Register free!

The Green Industry's Resource Center


Reply
 
Thread Tools   Display Modes
  #1  
Old 07-25-2015, 10:09 PM
roody2333 roody2333 is offline
LawnSite Member
 
Join Date: Sep 2014
Location: lumberton nj
Posts: 160
variable speed belt adjust on 36" walk behind? tight belt = slow?

The variable speed on an older 36" bobcat I have doesn't work. The belt is there, everything looks good (before I broke something).

The sticker on the speed control lever tells me to move the handle forward to "go faster", this actually loosens up on the drive belt with the movable pulley. The more you tighten the pulley against the drive belt, the slower it rolls. Which is confusing because you would think if the adjustable pulley isn't pressed hard against the drive belt, then the belt would be loose and this not transfer much power from the crankshaft - this is the opposite of how probably every single small home owner type propelled mower is. With a small push mower, the only way to make it propel is to tighten up the drive belt when you engage the lever.


There's a threaded rod that goes from the speed control lever to the adjustable pulley. The manual says to take the cotter pin out and tighten the swivel adapter on the threaded rod and then reinstall with the cotter pin and keep making adjustments until it works. Well, I confirmed slightly to be true what I am questioning in the above by tightening the swivel. In other words, the tighter I make the pulley press on the drive belt, the slower it moves. In other words, it Seems like too much stress on the belt to drive it slow as if they assume everyone's going to mow at full speed which is not practical.

Just asking to confirm this before I destroy the belt by making it super tight to move slowly. I adjusted the swivel maybe 3 turns and got it to propel a bit slower but not nearly enough and I can feel how much pressure I have to put on the speed control lever feels like too much. So I went to adjust the swivel more to make it slower and the threads were really stuck bad even soaked with liquid wrench and I actually snapped the rod apart trying to tighten it and now I have to order a new rod possibly (only snapped the tip off and needed the swivel much further up the threads so maybe I can just order the $4 swivel or extract the broken threaded rod in the one I have and use the existing rod).

sorry if to long, just wanted to make sure. Tight drive belt= slower propel? thanks
Reply With Quote
  #2  
Old 07-26-2015, 08:26 AM
AVS Lawns AVS Lawns is online now
LawnSite Senior Member
 
Join Date: Apr 2015
Posts: 965
Yes.

Think snowmobile transmission. The belt gets tight and expands the pulley sheaves. Making the pulley "smaller". Reduce tension , the pulley contracts, making the pulley "bigger".

Slow is tight belt, fast is loose belt.

To adjust start motor and crank lever to slow. Shut off motor. Reach under and make sure pulley is expanded by pulling bottom part down to ground as far as it can. Then adjust tension to keep that pulley split apart.

Also spray some pbblaster on the spring part of the pulley. It's probably frozen at one speed because most people don't move the speed lever much.
Posted via Mobile Device
Reply With Quote
  #3  
Old 07-26-2015, 02:47 PM
roody2333 roody2333 is offline
LawnSite Member
 
Join Date: Sep 2014
Location: lumberton nj
Posts: 160
thank you. I had the mower on its side and the pulley moves freely with the lever so I don't think I need any spray or lube.
Reply With Quote
  #4  
Old 07-26-2015, 03:02 PM
AVS Lawns AVS Lawns is online now
LawnSite Senior Member
 
Join Date: Apr 2015
Posts: 965
Quote:
Originally Posted by roody2333 View Post
thank you. I had the mower on its side and the pulley moves freely with the lever so I don't think I need any spray or lube.
A drop or two on the bolt end inside the spring of 90w won't hurt.

That pulley and the transmission are the only 2 Spendy parts on your mower. Take care of them. The pulley starts at 150 and the trans is upwards of 300 if you can find one.
Posted via Mobile Device
Reply With Quote
  #5  
Old 07-26-2015, 10:18 PM
roody2333 roody2333 is offline
LawnSite Member
 
Join Date: Sep 2014
Location: lumberton nj
Posts: 160
true on those prices being like half of the mower cost. I will keep it lubed, maybe a dab of grease?

I still don't understand why they would make the belt tight like this. At default, at the loosest setting, it is tight so that the trans gets full power from the crankshaft. And then to make it slower you have to actually put so much pressure on the belt that it slows it down. how does making it so tight to go slow not also affect the power the crankshaft is feeding to the blade engage belt since both the blade belt and drive belt are on the main crankshaft?
Reply With Quote
  #6  
Old 07-26-2015, 10:24 PM
AVS Lawns AVS Lawns is online now
LawnSite Senior Member
 
Join Date: Apr 2015
Posts: 965
The belt makes the pulley get larger and smaller. Big pulley=fast. Small pulley=slow. Pulling on the belt to make the mower slower splits the pulley, making the diameter smaller. Release tension and the pulley increases diameter

Fire up the mower and look under it with the speed lever in slow, look at where the belt rides in the pulley. Then move speed lever to fast and look at the pulley again.

It should become clear very quick.
Posted via Mobile Device
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Layout Style:





Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Copyright ©1998 - 2012, LawnSite.com™ - Moose River Media
All times are GMT -4. The time now is 02:21 AM.

Page generated in 0.06562 seconds with 10 queries