the Walnut Diary

This review is the product of seven years of mowing 25 acres of tree seedlings on our property. After wearing out a Walco 60″ rotary mower inherited from my dad (replacing one set of blades and three gearboxes), I bought a new 60″ Rhino to run on my 35 hp TAFE tractor but discovered that many of the rows in the new plantings were too narrow for the 5′ 6″ tractor to travel. So I bought a 1980 Bolens G174 with a track of 38″, 4WD, suitcase weights, a 17 hp diesel, and a separate overrunning clutch to cope with the the Braber’s flywheel effect. A 48″ Braber rotary mower mounted neatly onto the 1200 lb tractor and I gained easy access to the shrinking rows between the trees.

The Braber 48 likely had about 200 hours on it when last summer I demolished the gearbox by bellying onto a rock. The bottom of the gearbox casting sheared right off. Braber replaced it under warranty, but I had to do the mechanical work myself. Regardless of lubricant choice the new gearbox is too noisy and damages my hearing, even with earmuffs. I can’t see going deaf to that racket for another ten years, so I’ll probably buy a better mower soon.

But accidents happen, and maybe the replacement was a lemon. My real beef with this mower has to do with its gear ratios. The Bolens G174 has 3 pto speeds, and I chose the middle gear which provided 750 rpm at the shaft. This worked well. But then I bought a much newer Kubota B7510HST with a 540 pto. This produces a lousy cut in long grass with this mower. The 5′ Rhino’s cut is vastly superior.

So I looked at some parts manuals. There are two 40-45 hp gearboxes available, a 1:1.4 ratio, which this one is, and a 1:1.9 ratio* which would likely work well on my Kubota. (Big mea culpa here: the replacement gearbox is a 1:1.9 model.)*

So if you have a small tractor with a 3 speed PTO, select the middle gear and this model will do you well. If you have a more modern tractor and want to do a lot of mowing, find a mower with the 1:1.9 ratio or get a 60″ machine. The tip speed just isn’t there for a fine cut unless you turn the shaft more quickly than 540 rpm.

This morning I shattered a blade on another rock and was pleased to find that TSC USA stocks them. Tuesday with any luck I’ll slip across the border to Ogdensburg and get the parts I need.

Update, Sunday, 3 August, 2014:

A lull in the action prompted me to head off for Ogdensburg and pick up the 3″ X 18″ blades they had in stock. There was a set of 3 1/2″ X 18″, but the box didn’t look that wide. I opened it up. Two 3″ X 1/2″ X 18″ looked back at me. What’s a little typo on a box between friends, eh?

As the surviving original blade measured about 17″ and the replacement was 18″ at the same point, I had bought the blades on the assumption that I would have to cut an inch off them. The saw was all set up before I examined the dead one more carefully. Though the metal was dark and smooth, it didn’t look as though I had been at it with an angle grinder, and I had done a lot of sharpening on those blades over the years. Seems the rock strike had broken one blade in two; the other had lost an inch off its end in a very precise split, as well as bending all out of shape.

I had bought the correct blades after all. They fastened right on with the bolt kit on the shelf beside the blades.

I found the Ogdensburg TSC quite an impressive store with a smart, helpful guy on the service desk.

The much-maligned Brader 48″ rotary mower may again see service> If the blades work well I may just replace the noisy gearbox with a 1:1.9 model. (See above).

UPDATE: August 5, 2014

The rotary mower had to be readjusted to allow for the larger offset of the new blades. I raised the chassis of the cutter an inch and adjusted the rear wheel and chains at the front until it cut properly, if producing a somewhat taller cut than before with the old blades.

As soon as the paint wore off the blades, the cut improved immensely over the old blades. It wasn’t just sharpness. The old blades, I am convinced, had been banged out on a forge by a blacksmith who had no concept of how the things were supposed to work. The sharp part of the blade was on the high side of the twisted blade, not the lower side. Instead of sucking the hay up to the blades, the old blades blew it down after cutting it.

So now the mower cuts much better than before. It is also quieter and more agile in conjunction with the tractor in its taller stance: the rear wheel pivots much more easily.

I feel I may have mistreated TSC in my review of their 4′ rotary mower in that I ascribed failings to their model which may well have been the result of bungled blade construction by a competitor. In the review I rated the generic machine a 3/5 when 4/5 would have been more appropriate. The TSC blades and bolts were fine, at least before their first encounter with a rock.

UPDATE: 28 January, 2015

In retrospect, I realize that the problem with the blades is that they are made of soft steel. An impact with a rock will bend the blades up. Repeated impacts will result in the reverse-shape I have referred to above.

The conclusion from this, I guess, is that the Brader machine with its low-carbon blades is a decent grass-cutter, but if the machine sees rough use around rocks, the owner should be prepared to replace the blades with a new set. At $58. per pair at TSC (USA), the price is not exorbitant.

I should also remark that the replacement gearbox on the Brader has gradually grown less noisy, though it’s far from quiet. One tip for anyone replacing the gearbox on this model: bolt it on with the nuts up, rather than down. Then if one or more nuts come loose on the unit, the change will be immediately obvious to the operator, and with a little luck can be tightened up immediately with a wrench, instead of requiring the disassembly of the machine to re-tighten the bolts.