Howard 350 Rotor Drive

[vhgmcbuddy]

Hello all,
As a keen gardener with some old machinery in the shed I have used the club forum a few times in the past but have been tidying up a Howard 350 over the winter and now need some advice that I can’t find in the archives. The Howard is running well and everything seems to work but when I put the rotors under load the rotor selector drive gear jumps out of engagement with the rotor idler gear. I have not split the chaincase or removed the gearbox yet but by removing the selector fork I can see that the selector moves back and forth along the splined shaft and seems to engage nicely with the idler (though the idler has some damage to the teeth).

Does anybody know is there any mechanical interlock within the gearbox that holds the rotor selector drive gear in position or is it simply held in position by the selector fork? Also my soil is fairly heavy so could it be that I am just trying to run the rotors too deep? I have seen a used idler gear assembly on ebay for £50 but don’t want to splash out that much if in fact that is not the problem.

[wristpin]

Dealt with a few years ago and from what I can remember the problem was caused by wear on the dogs causing them to ” cam out” under load and the only answer is new components. What I also remember is that when offering the gearbox back onto the chain case there’s a little shim/thrust washer on one of the shafts that needs to be firmly stuck on the shaft with heavy grease to ensure that it stays in place. Once the gearbox is back on there is no way of checking !

[vhgmcbuddy]

Thanks Angus, As far as I can see from the parts diagram and by peering in through the selector opening there are no ‘dogs’ or other mechanical locking device to hold the rotor selector drive gear in position once it is engaged. The rotor selector drive gear and the idler are straight cut and the rotor selector drive gear slides on the shaft to mesh with the idler.

I would have expected to find some form of mechanical locking but I just cannot figure it out. Any information would be greatly appreciated.

[wristpin]

As I said, it was a while ago ! Anyway I’ve had a look at a parts list and you are correct, no face dogs but a sliding gear. Similar situation applies. If, over time, operators have been a bit impatient and attempted to engage the rotors before the drive train was stationary the mating surfaces of the gears will become worn and will tend to be forced apart under load.
I will scan the relevant pages of the manual and post them later – they may be of assistance.

[Anonymous]

I have never had or worked on a 350 but of all my howards (18) it seems to be a common problem of rotor pinion gears wearing out of alignment and jumping or working their way out. Even on the gems the wheel gear drives seem to do it also. The little australian built terriers were shocking for it. I haven’t come across any that lock into place with out the selector itself locking it in. Problem is you have to change two gears not just the pinion one as they wear both gears uneven. That is unless you can turn a gear around?

[wristpin]

Not sure whether these parts illustrations are what you already have but they may be of use to you or others.

https://www.dropbox.com/s/0jbgz39rknbrb90/HOWARD%20300%203500001.pdf

[vhgmcbuddy]

Thank you all for your replies. It seems to me that wear in the bearings and gears themselves must have built up to such a point that the side force produced by the misalignment overcomes the selector and ‘spits’ rotor selector drive gear out. I’ll have to split the chaincase and see what state the components are in.

[Author]

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