gearing

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panhead55
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gearing

#1

Post by panhead55 » Sun Feb 22, 2009 11:54 pm

hello everyone. my panhead when in 4th gear feels wrapped out around 55. i am running a motor sprocket at 23, tranny at 25, and rear sprocket at 51. any suggestions on which numbers to run so i can take to the highways more easily? thanks, billy



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Re: gearing

#2

Post by mbskeam » Mon Feb 23, 2009 1:08 am

24/E 24/T or 24/E 25/E both work good. but 24/24 is good for a 74"

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Re: gearing

#3

Post by Cotten » Mon Feb 23, 2009 1:50 pm

panhead55 wrote:hello everyone. my panhead when in 4th gear feels wrapped out around 55. i am running a motor sprocket at 23, tranny at 25, and rear sprocket at 51. any suggestions on which numbers to run so i can take to the highways more easily? thanks, billy
You are already geared "tall" for the highway with that 25T countersprocket.
If anything you are 'lugging it', and not even into its powerband at 55 mph; A 74" motor geared that high shouldn't peak its powerband until twice that speed!

The motor can reach a point where the pulses blend into an 'aircraft whine', and still have throttle left for passing. The motors are designed to turn faster than the average rider's intuition.

If indeed highway speeds are uncomfortable, then I would suggest searching for causes of vibration, such as worn chains and sprockets, and other chassis issues. If it is just a matter of motor noise, it might need fixing.

....Cotten

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Re: gearing

#4

Post by 51Hog » Tue Feb 24, 2009 5:58 pm

Cotten wrote:
You are already geared "tall" for the highway with that 25T countersprocket.
If anything you are 'lugging it', and not even into its powerband at 55 mph; A 74" motor geared that high shouldn't peak its powerband until twice that speed!

What RPM range is the powerband?

The motor can reach a point where the pulses blend into an 'aircraft whine', and still have throttle left for passing. The motors are designed to turn faster than the average rider's intuition.

At what RPM does this 'aircraft whine' happen?



If indeed highway speeds are uncomfortable, then I would suggest searching for causes of vibration, such as worn chains and sprockets, and other chassis issues. If it is just a matter of motor noise, it might need fixing.

....Cotten
What RPM do you recommend at a cruising speed of 65mph Cotten?
Dale

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Re: gearing

#5

Post by panhead » Tue Feb 24, 2009 6:45 pm

Here is Jack Hester program on gear ratio's:

http://www.terra-glide.net/pgms/WheelSpeed.exe

VT

Re: gearing

#6

Post by VT » Tue Feb 24, 2009 8:28 pm

For low rev's in 4th gear at 62 mph, use a 24-T motor sprocket, a stock clutch hub sprocket and a 25-T trans sprocket with the 51 tooth rear (stock) rear wheel sprocket.
If you want it taller and less rev's than that, use a 26-T trans sprocket instead of a 25-T. It's said that using the 26-T trans sprocket will create a long transition period between 3rd and 4th gear.
Note: A 26-T tranny sprocket can only be used with a tin primary. A 26-T will hit the inner aluminum primary on a '65 and later Big Twin.

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Re: gearing

#7

Post by Jack_Hester » Wed Feb 25, 2009 12:40 am

panhead55 wrote:hello everyone. my panhead when in 4th gear feels wrapped out around 55. i am running a motor sprocket at 23, tranny at 25, and rear sprocket at 51. any suggestions on which numbers to run so i can take to the highways more easily? thanks, billy
Billy -

My '59 has had the following, since I bought it in '74: 23T-engine, 22T-tranny, 51T-wheel. My engine/transmission have been tired for as long as I have owned it. But, I took it anywhere in the state (N.Carolina) that I wanted. Never ran it over 45 or 50 mph, except for an occasional hop onto an Interstate to get to the nearest off-ramp. It gave up last August ('08). So, it's under rebuild at the moment. I will leave the 23T-engine compensating sprocket on it, but have installed a 24T-tranny sprocket on the fresh bebuild. After break-in, I will have no qualms about any speed that I want to run. Oil consumption will be higher at Interstate speeds. But, I still don't plan to travel them. Just treat them as a necessary evil to get me to the next 2-lane, if it happens to be in the way of my route.

My reason for staying with this gearing: I can't sight-see at fast speeds; I ride backroads with the least amount of traffic; This gearing is perfect for 55 to 60 mph, with occasional stints at 65 to 70.

Jack

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Re: gearing

#8

Post by Cotten » Wed Feb 25, 2009 2:03 pm

Dale asked:
What RPM do you recommend at a cruising speed of 65mph Cotten?

I have never run a tachometer, so I really do not know .

