Ransomes motor triple cutter drive clutch

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  • #39891
    boycey
    Participant

    Hi all.
    my clutch was slipping and making a metallic grinding noise so I stripped it down and found that the clutch plates were very thin and the friction plates had worn and had a lip, so the thin clutch plates were sitting inside this lip and there was my metal-on-metal problem!
    So I carefully sanded out the lips so I had flat plates again and whilst at it had the clutch plates re-lined.
    On reassembly I have encountered a big hurdle…
    There is nowhere near enough space on the splined shaft to accommodate all the plates, in fact I can only get 5 of the original on before the splined shaft is “full”.
    Pics below . First 2 pics show the splined shaft with all 10 friction plates on. The remaining splined shaft is 11.44mm.
    Pic 3 shows the metal carriers for the clutch material as being 1mm thick, WITHOUT any clutch plate. There are 11 of these so this will completely fill the remaining 11m of splined shaft, leaving no room at all for clutch material!

    Each clutch plate is now 3mm thick (pic 4)so I am over by 22mm.. ie 42 mm of parts to fit on a 20mm splined shaft, it doesn’t make sense??

    Any help greatly appreciated!

    • This topic was modified 1 year, 5 months ago by boycey.
    #39898
    charlie
    Keymaster

    No photos?

    #39899
    boycey
    Participant

    Trying again!

    Attachments:
    #39904
    trusty220
    Keymaster

    My recollection of those friction plates is that the friction material was not 1mm thick so it sounds like you’ve got too much on there.

    It may help to buy some new if you can get them. Part numbers are MBA2790 for the friction plate with the lining on (and the book says that you need 11 for a set), and the intermediate plates are MBA2791. They are called “Counter Face Plate” and a set is made up of ten plates which do not have friction material on them.

    The friction plates have four ears on the periphery which used to burr over in use so one of the service points was to file the burrs off to make them flat again. The cage that they used to fit into used to have four cut-outs that corresponded to the ears; the ears of the plates used to wear grooves on the drive sides of the cut-outs, so another service point was to file the grooves flat so the the plates didn’t sit in them when the clutch was disengaged.

    The best place to start looking for spare parts would be Ernest Doe Ltd.
    Good luck!

    #39905
    boycey
    Participant

    That’s a great help, thank you. I noticed the burring of the ears and filed those clean, but will need to check the cage next time I’m up there. It sounds to me as if I have relined some perfectly serviceable clutch plates in error! i have searched high and low for replacement plates but they are just not available anywhere. Ransomes stopped making them years ago. There was probably no demand as it seems the clutch plates themselves didn’t wear out!
    I’m now wondering if I can remove some friction material from the 22 sides to get them down to size? Probably a long job and difficult to keep them perfectly flat….

    #39906
    boycey
    Participant

    I’ve just remeasured more accurately and there is still a nagging question…
    Withe the 10 intermediate plates slipped on the shaft, there remains 12mmm of spline shaft exposed. The friction plate metal is 0.95mm each
    .95×11=10.45
    12-10.45 = 1.55mm
    1.55/22 (for the 22 friction pads) =0.07mm and this would have to be the maximum thickness of each friction pad for all 21 parts to fit on the shaft. This cannot be correct surely? This is less than 3 thou!!
    There is no way change the assembly , it’s pretty simple (see attached drawing). Part numbers 9, 14 and 15 all have to fit on p/n 8
    Any thoughts?

    • This reply was modified 1 year, 5 months ago by boycey.
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    #39909
    trusty220
    Keymaster

    I never did measure the total thickness of a new plate but I know the friction material was only a thin layer, no more than 10 thou at the very outside. A shame there never was a workshop manual printed for these machines!

    Some years ago when Ransomes sold off all of their redundant Motor Triple spares it was Bartrum Mowers who bought them all. Bartrums have now been bought out by Ernest Doe Ltd (or so I’ve been told), so it may be worth trying them.

    #39910
    wristpin
    Participant

    So I carefully sanded out the lips so I had flat plates again and whilst at it had the clutch plates re-lined.

    No experience of the the MT cutter drive but assuming correct assembly, the answer must lie in the re-lining. Presumably the firm entrusted with that operation were either given a specification to work to or purported to know the specification?
    The starting point needs to be the correct specification of the friction plates; a ten thou thickness of friction material does seem a bit thin but spread over 11 plates may have been adequate
    Hopefully Doe can help, even just one plate that can be measured may supply the answer. A complete set of plates will be “ gold dust” but I dread to guess the price.

    #39911
    trusty220
    Keymaster

    It may even pay to buy another donor Motor Triple to provide a source of spares for the future. These machines used a lot of spare parts when they were in current use and common sense would suggest that the supply of spares is going to get less as time goes on.

    My experience of the Motor Triple cutter clutch was that the friction material that was bonded to the drive plate was extremely thin but I’ve never seen any worn out. Once the clutch is engaged it wouldn’t slip- all three cutting units had a V-belt at some point in their drivelines and these would be the first to start slipping if the load on the cylinders was excessive, so the clutch was protected. Besides trimming burrs off and filing grooves out of the cage that was all that was needed.

    Good luck with your search for parts.

    #39912
    boycey
    Participant

    Many thanks for this. I believe I have ruined a perfectly good set of plates!
    However the problem was definitely in the clutch. You could hear a metallic gratingf noise `nd the drive pulley to the V belt would stop turning. I am guessing it was a combination of the birrs and the wear to the metal counter-plates that was causing it, and simply cleaning those up would have done the trick!
    I have managed to find a set of used plates on ebay but they are in pretty poor condition. Probably worth a try though.
    And yes i will keep my eye out for a donor machine!
    Thanks all for all your input, much appreciated. I wish I had asked the question before starting the job!

    #39913
    trusty220
    Keymaster

    Keep in touch and let us know how you get on.

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