In May 2025, I spotted a rather unusual ‘Mower Conditioner’ on Facebook Marketplace. In retrospect, it was probably overpriced, but I needed to cut the field, and this mower was local enough to collect and definitely ticked the vintage equipment box. I bought this before borrowing the Spearhead Flail; however, this mower conditioner is better suited to cutting the grass crop rather than pulverising it, the way the Spearhead does. This article is about the John Wilder Mower that I collected, and the repairs carried out this season (2026) to get some reliability back into the mower.
The Wilder-Rainthorpe “Multi-Masta” Chopper
The formerly bright orange ‘mower conditioner’ that I collected back in May 2025 was the “Wilder-Rainthorpe Multi-Masta Chopper”. I’ve found information about this particular mower rather scarce, which perhaps is not a surprise when the manufacture of these mowers ended in the 1960’s.
The original Multi-Masta was intended as a heavy flail for reducing thick brash in forestry or road verge conditions. The mowing system was originally designed by Lincolnshire farmer Jim Rainthorpe and manufactured by John Wilder Ltd.
The most common variation of the Multi-Masta system was the ‘Straw-Masta’, which was an inline-towed variant. There was also the ‘Haulm-Masta’ for topping potatoes, and the ‘Sila-Masta’. The variant of the Multi-Masta system I have is the ‘Flail Mower Conditioner’ with offset towing and a heavy rear roller for the ‘conditioning’ of the grass stems after the grass is cut.
Reliability Issues
Since collecting the Wilder-Rainthorpe Flail Mower Conditioner, it has been riddled with issues. The tin work is obviously showing its age at seventy years old, but there are no major failings of the mower body. When I first brought the mower home, it was completely missing its skirt in front of the flails, but this was quickly resolved with some heavy rubber matting.
The bigger issues, however, were with the drive line from the PTO to the gearbox. The unusual rectangular shaft was very worn at every joint. Beyond being incredibly noisy, the drive line could be seen visually jumping around.
At the end of the 2025 grass season, the driveline actually fell apart, more than once. There was no way that I could use the mower again without some serious repair work.
Restoring the draw bar
Most of the issues with the drivetrain vibration actually stemmed from the amount of wear throughout the draw bar and drivetrain supports. The easiest way to tackle these issues was to pull the draw bar out of the machine and bring it into the workshop.
Removing the various brackets was surprisingly easy, despite the corrosion on all the bolts and nuts. Just pulling the fixings out of the draw bar showed how much wear had accumulated over three-quarters of a century.
With the draw bar disassembled, the old orange paint was stripped back using the angry brush on the angle grinder. While I was fully masked up, expecting the paint to be lead-based, I really wish I hadn’t sent the orange dust all over the workshop!
Once suitably prepared, the whole draw bar was coated in a Vapourmatic red oxide primer. I doubt this is as good as traditional red oxide primer from a time before chemicals were controlled, but having been using it for more than five years, I’m really impressed with the coverage and rust resistance.
Then I gave the whole lot a top coat of Kramp synthetic enamel in a shade called Abbey Orange. In my defence, in the shop, this looked like a much more subtle colour, and it was the only orange paint on the shelf. It’s a little brighter than the original paint. While supposedly brushable, the brush and roller did a terrible job. In the end, I broke out my antique air spray gun and managed a reasonable finish.
Towing Tongue
One of the most worn-out parts on the mower was the connection between the machine and the tractor, which I will lovingly call the towing tongue. The cranked 25mm flat piece of steel had become rather thin in places, and the draw hole was no longer round, but more egg-shaped.
To cure this issue, the towing tongue was cleaned back to bare metal and the surface brought back up with layers of weld from the MIG welder using 0.6mm wire. Before starting to build up the metal, a torch was used to heat up the metal to improve the bond with the first few layers of weld.
There wasn’t too much wear on the top side of the towing tongue, as it does not sit in close contact with the tractor’s hitch. Once the tongue flats were built up, material was also added to the elongated hole, working from the middle of the metal thickness to the outer edges.
