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Loose rivets
15th Sep 2013, 11:34
I purchased a ten quid Flymow from a boot sale. My mate used three different machines to sharpen the totally rounded blade. The edges were like razors - and turning the correct way - BUT, I don't think it cuts very well. I looked to lower, with supplied shims, this blade but intuitively noticed the cut was the wrong edge. i.e., the grass would be pressed down by the slope of the cutting edge.

Now, is it a case of there not being a need for such care due to the velocity, or would pulling on the grass by the cut-angle make a lot of difference?

vulcanised
15th Sep 2013, 11:48
Blade upside down? http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/cool.gif

G-CPTN
15th Sep 2013, 11:50
As long as the sharp edge is the leading edge when rotating the effect should be OK.

ShyTorque
15th Sep 2013, 13:39
My old rotary bladed mower always had a problem picking up damp cuttings efficiently, same problem I think.

I transformed the performance of it by making and fitting two extra steel blades with a "puller" angle of attack. I made these from steel strip, curving them to an aerofoil shape. I then tempered the leading edges and ground them to a cutting edge (also balanced them to keep the whole rotating assembly running true).

lomapaseo
15th Sep 2013, 15:15
Too much iron in the fertiliser

superq7
15th Sep 2013, 15:30
In my experience there is no need to sharpen the blades on a rotary type mower and by this I mean a petrol type, just change the blades when they get damaged by stones fod etc or when out of balance.

I used to have a lawn mowing round about 80 smallish jobs done once a fortnight very lucrative at 10 to 20 a pop.

dazdaz1
15th Sep 2013, 15:38
Wrong type of grass.

D

Checkboard
15th Sep 2013, 16:30
BBC - Learning Zone Class Clips - How does a hover lawnmower work? - Engineering Video (http://www.bbc.co.uk/learningzone/clips/how-does-a-hover-lawnmower-work/6621.html)

Loose rivets
15th Sep 2013, 20:20
the blade on the machine is in 'pull' mode, however, when he's holding one, the blade's leading edge is away from the curve of the tips. Mine are not curved thusly. :hmm:

So, still no definitive answers, though a hint or two that the cutting angle should pull.

fenland787
15th Sep 2013, 22:02
These work fine, got 'em from ebay. They last very well even when reducing half-bricks to rubble. It's an Aussie 'Rover' machine had it for donkeys years still going strong.

Tried to show the curves and cutting angle:

http://i1096.photobucket.com/albums/g325/adriannicol/CIMG1546_zps33b580a4.jpg

ShyTorque
15th Sep 2013, 22:09
Mine's also a Rover Scott Bonnar machine. I made a pair of similar blades to that one.

Maybe it didn't work too well because it was in the wrong hemisphere.... :p