Why wont my flail drum turn?

[OregonFarmer]

I've got a Befco H80 100 flail and it has been working great this spring - until today. It is hooked to my IH 674 2wd tractor and it's 62hp seem to do a great job spinning this flail through tall grass, blackberrries, brush, etc. I was mowing some 30" grass today and the flail drum stopped turning. After cleaning up the drum and putting the machine up on a concrete pad, removing the belt cover, I did some detective work, starting at the tractor. I discovered the PTO shaft on the tractor was turning, the drive shaft to the flail was turning, the grooved shaft that comes out of the gearbox was turning but the horizontal shaft and belt pulley that spins the drum was NOT turning. When I turn the belt pulley by hand (tractor off), it turns easily, belts, drum and all. In fact, even the tractor PTO shaft turns easily when I turn the pulley on the flail, either direction. This does not make sense to me.

Before I tear off the gearbox and take it apart to see if something is busted inside, I wanted to hear what you thought might be going on here, so fire away.

I thought perhaps there was a shear pin on the drive/PTO shaft that has sheared. Other mowers I have owned have such a pin, but there does not appear to be any visible shear pin on this Befco Flail.

Thoughts?

[charleyfarmall]

So the output shaft from the gearbox turns with the pto shaft, but the horizontal driveshaft and pulley that drives the belt doesn't. what couples the output shaft to the horizontal driveshaft? On my Mott it's a sleeve. I don't know what it is on my caroni, i've never looked at and that mower isn't here.

The horizontal shaft is inside a protective tube isn't it? What ever the coupler is, it has failed. I'm guessing that that you need to unbolt the gearbox and take it off because that tube is a welded part of the frame isn't it? The problem isn't in the gearbox.

Nice mower by the way.

[OregonFarmer]

Turns out my flail drum was not turning because the key in the main horizontal drive shaft had completely disappeared. It was gone and only dust left in it's place. I could not see the shaft was turning without someone else to observe the end of the shaft. I knew the pulley was not turning under load but could not see the shaft turning. Also I found this is a metric rectangular key stock. Weird. It is 8mm by 12mm by 20 mm. I got an american key stock and ground it to the right size as metric key stock is very uncommon here in Oregon.

Thanks for the help. I am flailing again and now am trying to get the belts on the mower tight enough to flail 6' tall fescue. Turns out this Befco flail has a modified belt tightening setup and has no spring to keep the belts tight. At least they are turning now...

[J_J]

Can you add a spring to help with the tension? Try sharpening the blades, or reversing them.