OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Victa Lawn Mower Frames Disk and blade tightening torques

I have a 19" Victa Corvette on which I removed the disk to give the chassis a thorough clean. I got the blade off without too much trouble.

The mower has embossed on it that the nut holding the disk should be torqued to 60Nm. This seems to be extremely high, and I was not able to get close to it as I could not hold the shaft and disk at that torque.

Questions:
1. Is the 60Nm really necessary?
2. How does one hold the shaft or disk to prevent the shaft rotating while trying to torque the nut?

When replacing the blades, the instructions say to torque the nuts to 14-19Nm. My understanding is that the blades should be a snug fit, but movable by moderate hand pressure so that they can swing out of the way if a hard object is struck. Long before reaching 14 Nm the blades become impossible to move by hand.

I am confident that I have assembled the blades correctly.

Should the blade nuts be torqued to 14Nm even though that will render them totally rigid to all intents and purposes or should one simply use the ability to move them by hand as the guide for correct torque on the nuts?

Thanks
Ken

1) to be honest, I have never used a torque wrench for this, always just did it by feel, taking the centre bolt to a pressure that felt right to me, about 3/4 what i would a wheel bolt on my car.

2) i use cotton based rope in the cylinder, supported by a bar in the hole on the side of a powertorque boss.

Often they wont move by hand, thats ok, they will give if they need to.

Thanks for the response.


That's what I ended up doing.



I tried the rope in the cylinder trick to no avail. Maybe I didn't use enough rope. The boss on my mower does not have a hole - at least, I cannot find one.



Are you saying that you do use a torque wrench for the blade nuts?

Thanks
Ken

Firstly, the rope, it does end up being quite a lot, move the piston to the very bottom of it's stroke, and fill from the top, you can also twist it slowly as you do, to try and coil it in the cylinder, preventing it jamming in the ports.

And as for the blades, no, i do not, sorry for the confusion, I do however find that often when I have applied what I feel to be decent pressure for the job, the blades indeed will not move by hand, and when you consider other methods of engine protection use sheer pins, you can see the blades dont need all that much freedom.

Thanks, Ty.

I also sent the questions to Victa, out of interest to see if they would respond and what their response might be. Here is what they (eventually) wrote back this morning:


Good morning, to answer some of your questions:
a. The blade disc should never be removed from the mower unless by an authorised service centre.
b. The disc should not have to be removed to clean the under side of the mower.
c. Yes if that is the torque on the specification by Victa that is what is required.
d. Please take your mower to a service centre and have them torque up the disc for you as it is not safe to use if not tighten to the correct specifications.
e. The blades should be torqued to 14-19 Nm. The blades will move if fitted correctly not by hand but when there is am impact to them so the blades do not fail or the shaft damaged.


Their response seems to have a bit of CYA ring to it. I suppose that if they said anything else they might fear exposing themselves legally.

I decided to have another search for the hole in the boss. I took the disk off again and did a thorough inspection. I thought the hole might have filled with debris and become 'disguised' under the film of grime that has built up on the boss. Despite cleaning the boss thoroughly and inspecting it very carefully, I was not able to locate a hole. The mower is a Corvette 400 series, that I guess is about 10 years old, maybe older.


Judicious application of a large pipe wrench through the catcher opening allowed me to stabilise the shaft while torquing the nut. Worked beautifully!

Given the absence of a hole in the boss, I wonder how the 'authorised service centre' would have stabilised the shaft to achieve the specified torque. Perhaps they would have relied on the 'rope in the cylinder' method.


Ken

I think most authorised service centres torque by "Rattle Gun" method, either battery or air powered. As Ty said, 3/4 of how tight a wheel nut should be, the typical wheel nut torque is approx 95NM, so it's very close. By the way, is the corvette a 4 stroke briggs?

It's a 2-stroke PowerTorque, VSX160

Ken