Drive belt tensioning

[vogli 86]

I've got a 1973 Raider 12, and I've replaced the drive belt, with a 7473 belt (as per  the IPL). It is far too tight, it seems. The metal piece over top of the tensioning pully rides the top of the belt constantly, and because of the angle, never really allows the belt to detension. As a result, it's constantly driving the transmission - I can't stop it. A 7478 belt is too loose, and even with the tension pulley back as far as it can go, there is insufficient tension to keep the belt from slipping. I've tried it with and without the shield in place (it appears that is supposed to help pinch the belt, when the clutch is depressed).

 

It seems obvious to me that I must be doing/missing something stupid/obvious, but I can't quite determine what it is. Any advice?

 

 

Edited June 18, 2021 by vogli
clarification

[ebinmaine 68,313]

Have you double checked the stamping number on the new belt? Being blue that isn't a Toro belt.

Looks like Stens or maybe TSC?

 

Best bet would be to bring the old belt and that incorrect new belt back to where you bought it and maybe the pictures above. Have them measure it in a belt gauge. 

[daveoman1966 3,760]

The blue belt you show is NOT and OEM belt.  The geometry of it is NOT the same as OEM design either....especially with these older babies.  The blue belt is either too wide, too thick, or just unable to drop into the V pulleys and precisely MATCH to shape of the pulley.  Accordingly, the blue belt rides higher in the pulleys...effectively causing a 'shorter' belt. Go get a OEM 7473 belt here...your problems will go ghost on you.  https://www.psep1.biz/arinet.asp?aribrand=TO#

   

[oliver2-44 9,850]

Do a quick compare of the width of the top of the old and new belt and I from the pictures it looks like what Dave said is spot on.  

[squonk 41,321]

I use those blue belts all the time. No issues at all. Just put an 82" on a Raider 14. Works perfectly. Back out that bolt on the idler and move that guide off the pulley some. How about a pic with the pedal depressed.

Edited June 18, 2021 by squonk

[vogli 86]

Yeah, I was trying to do that originally. I loosened the bolt on the idler pulley, but couldn't move the guide. I even tried banging it a bit with a hammer. I've not taken the pulley off completely, but from what I can see, and poking it with a screwdriver, the guide appears to be welded to the arm, or bonded with something.

[pfrederi 17,866]

The arms on tractors of that vintage are welded...non adjustable.

[vogli 86]

 

2 hours ago, daveoman1966 said:

The blue belt you show is NOT and OEM belt.  The geometry of it is NOT the same as OEM design either....especially with these older babies.  The blue belt is either too wide, too thick, or just unable to drop into the V pulleys and precisely MATCH to shape of the pulley.  Accordingly, the blue belt rides higher in the pulleys...effectively causing a 'shorter' belt. Go get a OEM 7473 belt here...your problems will go ghost on you.  https://www.psep1.biz/arinet.asp?aribrand=TO#

   

 

Yeah, I think you are right :-/

I'll check w/ a caliper when I get home this evening.

[squonk 41,321]

Your old belt is worn. That's why it's thinner. Belts wear down on the sides. People think belts stretch but it's minimal. The belt gets thinner and rides into the pulley deeper giving the illusion of a longer belt. The correct belt is 5/8" X 82" You could try an 83" . If someone swapped the engine before you owned it it could have an engine from a hydro tractor with a bigger pulley. I have had one issue with a blue belt not releasing. "Riding the clutch" for 10 minutes in 3rd gear cured it and it's been fine since. I have had more trouble with OEM belts than the Huskee and Napa Green belts.

Edited June 18, 2021 by squonk

[squonk 41,321]

Another thing to check. Make sure our brake band isn't adjusted too tight. That could prevent the pedal from depressing all the way.

[Lee1977 6,776]

The only thing wrong with the blue belt is it is too short. The last OEM Toro belt i bought for my 312-8 a couple years ago is not the same quality as the old Wheel Horse belts.

Edited June 18, 2021 by Lee1977

[Lee1977 6,776]

48 minutes ago, squonk said:

Another thing to check. Make sure our brake band isn't adjusted too tight. That could prevent the pedal from depressing all the way.

