Drive Pulley Size

[jsasur 0]

Stupid question, but I measured all the drive pulleys for my 42" RD deck and it appears they would take a 5/8" v-belt.  OEM is 1/2". Part# 102741 (for engine drive to middle spindle = 97").  I cut heavy grass and would think that the slightly thicker belt would ride a bit higher in both the drive and deck pulleys, making the belt run a bit faster and creating a little more RPM's at the blade.  I would also think that it would be a bit stronger too.  Would have to get it a bit longer as it would sit higher in the seave.   Anyone running 5/8" belts?  Would there be problems if you did?  Couldn't find anything on this topic in the FOrum.

[Don1977 604]

The way the belt on deck runs on the back side around the idler I don't think a 5/8" belt will be flexible enough.. I suggest you check the Idler slide to see if it slides free.  Could be that it needs a new spring. The most expensive thing it could be is worn out pulleys.

[jsasur 0]

thx for the reply.  I was talking about the main drive belt from the horizontal engine pulley back down to the deck (not the deck/spindle belt).  I miced it out and it can take a 5/8"  vbelt with no problem.  It is a stepped  4"  and 5" pulley.    Anyhow, any reason why I can't use a wider belt?

[shallowwatersailor 3,213]

A V-belt transfers it's load on the sides. Will it still be within the sheave wall?

[jsasur 0]

Well, I took a chance and bought a 5/8" v-belt, although WH recommends a 1/2" belt.  Just added an inch length. It fits and rides perfectly on all pulleys.  Right away, I noticed a faster blade RPM, a better cut and smoother belt operation.  So, why does WH recommend 1/2" rather than 5/8"?  It is a stronger belt and will last longer too!

[953 nut 51,779]

At 1000 RPM an"A" belt (1/2") will transfer about six horse power and a "B" belt (5/8) about 25. As long as the belt is fully seated as you stated it is no problem, just a little over kill. I guess   just used the "A" belt to keep costs down. The "B" may outlast the "A" which could offset the cost, who knows. I would think a new "A" might also have given faster blade RPM, but you may be onto something here. Post a follow up after you have run it for a season and let us know what you think.

 

 

 

Edited July 29, 2013 by 953 nut

[Jeff-C175 7,195]

I wonder if a "B" would ride too high in a NEW pulley? 

 

Perhaps your pulleys are somewhat worn (whose aren't?) and the belt rides lower and works OK.

 

Some belts don't 'like' to be bent over backward on an idler pulley either.

[jsasur 0]

Pulley does not seem to be worn.

At  2000 engine rpm,  the 5†drive pulley with a ½†v-belt  sitting deep into groove,  the belt will travel 40 feet/sec.

At the same engine speed, the 5†drive pulley with a 5/8†v-belt  sitting higher in the groove will travel  44 feet/sec.

This works out to be about a 10% increase in belt speed which translates  to about a 10%  increase in cutting blade speed at the same engine speed using a wider belt. 

Also since there is more sidewall belt to pulley contact with the larger belt, I would think that more power transfer with less slippage.

Negatives.  Cost is about $5.00 more for the larger belt.  Wear due to flexing may increase with a wider belt. 

Still can't figure why WH specs the A belt rather than a B belt