Hyundai Tine repair.

[Colin]

Hi,

Bron kindly bought me this Hyundai 139cc HYT140 tiller/rotavator brand new for Christmas last year and its a beauty; eventually the ground dried sufficiently to use it in anger; I had spade dug the entire area to be rotavated removing many roots and a mountain of stones but after a session whilst cleaning the rotavator I noticed a tine was displaced. The tine had pivoted around its securing rivet rising out of the indents in the driving flange.

After a struggle I managed to force the tine back home but when used again the same thing happened. Today I decided to sort this problem out once and for all. I removed both tine assemblies and in the workshop arc welded the tines to the driving flanges; a simple and quick repair to anyone with access to a welder. Each tine unit is held in position by a single 8mm set screw and locking nut. I always spend time after using any of my kit to clean and lubricate if needed then it's ready for action.

Once I got the knack of using this rotavator its a pleasure to rotavate rather than spade digging.

Kind regards, Colin.

My new toy.

Tine assemblies.

Tine assemblies removed ready for repairing.

The tine at the top of the picture should be vertical but it's pivoted on its rivet; care is needed forcing one of these tines back into position due to the force required; not the easiest of things to handle.

A quick and easy arc welding job; a going over with a wire brush and a blast of black paint from a rattle can its now better than new.

 

[DirtMechanic]

Dear @Colin,

The tines are generally replaced as they wear and are sharpened occasionally. Welded, the whole assembly must be replaced. This will now become an interesting maintainance issue. I generally use a flapped metal sanding disc on my grinder for general ground working tools, so perhaps stone strike damage or other touchup could be accomplished similarly.

What concerns me is transmission damage and stripping of driveshaft gears or other issues as there is no give nor a shear pin that I can see. I got the impression the detente was a safety feature for the drive where one blade sticks but others do not and perhaps the shaft would break or bearings get crushed under pressure from the binding under high torque conditions. Perhaps a soft aluminum or copper shear pin could have been installed instead of welding?

 

[Silentrunning]

I’m afraid that DirtMechanic if correct. It sounds as if that was a sacrificial component meant to slip and take damaging torque off the transmission gears. The transmission is the weak link on most rototillers.

 

[Colin]

Hi,

Thanks for your comments which I very much appreciate. I was taught the old fashioned way as an apprentice mechanical engineer 55 years ago and I do appreciate your valid concerns DirtMechanic so thanks for speaking up; I did give this problem some thought before welding on the lines you mention taking into account any possible later collateral damage?

If the transmission does suffer I'm more than capable of repairing it as well. In order to replace a tine then the rivet would require grinding or drilling out and the new tine replaced with a set screw and nut? Welding the tines doesn't mean the tines cannot be removed if one should become damaged; my angle grinder enjoys removing weld. The tine which was displaced I think jammed on a root and this stopped the shaft turning but no damage was caused to the shaft or transmission because the clutch slipped this being the safety cut out not the detents; the tine being displaced still stopped the shaft rotating so it's highly unlikely the detents are there for this reason? A shear pin for this application wouldn't work because if the pin sheared the tine would still prevent the shaft rotating because of the securing rivet? A shear pin is to break connection?

Sharpening the tines is something I doubt I'll ever do unless one becomes damaged but so far they've come into contact with big stones without the slightest damage to them.

The transmission is indeed a weak link Silentrunning hence the clutch which slips should the tines jam against anything. I did actually consider adding an extra fastening like a set screw and nut to each tine but having already suffered lots of tine fouling because of grass sods the set screw heads and nuts would perhaps give rise to more jamming hence my decision to weld.

My spade used for digging never needs sharpening in fact the more its used the sharper it becomes taking on a nice polish to the blade. If the tines do ever need touching up after coming into contact with something solid I've got a good selection of sharpening kit including engineers files. Unless a tine becomes damaged wouldn't all the tines wear roughly at the same rate so if the time comes when the tines are badly worn the whole assembly would need replacing anyway? The tines jammed many times against the bigger stones without any damage being caused; smaller stones tend to jam between a tine and the gearbox but this simply causes the clutch to slip without damage? I can make the new tines and the whole tine assemblies and possibly new gears if ever needed; my workshop is well equipped but I realize not everyone has my workshop or experience. Please see the pictures below; I was honoured with top restoration in 2009 having dreamt up a new way to cut gears on a lathe; I'm not smart and I hope I don't appear smug in any way but I had good teachers who taught me so well.

I'm very much aware my rotavator has a clutch and the clutch slips if the shaft is prevented from rotating otherwise I would never have welded.

Kind regards, Colin.

 

[DirtMechanic]

A clutch is an interesting development, where so many of those machines use a belt in a gear reduction to increase torque at a lower rpm rather than drive a shaft at the engine rpm. Inherently that reduction unfortunately becomes a force against which a binding tine forces itself, and thus every component between the tine and the clutch or reduction gear-belt.