42" rear discharge deck breaking springs

[Esbrian 16]

My recently acquired 312-8 with a 42" rd deck is now breaking tensioning springs every time i mow.  The first 2 were old and rusty, the third was brand new but was attributed to mowing through too much heavy debris with worn out plastic washers on the tension bar.  Having replaced the plastic washers, spacers, spring, and mowing in normal lawn conditions, the most recent failure tells me something else is probably going on.  It could be incorrect parts, incorrect assembly, or something else i havent considered...

 

I'm currently using toro 100071 springs.  The deck is not in great shape so the spindles could have some wobble due to sheet metal fatigue.  It mows beautifully until the spring fails.  Any thoughts on what could be wrong here?

[8ntruck 7,004]

Where is the spring breaking?  That could be a clue to what is causing the spring to fail.  

 

Working from memory, one end of the spring connects to a bolt on the deck, and the other end hooks into a hole in the tensioner bar. 

 

Assuming the hooks on the end of the spring are breaking, it might be due to sharp edges on the connection points.  They could create a notch in the spring, which could lead to a fatigue failure at the notch - especially in a high vibration application on a deck.

 

Good luck.

[Esbrian 16]

3 minutes ago, 8ntruck said:

Where is the spring breaking?  That could be a clue to what is causing the spring to fail.  

 

Working from memory, one end of the spring connects to a bolt on the deck, and the other end hooks into a hole in the tensioner bar. 

 

Assuming the hooks on the end of the spring are breaking, it might be due to sharp edges on the connection points.  They could create a notch in the spring, which could lead to a fatigue failure at the notch - especially in a high vibration application on a deck.

 

Good luck.

The springs are breaking maybe 3.5" from one end or the other.  When it happens i have to search for spring parts and have only found a couple of pieces... bad news for my blades in the future, when i mow over the pieces. I feel like either the springs are too short (wrong part for the application) or they are being torqued too much due to deck action.  I read that the second lock nut on the bolt that the spring loops around must not pinch the end of the spring, but how close is too close? I dont think i am going too tight on that but if i was then the spring would not be able to twist as it extends and this would apply additional stress.

[Ed Kennell 38,174]

I'm puzzled but interested in the answer to this problem.    More eyes on pictures may help.

[8ntruck 7,004]

Are the springs close to the attachment frames on the deck?  Could they be vibrating against the frames?

 

As far as the lock nut tightness goes, I think that the spring should swing freely on the bolt.  Leaving the lock nut 1/32" away from the spring should get you there.

 

Truthfully, I have never messed with the tensoning springs on any of my decks, so everything I am saying is opinion. (bluntly, I'm guessing)  

 

Springs too short?  If the attachment points are factory, and the springs are Toro replacement parts, they should be the correct length.  The question here would be is the belt too short, which would stretch the springs more?  Pulley size would also affect how far the tensioning spring stretches to work.

 

You could go to a hardware store and find some longer springs.  There will be a point where a longer spring won't provide enough tension to drive the blades.  A longer spring with heavier wire might be a possibility as well - heavier wire = stronger spring, longer spring = less stretch.

Edited September 15, 2021 by 8ntruck

[daveoman1966 3,751]

(1) Does the tension bar slide freely on the nulon guides...or does it jam at any point or position?  (2) is the spring rubbing on something (unlikely if breaking at 3" from end). 

42 " Rear disch deck ought to look like this.  NOTE that the tension bar MUST slide free

 

 

Edited September 15, 2021 by daveoman1966

[Esbrian 16]

2 hours ago, daveoman1966 said:

(1) Does the tension bar slide freely on the nulon guides...or does it jam at any point or position?  (2) is the spring rubbing on something (unlikely if breaking at 3" from end). 

42 " Rear disch deck ought to look like this.  NOTE that the tension bar MUST slide free

 

 

That is how the deck belt is routed on mine and the tensioner moves freely back and forth if i squeeze the belt together by hand.  However, the end of the spring that hooks through the hole in the bar i have hooked opposite to your picture, ie the end hooks around the edge of the bar rather than through the hole. Not explaining it well but will post pic tomorrow. That would apply pretty different stresses on the spring i would think

[8ntruck 7,004]

What you are saying is that the spring is not quite parallel with the tensioner?