THe 73 should have two pedals and the brake won't affect the clutch.

Edited June 18, 2021 by Lee1977

[squonk 41,321]

33 minutes ago, Lee1977 said:

THe 73 should have two pedals and the brake won't affect the clutch.

73 Raider 10 doesn't. My 73 no-name 12 didn't either.

 

Edited June 18, 2021 by squonk

[vogli 86]

4 hours ago, squonk said:

I use those blue belts all the time. No issues at all. Just put an 82" on a Raider 14. Works perfectly. Back out that bolt on the idler and move that guide off the pulley some. How about a pic with the pedal depressed.

 

Here's with the clutch depressed. Sorry, the angle is a bit different in each, and not sure if I had the clutch in equally.

I'd be fine with the belt rubbing some, if the I could disengage the transmission. As it is, it starts a little harder, and I can't shift into gear. If that guide could move...I think my problem would disappear.

 

Note that I still have the brake fairly loose. Perhaps if I tightened that up, I could use the brake to slow the transmission enough to shift, and eventually the belt will wear enough to make that easier. Previously I could shift with just the clutch, before the brake kicked in.

[squonk 41,321]

Belt looks loose enough. Perhaps getting the brake to grab would resolve it. It would stop the transmission gears from turning. Remember you must come to a stop before shifting. I'm thinking the brake is your whole problem. New belt is certainly the right width. 

[Sparky-(Admin) 21,405]

Is the drive pulley on the motor the correct size? Should be a 4”....if someone swapped it up a size that could be the issue. Have you put the old and new belt together to compare size? 

[vogli 86]

The new belt (7473) is 82", or so it claims (I've not actually measured it). I *did* measure the old belt, but my memory is a bit fuzzy. It was something like 82 1/2" or maybe 83", which I figured was due to some stretching over time + some measurement error. I have a 7478 belt that is 84", and it's floppy on the pulleys, even with the idler pulley as far back as it can go.

 

Not sure about the pulley size on the motor. Not being able to measure it at the moment, I'd guess it's probably 4".

[squonk 41,321]

Remember, belts DON"T STRETCH. They get thinner. If you measure the outer diameter of the belt now, it will be within hundreth's of what it was new.

[vogli 86]

Yeah, this new belt just isn't going to work. I think it was the manufacturer (D&D Power Drive Belts) that stretched....the definition of a 7473 belt. The OD of this new belt is 81.5". That's at least an inch less than the belt I'm trying to replace, and a half inch less than the marking on the belt. The depth is about 7/16", and the the width *is* 5/8", but it's just too tight to be usable.

 

I've ordered replacement PTO and mower deck belts of theirs before and never had issues. I had assumed this would be the same. :-/

 

Anyway, I've ordered what I hope should be the proper belt now.

[squonk 41,321]

Gates (Napa green belts) guarantee their belts to be within thousandth's of their advertised length. You don't normally see an aftermarket belt in a half inch size. Just curious where you got that belt from.

Edited June 19, 2021 by squonk

[vogli 86]

Got it off Ebay, advertised as 82", and a 7473 replacement: https://www.ebay.com/itm/111965654095

 

I measured it 3 times, and got 81.5" each time, so if it's measurement error, I'm awfully consistent. Anyway, yeah, I found it a bit surprising as well.

 

I've previously bought belts for my mower deck from that seller, and manufacturer, which I've been happy with. In that case though, I've got plenty of adjustment, so I maybe didn't notice if belts were a little shorter or longer. Anyway, I've complained to them.

Edited June 19, 2021 by vogli

[squonk 41,321]

If there is a Napa near you I bet you could order from them a 5L820W belt from them and it would work perfectly.

 

Belt Angle: 37 Deg Belt Construction: Wrapped Belt Material: Ethylene (EPDM) Brand: NAPA Cord Material: Aramid Cross Section Designation of Belt: 5L Effective Length: 82.15 in

Edited June 19, 2021 by squonk

[vogli 86]

Excellent! Thanks, that's really helpful.