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Collection, Preservation and Display of Old Lawn Mowers

Dennis Z roller disassembly advice...

My first post, so hello All...

I have recently developed an unhealthy interest in old Dennis mowers. I have a couple of Howard Gems and I dont have much work for them so since we have a bit of grass a nice old mower seemed a great idea (to me..) I am in Guildford so a Dennis seemed appropriate. Anyway...

My Type Z is from 1949 and in really great shape but for one issue : the rear roller sections are all stuck. This is not the oil bath type. I have the roller out, bearings off, spacers off. All I have is the roller with bare shafts sticking out each end. I cant persuade the outer sections to come off. Can anyone shed some light please ? Is it only compacted grime locking them on or are there some fixings under the four pressed caps at the roller ends ? Or some other thing ? I am not too keen to knock it apart with greater force than I have. I thought about making a couple of frames to clamp the roller sections and then to jack them apart. If it only grime I will give that a go. I have another type Z in really poor shape so I could practice on that with a bigger hammer.

Any guidance highly appreciated. Thank you. Regards Andrew




wristpin Sat, 18/04/2015

Welcome aboard the forum.

While I have no experience with a Dennis dry roller but have dealt with a frw seized up Ransomes ones. From your description it sounds as though you've got to the stage where they should pull off and that its a mixture of rust, soil and dried out grease that's causing the problem.  With the Ransomes ones I have left the whole assembly soaking in a drum of diesel for a week or two and then used the apparatus in the attached image to get the sections moving.However, to date have only had to tackle a 20" roller!

I'd certainly be very cautious about attacking it with a heavy hammer - old cast can be rather brittle!

AMC46 Sat, 18/04/2015

Thank you for the advice and photos. I will make up a wooden clamp arrangement as you have. The roller is in a tray of diesel tonight. I was a bit stingy with the volume so i will have to rotate it regularly. I have some sponges over the two joints to help. I hope it will free off with some leverage. I didn't want to start hitting it, it would be a shame to damage it because it is not very worn. Unlike the spare which looks as if it has clocked up a good few miles on hard surfaces. Regards Andrew

wristpin Sat, 18/04/2015

Fingers crossed then! As long as the diesel is just over the centre line it should do the trick. I have a 30" Dennis that had a dry roller that was in a bad state but a good engine and a re-bladed cylinder . However I acquired another one as a trade in (was in the mower business) that had not long had a wet roller conversion so I built up a machine from the two so never probed the workings of the dry set-up and the parts books that I have only show the wet set up..

My clamping/turning apparatus is best described as crude but effective! If yours is a three piece roller, with a bit of luck you will be able to grip the centre and then get each outer off in turn. With one of the two piece  Ransomes in my pics I had to fight to get one roller off and was then left with an "immovable" shaft sticking out of the other one, Fortunately the bearing area inside the roller was one continuous casting so I was able to support it with some thick wall tube and press the shaft out under a 50 ton hydraulic press! In actual fact the slow and steady pressure moved the shaft with hardly any movement on the pressure gauge. However I know of someone who tried the same thing on a cast roller with two separate bearing areas and while the lower one was supported under the press the shaft held in the top one enough to break the casting. Fortunately he found someone with the skills to weld weld it.

  Will be interesting to know how you get on. 

AMC46 Fri, 24/04/2015

Thank you for the advice. 

I made a couple of 1.2m wooden 'wrenches' like yours but not so nicely made. Having basted the roller for most of a week i levered away with no real effect. I added some rubber under the clamps to stop slippage and with a a club hammer on the wrenches saw the drum turn. It would only turn a few mm probably the backlash in the locked up through gear shaft. The drum became a bit more loose but only within the 2 or 3mm zone. There are four pressed steel 1" plugs in the roller ends. I knocked two through and put a bearing puller on. With some preload applied and then a lever waggle a gap began to open up on the drum. once there was a bit of a gap only the puller the  was needed. Both sides came off fine and inside was not so bad. There are the remains of felt rings around the drum joints. I can see why the oil bath type was developed. They must have stuck with the dry setup for 25+ years though. Can you get felt strips anywhere do you know ? 

The through shaft and idler gear were fast. The idler stub gear shaft broke at the grease cross hole while undoing it. i had one made at work today. The through shaft appears to have turned the bushes because the oil holes are not open to the shaft. with effort the through shaft was worked back into free movement. It is nearly all back together. One side is very free driving the gears but the other side is too stiff to turn by hand as it goes on. a bit of work to east the big journal fit. maybe the roller bore is a bit oval. The smaller bore side is free.

New chains, new drum bearings. soon be good to go again. Hopefully a pleasure to turn rather than a handful. 

At the end of the year i may strip it and clean it up for painting it nearer the original colour. Looking forward to laying down some Dennis stripes in Guildford...