[daveoman1966 3,751]

1 hour ago, Esbrian said:

That is how the deck belt is routed on mine and the tensioner moves freely back and forth if i squeeze the belt together by hand.  However, the end of the spring that hooks through the hole in the bar i have hooked opposite to your picture, ie the end hooks around the edge of the bar rather than through the hole. Not explaining it well but will post pic tomorrow. That would apply pretty different stresses on the spring i would think

I understand what you are sayin' about hooking the spring end from the OUTSIDE of the end of the tension bar, as opposed to hooking it thru the hole from the INSIDE. I don't know of what consequence that might be, but ALL of my 36, 42, and 48" deck pics show the spring hooked from the INSIDE. (I know...the center pulleyt is on upside-down.)

 

Edited September 15, 2021 by daveoman1966

[peter lena 8,627]

@Esbrian  agree with others on the possibilities  of that  spring tensioner issue , think that the wear and vibration state of this deck is the real issue , with weak  spindles and other spinning / balance points out of sync, that deck is probably in a very high buzzing state .  drop the deck  and verify what is going on ,  anything that is loose wobbly or rough is like a rock in a garbage can . every driven state , should be solid , smooth and easy to function . rebuilt a number of these , its glairing to me . just my own experience , no offence intended , pete

[Lee1977 6,659]

I think it was just a bad batch of springs. I had one to break on a 1985 deck, I think it was just too hard. The hook snapped off at the sharp 90 degree bend. 

The clutch spring also broke on that 312-8.  

Edited September 15, 2021 by Lee1977

[Ed Kennell 38,174]

9 hours ago, daveoman1966 said:

 

 

 

I'm curious Dave.   Is there a reason to have the center pulley unside down?     The two outside blades are rotating quite a bit faster than the center.

[roadapples 6,983]

The hook end of the spring on my SD 42" deck broke off. So I  took the slide bar off and cleaned everything up. Then I used a piece of 10 Guage copper wire and put it through the spring 2 wraps back and made a loop to hook on the bolt until I got a new spring.

   "Don't get ahead of me here"

That was about 15 years ago and it's still like that and working fine...

[JoeM 7,874]

I am kind of with Pete on this one. I would remove the belt and double check the pulleys for true and tightness. 

[Esbrian 16]

9 hours ago, peter lena said:

@Esbrian  agree with others on the possibilities  of that  spring tensioner issue , think that the wear and vibration state of this deck is the real issue , with weak  spindles and other spinning / balance points out of sync, that deck is probably in a very high buzzing state .  drop the deck  and verify what is going on ,  anything that is loose wobbly or rough is like a rock in a garbage can . every driven state , should be solid , smooth and easy to function . rebuilt a number of these , its glairing to me . just my own experience , no offence intended , pete

No offence taken, this deck is junk!  I think it is beyond rebuilding, there are too many thin spots - it would be less welding to scratch build, but im not set up for that nor do i have the skill set.

 

I believe the spindles i have in it are good enough, no play in any of them.  The deck shell around the center spindle is weak though, so it is definitely getting a lot of unwanted vibration.  Im really just trying to get through this mowing season, which is probably only 2 more passes around the yard.  I will try the spring hooked through the hole as per yours and others' photos, understanding that the failure is more likely attributable to the deck's condition.

[Esbrian 16]

8 hours ago, Lee1977 said:

I think it was just a bad batch of springs. I had one to break on a 1985 deck, I think it was just too hard. The hook snapped off at the sharp 90 degree bend. 

The clutch spring also broke on that 312-8.  

Unlikely in my case, there is no way the springs I've lost are from the same batch.  One came on the deck, another pulled from a 70s sd deck (longer spring), and the last two were new but from different vendors and different colors.  It is POSSIBLE that the 3rd failure launched off into the wilderness rather than breaking, as the top lock nut was missing after i noticed my tension was gone.

