fixed blade bending?

[woolyhead 15]

I filed the rotary blades in my  Qualcast cylinder style grass mower until they just scraped past the fixed blade and were able to cut a single sheet of newspaper as good as a new pair of sharp scissors, right across the cylinder width. Everything looked perfect but when I put the mower on my grass the rotary blades fouled the fixed one. I found that this was due to the fixed blade bending up slightly when the grass pushed up on it. There is no front roller across the mower on this model. But the mower has two front wheels and these should have prevented the fixed blade pressing down on the grass too much but these wheels are only about 30 mm wide and they don't do the job very well. My main concern is that the fixed blade shouldn't bend under the fairly small upward force imposed by the grass. This is poor design. If I widen the wheels to reduce their tendency to sink into the grass the mower will not work as close to edges as it does now.  Has anyone got any idea how to fix this?

[Top Cats Hat 10]

22 minutes ago, woolyhead said:

Has anyone got any idea how to fix this?

Short of a redesign, I would suggest slightly readjusting the gap between the rotating and fixed blades to find a balance between a good cut and the fixed blade bending but not fouling the rotating blade.

 

I'm surprised that the fixed blade is flexing on a Qualcast mower.  

[Janus 28]

The rotating blade is obviously very close to the fixed blade from what you describe. I acknowledge that you have honed the edge of the blades to get them so close. I am guessing that the method of adjusting rotating blade involves some sort of locking method, be it a nut/bolt or whatever?

 

Although the rotating blades turned freely when manually turned, could it be that when powered at speed that they were able to move slightly towards the fixed blade?  If there is a locking mechanism as above, can this be tightened? 

 

If not, backing off the rotating blade slightly may be the only option.

 

Edited April 4, 2019 by Janus

[woolyhead 15]

Thanks guys. Good ideas both.  I was wondering if there was some way to stiffen the blade?

Edited April 9, 2019 by woolyhead

[woolyhead 15]

I got in touch with a supplier of my sort of bottom blades and he told me that the model of my mower was not intended for long grass. So that looks like it could be true and if so that's how  the bottom blade can bend in long grass. The mower is a Qualcast Concorde model E30. The only way I can think of for stiffening the blade is to remake it in gauge plate and harden it to suit. Any comments?

[Top Cats Hat 10]

2 hours ago, woolyhead said:

I got in touch with a supplier of my sort of bottom blades and he told me that the model of my mower was not intended for long grass. So that looks like it could be true and if so that's how  the bottom blade can bend in long grass. The mower is a Qualcast Concorde model E30. The only way I can think of for stiffening the blade is to remake it in gauge plate and harden it to suit. Any comments?

My apologies, I didn't realise that it was a powered motor. I thought that it was a push mower and couldn't see where the weight was coming from to bend the fixed blade.

[RiffRaff 10]

On 04/04/2019 at 15:23, Janus said:

The rotating blade is obviously very close to the fixed blade from what you describe. I acknowledge that you have honed the edge of the blades to get them so close. I am guessing that the method of adjusting rotating blade involves some sort of locking method, be it a nut/bolt or whatever?

 

Although the rotating blades turned freely when manually turned, could it be that when powered at speed that they were able to move slightly towards the fixed blade?  If there is a locking mechanism as above, can this be tightened? 

 

If not, backing off the rotating blade slightly may be the only option.

 

Have a word with Alex at Dronfield Lawnmowers - he's messed around with mowers for 20 years plus, so I dare say he's come across the problem before.

Busy time of year, don't forget, so he might ask you to drop it in to have a look. Can't hurt to ask!