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Collection, Preservation and Display of Old Lawn Mowers

Ransomes Minor mk7 18 chain tension

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Had a little issue where wooden rollers met blades and threw the chain. I shouldn't have been running her so fast around the garden. :(

I have opened the crank cover and the main chain that drives the blades and rear drum off the release clutch had fallen off.

Clutch cog was a little wobbly but still engaging fine and there is plenty of meat on the friction blocks.  I can't see any form of tensioner there, the cogs are all OK and the chain is in one piece.

It looks about one link loose at hte chain.  I've put it back on but the tension is just not there anymore?  Is there something eccentric in these mowers that allow you to put tension back on the chain?

The chain is constantly throwing after two strips of traction mowing...

Forums

wristpin Sat, 24/05/2014

May be able to help if you post an image. My machine is right at the back of the shed but I think that there may be a large hex nut in the centre of the large sprocket and slackening it allows the sprocket to be moved to tension the chain !

The snatch caused when the cutting cylinder jammed may have shifted it. When you think that you have the correct adjustment rotate everything several times to ensure that a bent shaft is not causing slack/tight spots. If it is, adjustment will have to be a compromise until the run out is corrected.

timsp8 Sun, 25/05/2014

Thank you for the advice!  By the large sprocket do you mean the one that is the drive clutch? Here is my mower with sagging chain removed.

I have just spent 5 hours with it today and cleaned it all right out greased it up and notice that some tension comes onto the chain when you screw in the cutting cylinder height so the blades are meeting.  But the chain sags as much that it touches the big cog between drive and cutting cylinder cog.

I actually tried loosing one link out of the chain and the chain went on OK. But as soon as I put the cylinder back down to meet the shaver it went under way too much tension which would not be good for the bearings.

Do you think it might be a good idea to get another 66 link chain for it? Any ideas as to where to source one? I appreciate that chains do stretch...

hortimech Sun, 25/05/2014

Hi, if you look at the clutch, specifically the center, you will see two holes opposite each other, if you now turn the clutch slowly these two holes will line up with two other holes in the retaining nut behind the big outer plate. If you put two dowels into these holes and then a bar between them, you will be able to slacken the retaining nut and then move the entire clutch up and down to adjust the chain. If you don't understand what I am getting at, remove the three nuts (the ones with the springs under them) that retain the outer clutch plate, remove this plate and you should then see the retaining nut that I am referring to, there is a special tool to undo the nut and if required I could find mine and measure it for you.

 

timsp8 Sun, 25/05/2014

Hi,

Excellent, I have found the two holes and got a pair of strong needle nose pliers in and a monkey wrench. Thunk, it all moves and I can place tension on the chain now orientating the big cog (clutch) off to the right. Repair complete - thanks for both of your advice - greatly appreciated.

She's had a good clean, oil and grease today anyhow in my explorations. I managed to drop the whole left side of the cutting reel out with the shaver blade and blew out all the rubbish with my compressor. Cleaned the thrower plate etc.

One last question :

If I wanted my local agricultural shop to sharpen and set. How do you get the cog in the bottom left through the tin side? Is there a way to remove the cog on the end of the cutter?

I see a small bolt at each end of the cylinder, but I assume that these hold the bearings in place..

 

Cheers

Tim

hortimech Mon, 26/05/2014

The sprocket is screwed on (lefthand thread) , you need a chain wrench to turn the sprocket whilst jamming the cylinder with a piece of wood. Once the sprocket is removed along with the delivery plate, you then need to remove the two bolts at each side and the complete cutter assembly will then drop out

As for your local 'Agricultural shop' being able to regrind your cylinder and bottom block assembly, ask them if they can do loose cylinder grinding, if they do not understand this, go somewhere else, preferably a 'Horticultural shop' or lawnmower repairer.

 

timsp8 Mon, 26/05/2014

Thanks again for imparting your knowledge. I found the mk6 manual here albeit mines a mk 7 your explanation is ten times better and I have a chain wrench in my toolkit. What is a loose grind?

I was planning to send the unit to Lister Wilder. Not sure who else in Oxfordshire to visit. I think there is an Oases Bros in Hungerford.

topgunhorse Mon, 26/05/2014

Do shop around for prices for a regrind.

Locally, I was quoted £60 +vat, £35 +vat and eventually got it done for £25 cash, on an 18" Certes (10 blades on the cylinder)

hortimech Mon, 26/05/2014

Loose cylinder grinding is where you remove the cutting cylinder and bottom block from the machine and grind these separately then rebuild the machine, as against insitu grinding where you remove just the bottom blade from the bottom block, regrind the cylinder whilst it is still in the machine, then remove the bottom block, refit the bottom blade (or fit a new one) and grind this, refit the bottom block. This isn't really possible with your Ransomes without a lot of faffying about, you could do the first part, but would still have to remove the entire cutter unit to get the block out, this sort of negates the benefits of insitu grinding.

You should be ok with Lister Wilders, they are also 'Horticultural dealers'.

 

Mowtown Thu, 05/01/2017

I notice that there are several other comments about the chain tension under another topic which digressed onto this subject. See  Ransomes Marquis Sloper engined...Hand clutch