Rebirth of a 6 Foot Flail Mower

[vintageandclassicrepairs]

Hi Andrew,
I am enjoying watching the progress on this project
You neatly skipped the reassembly of the gearbox
Was there much involved in setting up the gear mesh and or preloading the pinion bearings??
I rebuilt a Moto Guzzi bevel box last week,  same idea on a smaller scale

John

[awemawson]

I set the pre-load on the opposing taper rollers on the pinion shaft by feel - no book values to work to so I set it (with that locking nut that I had to make) to give slight resistance to turning. For the wheel pinion mesh there were shims on either side that I had to juggle with, again just by feel - a compromise between zero backlash and smooth operation.

The result is a marginally stiff box,though easy to turn by hand, my argument being it will become looser in use not tighter.

[awemawson]

Time rather short today as the bacon was due to be sliced having finished curing - 60 packs of 6 rashers cut to a generous 6 MM 

However I got on and made up new studs to replace ones damaged on some U-clamps when I had to cut them off with oxy-acetylene  These clamp the 60 mm tubular 3 point linkage to another 60 mm tube that runs the width of the flail. I'd hoped to save the studs by just heating the nuts and apply massive torque, but they started shearing 

So, first prepare 8 off 20mm blanks, chamfer them, thread them M20 x 2.5 - then eventually they will be welded onto the U shaped bit of the original clamp having cut off the studs. That will need some form of jig to keep the spacing accurate.

I used a Coventry Diehead - always a bit tricky on the larger threads as the torque is enormous. The inconsistent length of thread is because the die head was moving my carriage stop before tripping and opening the dies. Doesn't matter as the errors are longer rather than shorter.

[Will_D]

Time rather short today as the bacon was due to be sliced having finished curing - 60 packs of 6 rashers cut to a generous 6 MM

Is this closure on the new pig-stys thread and thier cute little inhabitants? 

Another great build Andrew - you are an inspiration

[awemawson]

Never mind Will, Robert the Boar will be coming to stay shortly and the cycle will start all over again 

[awemawson]

So today was 'remake the U-Bolts'

Firstly I make a crude jig by drilling correctly spaced holes in a scrap of Scaffold Tube. Then checked that the old U-Bolts were a nice slide fit in it before I chopped out the crescent shaped bit that I needed from all four.

Next I cleaned up the old welds and glued them back together, and gave them a coat of zinc rich paint while they were still warm

Three fitted nicely but the fourth needed it's legs squashing slightly to be a comfortable fit.

[awemawson]

So back from a few days away and back to the re-build. What's been giving me sleepless nights is how to get the main flail rotor back into the chassis in a controlled fashion to let me align and bolt up the flange mounted bearings that retain it. The chassis is asymmetric, so when lifted hangs at an odd angle, and the rotor shaft is bally heavy and the flails get in the way of jacks and wedges.

Eventually, by dangling the chassis from a strop on the forklift and jacking up the shaft I was able to get the left hand side (which is a plain 2.5" hole in the chassis) threaded together, and with judicious joggling could lower the chassis so the right hand end (which has a slot to allow the rotor to enter) to go roughly into place.

It was then a case of wiggling and huffing and puffing until the four 16 mm bolts lined up with the retaining baffle / ring threaded holes. Technically trivial, but not easy due to the sheer mass and un-cooperative nature of the parts. In one case I did have to turn a bolt end down to it's minor diameter to give a lead into it's hole, but eventually it all went together and has been torqued up to 'murder tight' 

I'm now rather regretting asking my 'sand blasting tenant' to blast the remaining bits, as he can't do it until Tuesday PM and I could do it myself this after noon - but having asking him it's unfair to not go ahead as agreed.

[awemawson]

When I dismantled the flail, I had huge problems withdrawing the jackshaft drive UJ yoke female spline from the output shaft of the gear box. They were thoroughly jammed together. So I decided that it would be a good idea to dismantle that bit of the UJ letting me remove the yoke. This let me sand blast in my cabinet blaster the female spline to clear out any remains of rust or whatever, and check that I'd achieved the required sliding fit. That spline will be re-assembled using Copper Ease anti scuffing grease.

I also dismantled and cleaned the needle roller bearings (32 rollers per bearing) to check that they'd survived the considerable onslaught they received parting that spline. Pleased to say that they had 

So, the obligatory zinc rich primer and a top coat of black on the yoke, and back together they went.

[awemawson]

I don't intend to dismantle the entire jackshaft - it's bearings are good as are the other six U/J bearings, and I suspect puling it apart will cause more problems than it solves. It's in a position that if it needs attention in the future no major dismantling is needed to get at it - so leave well alone 

I just gave it a bit of a clean up - coagulated grease baked hard after a few decades - and it'll go back as it now is.

[NormanV]

Time rather short today as the bacon was due to be sliced having finished curing - 60 packs of 6 rashers cut to a generous 6 MM

I hope that you washed your hands after cutting the bacon. You wouldn't want to get the grease on your mower parts and mess up the paint adhesion!

