9"

((2*14*9+2*14*2)*PI+9^2-2*2*9+2^2+8*14^2)/(4*14)= 46.15 (assuming no slack)

252+56*PI= 967.61

81-36+4+1568=1617

967.61+1617=2584.61

2584.61/56= 46.15"

If that makes sense.

To figure out the amount of slack you want
You use right angle triangle Theorem.
In this same example scenario:

B = the opposite leg of the triangle

a = our center to center distance still.

C = the length of the belt between the pulleys

S = the amount of slack you want

Y = is one half of the extra length needed + (C/2)

X = the extra belt length needed for the slack you want.

(D2/2)-(D1/2)=B

4.5-1=3.5

a^2+B^2=C^2

14^2 + 3.5^2= 208.25 sqrt of 208.25 is 14.43 14.43=C

Then to set slack:

(C/2)^2+S^2=Y^2

(14.43/2)^2+1^2= 53.06 sqrt53.06=7.284 Y=7.284

2Y-C=X

2(7.284)-14.43=.138

X+L=Total Belt Length Needed .138+46.15= 46.288

It only takes a .138" longer belt to add 1" of slack over a 14" center to center.

If I hadn't done the math I wouldn't have believed it.

fstg21

Now, here is the fun part.

Using this you can figure out if your driven clutch can open enough to support a bigger Drive clutch.

You just go backward with no slack.

The easiest way to check that is add the largest size on the drive to the smalles size on the driven.

For a simple example, at rest the Drive is 2" and the Driven 9"

Assuming you have an 8" drive clutch and the driven goes down to 3" with the belt around it when fully open.

They both equal 11. You starting point is the same, then your belt length is correct.

Now, if the driven clutch only goes to 4" when fully open then you are starting at 11 and needing 12.

To figure out how low the belt will ride on the Drive clutch wide open you take:

(D1+D2)Pi is the circumference of the pulleys.

(2+9)Pi=34.56

(4)Pi=12.56 for the smallest the Driven can go.

34.56-12.56=22

22/Pi=7" the max diameter the belt will ride up the Drive clutch

This assumes no stretch and no slack.

fstg21

Isn't Math Fun!!!

DOOmsman

What would 120 degrees more pre wrap do?

fstg21

Cause the driven to shift out at a higher speed. I can't give you specific numbers.

army

If I have to get into math like that I'm sticking with trial and error. Until I hit my VISA limit anyway

fstg21

It's actually really easy just punch in your numbers on the calculator.

ooh, we should create a calculator for the forum like the top speed calc.