[daveoman1966 3,751]

6 hours ago, Ed Kennell said:

 

I'm curious Dave.   Is there a reason to have the center pulley unside down?     The two outside blades are rotating quite a bit faster than the center.

This is NOT one of my decks...I downloaded (stole) this pic a while back, just to show the UPSIDE-DOWN Center Pulley.... Since, I've added other notations onto it.    

[Ed Kennell 38,174]

2 minutes ago, daveoman1966 said:

This is NOT one of my decks

I really didn't think it was yours Dave.    I do wonder though....is there any advantage to having the blades turn at slightly different RPMs?

Like the varying tire tread design to curb noise and vibration.

[daveoman1966 3,751]

8 minutes ago, Ed Kennell said:

I really didn't think it was yours Dave.    I do wonder though....is there any advantage to having the blades turn at slightly different RPMs?

Like the varying tire tread design to curb noise and vibration.

Don't know...never tried it.  

[peter lena 8,627]

@Esbrian thanks for the feed back , note your almost at end of cutting season , hope you can find a better deck , that is not rotted  or neglected , that needs a rebuild , not  that difficult to do ,  its the detailing of that build that makes the difference . that thin drive belt center area on yours is the starting point of your problem . made a number of changes to my rebuilds , won't mention here , it bothers too many , hope you make out , good luck , pete 

[Esbrian 16]

14 hours ago, peter lena said:

@Esbrian thanks for the feed back , note your almost at end of cutting season , hope you can find a better deck , that is not rotted  or neglected , that needs a rebuild , not  that difficult to do ,  its the detailing of that build that makes the difference . that thin drive belt center area on yours is the starting point of your problem . made a number of changes to my rebuilds , won't mention here , it bothers too many , hope you make out , good luck , pete 

Pete, point me in the right direction? I have a 42" sd deck that is solid aside from rot at the chute side rear wheel bracket and a crack near the center spindle mounting point.  The rot by the chute is a no brainer, easy enough.  Interested in recommendations for long term fix at the center spindle.  Is it as simple as replacing the center section of the deck top with heavier steel? Happy to start a new thread if appropriate, i realize this is a different topic.

[peter lena 8,627]

@Esbrian , Brian , the pictures of the deck show significant wear and metal loss , while you can replace those areas , that is a lot of work , just to start on the spindle / pulley rebuild. my experience says find a more stable rot free deck , to refit. on a past deal , I  gave the buyer an old deck like yours , he was glad to get it , I  was glad to loose it . only the formed corners of an old deck , unless rotted out , are worth saving . if you are intent on rebuilding that deck , totally strip it out , and refit new steel , overall. then go about spindle rebuilding , etc. my vote is find a better deck with no rot , done a few of those . your decision, pete   

[Ed Kennell 38,174]

31 minutes ago, peter lena said:

my experience says find a more stable rot free deck

Same here Pete.       When I retired 15+ years back and was accustomed to working 60 hours a week, I needed projects to fill my time.   I rebuilt many old decks by totally  lining the inside with 1/16" steel.    I only used hand tools grinders and a mig.   Slitting and bending to form the compound curves and bolting in place for the complete welding.   I know I spent 150 -200 hours to rebuild a deck.   Add in the welding and grinding comsumables and the bearings and paint and $10/hour labor and you have a $2000 deck.  I sold most of them for $300.

 

Point is, unless you are looking for a project, come to the big show and buy a completely rebuilt deck from Mac for $3-500.

 

 

[peter lena 8,627]

@Ed Kennell agree with you on that , once you know what's involved , you know what's going to happen . keep it simple , that's why I  am such a lubrication nut , it just keeps metal alive , pete

[tunahead72 2,412]

1 hour ago, Ed Kennell said:

... Point is, unless you are looking for a project, come to the big show and buy a completely rebuilt deck from Mac for $3-500.

 

Details Ed?  I should know who Mac is at this point, but I don't.  Who is he, and where does he usually set up?