But my stock 74" had no problem keeping up with a pack running 75 on out-of-state runs with a loaded sidecar rig with 22T on the motor, and 22T on the countersprocket. As I mentioned previously, it still had throttle left.

H-D Big Twins have big flywheels. That huge rotating mass stores energy. The faster they spin, the more energy is safely stored for the next next revolution. The limit is the reciprocating mass that must accellerate and stop and change directions.

Connecting rods are not a weak link, and neither are pistons, if everything else is in order. Similar designs survive in motors that turn twice as fast.
The long valve train with poor angles limits top RPM to much less than other designs, but the powerband still reaches far beyond what the average rider feels is comfortable.

The problem is that motors don't want to be lugged any more than they like being red-lined.

The irony of the last few decades of custom builders is that they gravitated to light flywheels that reach rpm quicker, but lost mass to dampen the forces that want to tear a motor apart. Add the taste for overkill oilpumps that flood everything at high Rs, and big throated carbs with peaky cams that don't even turn on until WFO,...
Many motors were built for high-end performance when riders actually want low-end performance, and detune them with tall sprockets so they virtually idle down the road!

And sadly, many of those motors were balanced with a high factor, and it may well be the balancing that contributes to riders feeling "wrapped out", because they aren't going fast enough!

.....Cotten

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Re: gearing

#9

Post by 51Hog » Wed Feb 25, 2009 6:17 pm

Thanks for the response Cotten.
According to Jack Hester's calculator,

Sprockets 22-37-22-51, Your engine speed at 75 mph was 3750 rpm.

11mm Belt and sprockets, 31-47-24-51 My engine speed at 75 mph is 3100.
That being said, I cruise at 60 - 65 mph at an rpm range of 2400-2700.
after that, vibrations start to fatigue things like the elements in the bulbs, chain guard tabs, primary tin tabs, and license plate....Which is the reason for my current tear down. Hopefully I can find the problem without having to split the engine to check for true on the crank assy.
Dale

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Re: gearing

#10

Post by Cotten » Thu Feb 26, 2009 2:55 pm

Dale figured: "Sprockets 22-37-22-51, Your engine speed at 75 mph was 3750 rpm."

Geez.
Even I thought the motor was turning faster.

....Cotten

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Re: gearing

#11

Post by Frankenstein » Thu Feb 26, 2009 3:04 pm

Here's a rule of thumb for engine speeds: with a final ratio of 3.7:1, engine speed is 3000 rpm at 60 mph. works for most rear tires, pretty much. Even in cars. Just do the math to figure your final ratio, and then do that proportional thing you slept through in 8th grade math to figure for your final ratio. :-)
DD

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Re: gearing

#12

Post by mbskeam » Fri Feb 27, 2009 3:00 am

my bike has a 8mm belt drive and 25T tranny 51 rear

well I finally put this on and was able to get a accurate pace.
so at 60mph I turn over 2600rpm and at 70mph it turns over at 3050

yea I am a bit slow at get it put on .....LOL

viewtopic.php?f=5&t=3184&p=12114#p12114

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Re: gearing

#13

Post by 58flh » Sun Apr 08, 2012 12:04 pm

Cotten wrote:Dale asked:
What RPM do you recommend at a cruising speed of 65mph Cotten?

I have never run a tachometer, so I really do not know .

But my stock 74" had no problem keeping up with a pack running 75 on out-of-state runs with a loaded sidecar rig with 22T on the motor, and 22T on the countersprocket. As I mentioned previously, it still had throttle left.

H-D Big Twins have big flywheels. That huge rotating mass stores energy. The faster they spin, the more energy is safely stored for the next next revolution. The limit is the reciprocating mass that must accellerate and stop and change directions.

Connecting rods are not a weak link, and neither are pistons, if everything else is in order. Similar designs survive in motors that turn twice as fast.
The long valve train with poor angles limits top RPM to much less than other designs, but the powerband still reaches far beyond what the average rider feels is comfortable.

The problem is that motors don't want to be lugged any more than they like being red-lined.

The irony of the last few decades of custom builders is that they gravitated to light flywheels that reach rpm quicker, but lost mass to dampen the forces that want to tear a motor apart. Add the taste for overkill oilpumps that flood everything at high Rs, and big throated carbs with peaky cams that don't even turn on until WFO,...
Many motors were built for high-end performance when riders actually want low-end performance, and detune them with tall sprockets so they virtually idle down the road!

And sadly, many of those motors were balanced with a high factor, and it may well be the balancing that contributes to riders feeling "wrapped out", because they aren't going fast enough!

.....Cotten
(Now thats the truth on todays builds concerning motors!-Well said COTTON!.---richie

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