All ground back to flat, and both sides of the tongue were pretty much parallel, possibly for the first time in a long while. The hole for the pin was also drilled back out to a nice round 25mm. I chose not to harden the steel, as I would much rather have the tongue wear out than the clevis on the tractor.
Propshaft Repairs
During the previous season, one major and quite dangerous issue I faced was the propshaft actually falling apart. The outer shaft of both the long and short PTO bars was a simple round-section tube with an adapter welded onto the end to accept the rectangular (32mm x 35mm) inner bar.
The welds between the tube and the adapter were a serious weak point. I expect this failed due to fatigue caused by excessive vibration. To give a true farm fix, I actually used stick / MMA to weld the parts back together as I figured this would get the most metal in and the best chance of avoiding the same failure.
The cleaned and welded outer sleeve of the PTO was then treated to a couple of layers of Kramp acrylic mat black paint. Probably a little excessive for a power take-off shaft, but it should help with cleaning in the future.
The long shaft has a ‘normal’ six-spline output, which is supported by a bearing in a universal joint. So, like the short shaft, the adapter was rewelded into the end of the pipe and the whole metal surface stripped back.
And to finish, the whole PTO outer sleeve was painted with the same black paint.
Propshaft Carrier
The propshaft intermediary carrier is made up of a bearing set in a ‘U-section’ holder, which is held into the propshaft carrier housing on a single bolt. This allows the propshaft to ‘swing’ up and down. The carrier is then attached to the draw bar through a single bolt, allowing the carrier housing to swivel left and right.
These two axes of movement allow the propshafts to be aligned to the tractor, but once they have a lot of play, they induce vibration and failure. The bearing that was in the middle of the system was long past its best. Although it didn’t fall apart, it was very stiff and did not rotate smoothly.
Fortunately, it was a fairly common size, 72 mm x 35mm x 17mm, and the £6 replacement was soon installed, allowing the PTO shaft to rotate smoothly.
The bolt that held the propshaft carrier to the draw bar was completely seized and had to be cut off. The holes here were both worn into an oval and were drilled out to the next metric size. What I hadn’t realised is that the original holes were actually different sizes, with the bolt having a step in it. Hopefully this will hold up.
Reassembling the draw bar
Finally, after a few weeks, the draw bar could be assembled. Two of the most expensive parts in the rebuild were the propshaft guard and the new bolts used in the reassembly. The bolt cost might have been a result of ordering ten pieces of everything, just in case.
When assembling the propshaft carrier assembly in the standard position in the draw bar, I felt there was not enough insertion of the inner shaft (story of my life!). My simple solution, after finding it impossible to order 32mm x 35mm bar stock, was to move the carrier back two inches with some new holes.
The improvement in play in the drive line was immediately obvious. Just turning over by hand was so much easier and smoother, without the grinding and banging it used to have. Job done, I hope.
Sharpening the Flails
One last thing to prep on the mower was to sharpen the leading edge of the flails to get the best cut in the field. I’ve not yet been able to find any replacement flails, so I need to be careful about how much material I take off.
Once hooked up to the tractor, I could use the hydraulics in the John Wilder mower to raise the whole ‘Multi-Masta’ off the ground. I learned long ago on hydraulic Citroens never to trust fluid pressure alone, so an axle stand was placed either side of the body.
A fairly terrible picture, unfortunately, but armed with an 80-grit sanding disc on the cordless grinder (and ear defenders and visor), I climbed into the belly of the beast. There is actually a lot of room in there, and sharpening the leading edge of the flails was a surprisingly pleasant experience.
Ready to bring in the grass?
While the proof will be in the pudding, after a walk around with the grease gun, the vintage Wilder-Rainthorpe mower should be ready to bring in this year’s first grass crop. I’m confident that the work that has gone into restoring the mower’s drivetrain should last for at least another 50 years, although I would rather have a 90’s disc mower than this flail mower.