Pulley ratio

["Manic-Mechanic" 1,323]

I am setting up a 50” side sickle 3600 rpm off the PTO

 

 

Is this correct and will I be running too fast with a 4” drive pulley?

Edited 13 hours ago by "Manic-Mechanic"
calculation correction

[8ntruck 8,151]

Your math looks about right. 

 

What final rpm at the wobble box drive were you looking for?

[gwest_ca-(File Mod) 11,731]

You sure do not want to run them very fast because they will shake themselves apart. I mow at just a bit above idle for that very reason.

["Manic-Mechanic" 1,323]

18 minutes ago, 8ntruck said:

Your math looks about right. 

 

What final rpm at the wobble box drive were you looking for?

Not even sure what is recommended, but used this math to at least try and figure what I end up with and if that is in fact, too fast?

My concern is trying to use the PTO Clutch as a drive.

I could remove the whole affair and put another drive pulley directly on the engine, set up the old pedal latch as it would align.

Edited 14 hours ago by "Manic-Mechanic"

["Manic-Mechanic" 1,323]

7 minutes ago, gwest_ca said:

You sure do not want to run them very fast because they will shake themselves apart. I mow at just a bit above idle for that very reason.

No, definitely do not want that to happen! Especially what all is involved getting one set up and running!

["Manic-Mechanic" 1,323]

21 minutes ago, 8ntruck said:

Your math looks about right. 

 

What final rpm at the wobble box drive were you looking for?

What would you recommend?

["Manic-Mechanic" 1,323]

21 minutes ago, gwest_ca said:

You sure do not want to run them very fast because they will shake themselves apart. I mow at just a bit above idle for that very reason.

Do you run off the PTO Clutch?

[8ntruck 8,151]

Just now, "Manic-Mechanic" said:

What would you recommend?

I never had a sickle mower, so I don't know exactly.  There is a lot of mass shaking back and forth in one of these things, so that makes a lot of forces in the drive system each time the sickle bar changes directions.  The faster you run them, the higher those forces will be.  More force means higher stress in the drive components, which leads to quicker failures.

 

 I'll guess that the owner's manual suggests an operating speed.  You might find a manual in the files section of the forum.  I'd also guess that the longer the sickle bar, the lower the speed.

["Manic-Mechanic" 1,323]

41 minutes ago, 8ntruck said:

I never had a sickle mower, so I don't know exactly.  There is a lot of mass shaking back and forth in one of these things, so that makes a lot of forces in the drive system each time the sickle bar changes directions.  The faster you run them, the higher those forces will be.  More force means higher stress in the drive components, which leads to quicker failures.

 

 I'll guess that the owner's manual suggests an operating speed.  You might find a manual in the files section of the forum.  I'd also guess that the longer the sickle bar, the lower the speed.

Incredulously no, the manual is not very helpful, only a vague reference slowly starting the sickle, increase gradually to full throttle. As the units were originally engineered to the old direct drive pulley, some 2.5 inches, not sure what speed is achieved. I can do the math with 2.5 representing D1 I suppose. As stated earlier, I can mimic the old direct drive set up with a pedal. The PTO Clutch are a strange bird to try and adjust the brake pad and keep it still while not in use, they get extremely hot!

Edited 13 hours ago by "Manic-Mechanic"
added math

["Manic-Mechanic" 1,323]

My final assessment is the change of D1. I can do a 3" easily, reverting back to direct drive with a pedal, or a smaller cone on the PTO Clutch.

All putting the cart before the "horse!"

[Pullstart 68,164]

I’ve shaken one to bits and it was my custom front mount mower.

 

https://www.wheelhorseforum.com/topic/82286-alright-db-front-mount-sickle-bar-on-a-wheel-horse/?page=5&tab=comments#comment-883507

Seven Fifty Me currently has a broken sickle bar itself.  Only about 18” cuts 

 

https://www.wheelhorseforum.com/topic/108858-seven-fifty-me/?tab=comments#comment-1186818

 

Maybe I’m a glutton for punishment!  I do know, I’ve probably used these for a little more than they were designed to cut, and they lasted longer than they should have!  

 

Edited 7 hours ago by Pullstart

[ri702bill 10,025]

It looks like using the later PTO pulley you would be overdriving it speedwise. Can you use a larger driven pulley - bigger than the PTO one - to underdrive it??

["Manic-Mechanic" 1,323]

3 hours ago, ri702bill said:

It looks like using the later PTO pulley you would be overdriving it speedwise. Can you use a larger driven pulley - bigger than the PTO one - to underdrive it??

There’s no room to go bigger on the driven pulley.

squonk had mentioned a variable speed pulley, I'm not too familiar with these, does seem feasible 

Edited 3 hours ago by "Manic-Mechanic"

[cafoose 3,488]

Post #23 is how I solved the speed problem on my sickle and it seems to work at max engine rpm:

 

Other info on my sickle:

 

 

[Racinbob 12,233]

10 hours ago, gwest_ca said:

You sure do not want to run them very fast because they will shake themselves apart. I mow at just a bit above idle for that very reason.

 

Exactly. Just slow the engine down. The first time you fire it up you'll get the feel for where the sickle wants to run. When I do all the paths out back I'll be running it for over 3 hours. Just above idle give me both the proper sickle speed and tractor forward speed in 1st gear. Not only would full rpm shake things apart (both me and the mower) the forward speed would be too fast (3 speed 854). Then I can talk about engine noise as well. 

Edited 4 hours ago by Racinbob

["Manic-Mechanic" 1,323]

30 minutes ago, cafoose said:

Post #23 is how I solved the speed problem on my sickle and it seems to work at max engine rpm:

 

Other info on my sickle:

 

 

I see the larger driven pulley after some mods, how do you keep tension on the belt? 

["Manic-Mechanic" 1,323]

I have a thought, "I know right", what about swapping the pulley housing? switch out the stub shaft and bearings to get the length reduced, and the pulley diameter reduced?

There is a difference in length, curious to find out...

Edited 31 minutes ago by "Manic-Mechanic"