[awemawson]

You'd be amazed how often you wash your hands slicing and vacuum packing bacon 

The slightest bit of bacon fat stops the heat sealing working, and handling a chilled flitch of bacon through the slicer certainly gets you cold and slippery 

Planning and work flow are the keys to sucess, and a good scrub down of the stainless steel work top afterwards 

[Will_D]

 Hi Andrew,

Would ye not put a few packs in the "for sale section"

 

[awemawson]

They'd not arrive frozen Will 

So this morning I prettied up the gearbox. First a coat of primer having washed it down well with thinners. Then while that was hardening I re-made the adjuster for the belt tensioner, as the thread on it was badly mangled - just a bit of M20 studding that compresses a spring. The idea is that the spring is compressed fully to allow the belts to slip on, then the threaded rod is slackened off letting the spring bear on the side of the jack shaft pivot putting belt tension on.

Then back to the gear box for a coat of top coat (RAL 1007 JCB Yellow)

[awemawson]

Now talking of belts - there is an oddity 

The four sheave 200 mm o/d pulleys are marked SPB - which is a Vee belt shape specification (16.3 mm wide and 13 mm thick) Of the four belts that came with the machine, three are marked 'Turner' (the maker of the flail) but measure as 13 mm wide and 15 mm thick so are not 'SPB' belts. The fourth belt is a Trellborg and seems to be marked SPB 1600 but measures roughly the same as the other three. Also there is evidence that the belts have been bottoming on the sheave grooves as they are shiny.

I suppose that it's possible that all the belts started off correct width and have worn uniformly over the years, but that seems a bit fanciful frankly

I'll probably assemble it with these belts and then measure up to see a true o/d to allow me to find a proper 'SPB' Vee belt set to fit.

[awemawson]

I wanted to bring the newly painted gear box into the heated part of the workshop for final paint harderning, and decided the safest place to put it was back on the flail as horizontal surfaces all seem to have disappeared 

[awemawson]

So a bit of a clean up on the jackshaft pivoting arrangement, loads of CopperEase on that pesky spline on the drive input U/J and I popped the jackshaft back into place.

Then I was about to set too and fit the pulleys on the main flail shaft and the jack shaft - they are retained with taper lock bushes. Both bushes were broken when I dismantled it, and as far as I can see the problem was that the drive keys were too thick. They fit the keyway widthwise, but there is no head space at all radially, so as the bush tightens it is being bent over the key. Reading up on taper lock bushes, they always should have radial head space on the keys:

http://www.fptgroup.com/Taper-Lock-Bush-Installation-Video/

Measuring the shafts and keys to decide how much to skim off on the surface grinder it dawned on me - they were NOT the same diameter - the flail shaft is 2.5" and the jack shaft is 2" so I'd bought the wrong bush for the jackshaft - arggh 

Off to the web to order another ....... more delay 

[awemawson]

So having ordered the replacement (correct sized I hope  ) bush not much more I could do. I've titivated the key for the correct sized bush and given it 10 thou headroom radially which means that I can loosely fit it on the flail shaft, but can't tighten it down until the other pulley is in place, as they need to be set for correct axial alignment or it'll chew belts.

...oh I dunked all those flappy plates that I squashed flat into a bucket of warm citric acid to remove the surface rust. Not sure there's much point in painting them - a decision for another day.

[awemawson]

So Tuesday started fine with a good forecast of dry weather all day. Ken the Blaster came just before lunch and blasted the remaining bits which is a major 'good thing' 

Then I set up for spraying them - small bits hung on wires, and the bigger bits lying on pallets. Started with the three boxy bits up side down letting me spray them in primer inside - the intention being that when inverted the outside could get primer and top coat but the inside can stay in primer.

I got as far as doing the insides, and the heavens opened  Just a brief shower I thought as it brightened up. I set too blow drying the bits with an air line, which worked quite well, until the deluge returned 

Fortunately the primer dries very quickly, and by the time I managed to pull a tarpaulin over the bits it had already dried. No doubt the freshly blasted bare steel will be lightly covered in rust by the morning, but nothing I can do about it at the moment from the sound of rain on the workshop roof 

[awemawson]

So it stopped raining, but was still rather looming and gloomy so I decided to drag everything into the welding shop to complete the job. Once inside I blew everything off with an air gun, then directed a 4 kW blower heater on the bits for a while to ensure that they were properly dry.

As expected, the highly reactive freshly blasted steel had lightly rusted in places, so a quick rub down with emery paper and a dust off left them ready for resumption of priming. I set up a few strategically placed gash sheets of hardboard to minimise the overspray onto adjacent things and gave them a spray.

As I write they are virtually dry already, but the fan heater is now encouraging them, and hopefully after supper they can have a first top coat of JCB Yellow 

[awemawson]

After supper the fan got turned off and I set too putting on the first top coat.

I was probably rather too enthusiastic with the thinners as there are a few runs, but the bits are certainly looking much more yellow 

[RobWilson]

Missed a bit 


Rob

[awemawson]

Missed a bit 


Rob

It's ok Rob, one of the runs will dribble over it 

[RobWilson]

   

Rob

[krv3000]

brill

[awemawson]

Those fiddly bits all got a quick blow over again this morning, and when touch dry I brought them into the heated workshop for hardening off.

Just as well I did, as I'd just finished when the Brundles lorry turned up with a load of  6 metre 50 x 3 flat steel bar for my plasma table and a length of 14 mm round to re-make that 'flappy plate' pivot that's bent like wiggly snake.