OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Scott Bonnar 45 for rebuild

Hi bonnar_bloke, and a warm welcome to the forum.
It's always great to welcome another Scott Bonnar aficionado on board; especially one that has used SB45's over a 25 years+ time frame.

You have bitten the bullet and posted (for the very first time, and it's great to see you posting) on a thread that creates a lot of debate. There are 2 schools of debate here; those that believe that there should be a slight contact....and those who don't. I am unashamedly, one of the latter. If you care to look at the video that Joe Carrol and I have just done...Click HERE you will see that I set the cylinder reel at minimal clearance and found the cut to be perfect.

Many people put great importance upon cutting paper...these machines are designed to cut grass..there is a lot of difference in the structure of paper to grass.
The method I employ still cuts paper...but not cigarette paper; but there is still a very slight clearance between the cylinder reel and bed-knife.

To achieve this, the cylinder reel bearings have to be in perfect condition and the reel and bedknife sharpened by an engineer (as you have).

What we want to achieve here is not a scissor cutting action, but a scything action... to achieve this a 90 degree flat sharp surface on the bed-knife is essential and the cylinder reel helix perfectly ground to match the bed-knife...with (using my method) minimal clearance.

I have spoken to various greenskeepers, (whom I know personally) who employ both methods, and both swear by their way of doing things.....I guess it's a matter of personal choice...you achieve the results you want to...so do I...So we're both happy little Vegemites!

One of the greenskeepers, that employs the minimal clearance methods, just prepared the greens for the National Lawn Bowls Championships, held late last year.
But as I have stated, there are 2 lines of thought...No one is right or wrong....that is called a conundrum; and I guess that is what this is...no right or wrong answer. Just a matter of choice.
But I will leave you with this to ponder on;

bonnar_bloke ,here is some info, that you might find of interest.This is written by a turf expert that prepares all the championship golf courses in the USA.

Myth: You must have contact between cylinder and bedknife.

Fact: �You do not need contact between the reel and bedknife to cut turf grass. Contact between the reel and bedknife will generate heat which will have many effects on not only the turf grass, but also on the traction unit. The heat generated between the reel and bedknife will tinge the leaf blade. Also that heat can cause the bedknife to expand which will tighten the cutting unit up even more. The tighter the reel - bedknife contact, the more strain this puts on the traction unit which can cause hydraulic hose failure and premature failure of the hydraulic system�.

Contact between cylinder and bedknife causes drag requiring greater effort to turn the reel and in turn this greater effort has an adverse effect on drivelines and engines. This drag also leads to rapid wear and loss of sharp edges, as well as a poor quality of cut. With contact you have the undesirable �scissor� action instead of the desired �scything� action. It is the scissor action which damages the turf plant and can prolong the healing process.

Myth: New bedknives are �true� and don�t require grinding.

Fact: �New bedknives are certainly not true coming from the factory. Every bedknife that gets installed on a bed bar needs to be ground properly in order to achieve a consistent quality of cut. The bedknife is the single most important factor in achieving a great quality of cut. The bedknife�s job is to position the grass before the reel blade cuts it. Depending on where the position is will depend on how clean and consistent your turfs after cut appearance will look.

Bedknives will take the shape of the existing bed bar once tightened. By grinding the bed knife properly it will give you a smooth surface that you will then align to a reel that has been ground to a true cylinder. Once this is complete you will have 2 perfectly aligned surfaces that can achieve the quality of cut that everyone is looking for. It is very important that the bed knife is ground to its proper angle (manufacturer�s recommendations) in order to maintain high quality turf grass.

bonnar_bloke, on your first post, I hope it will not be you're last and most of all, to the OutdoorKing forum.