Rotary Cutter Cracked Deck Repair Advice

[dux]

Ugly as it is, I got this old 6' woods cutter for a song and it has served well for a couple years. It had been 'repaired' a number of times by previous owner(s). Now it has (again) developed cracks in the reinforced section of the deck where the gear box mounts. The cracks allow the mount to flex enough that the blades and arms strike the underside of the deck.
The section appears to be 5/16" thick. I'd appreciate any advice you all have to offer about how to fix it. I'm no expert welder, but i'm considering taking this on myself... though I don't have many fabrication tools beyond an angle grinder and and a few drills... Some of the other threads here show the entire section being cut out and replaced... if that's whats necessary, i'll probably take it to a shop...

Thanks in advance.
-dux

 

[Gary Fowler]

Due to the extensive cracking and fatigue of the existing metal, I would cut that whole section out and replace with heavier material and complete with some diagonal bracing like flat bar or angle stitch welded on top and extending to the edge at each corner. That should stiffen it up.

The reason it keeps breaking is poor repairs to original small crack where the repairer just laid a not too good, low penetration weld on top of the crack. For crack repair the weld has to be full penetration and is best done welding from both sizes. If you leave any of the crack under the weld it will just crack back thru the weld again.

 

[Mark @ Everlast]

Looks like repairs may have been done with a 110MIG...either that or it was used with really low settings to make the repair. I'd just get a piece of heavy plate to go back in the formed metal slot. A lot of companies use a heavy piece of flatbar in that application. Cut it out, and weld the plate back in.

 

[Arc weld]

It looks like the cracks may have originated at the bolt holes. Perhaps the original bolts came loose? I'd cut it out past the cracks and replace with new plate.

 

[Brad_Blazer]

I've seen arcs traced by the blade tips but that's the first time I've seen one traced by the pivot bolts.

If you can remove the blade carrier and pull the gear box it should save you some money even if you take it in for the repair. If you can't you're taking it to a shop for the whole shebang anyhow. Bring in your pictures for an estimate so you can make the repair/replace decision.

Whatever the dimension of the top of the formed plate between the verticals, e.g.10x24, I would get a piece of plate that size by at least 3/8" thick. Cut away the old plate leaving enough of the original edges to support it so the gearbox is at it's original height. You don't want it any higher because the blades can swing up a little at the pivot bolts and the tips will hit when you hit a bump no matter how rigid the repair is.

You could sketch up the replacement plate and have a shop fabricate it for you if you don't have at least a full size drill press to spin a hole saw for the shaft and a big bit for the bolt holes. A place with a CNC plasma should be able to make it for around $100.

 

[brown40]

I think the 'bird poop' and metal fatigue is covered--I'd second the solid plate rather than formed carrier.

If it was mine I'd cut it out and make a square patch patch 'longer' front to back that the original design--tie it into the deck so forces are working welds and steel across a greater area when the box gets torqued.

If I had a cutter--a circle patch would be ideal and 'slick' looking too.

The access panel would outline the back if you patch with a square--it would stick that much further in the front.

I like to see six bolt gearboxes--they seem to hold up better than smaller four bolt ones--I suspect because each spans 60 degrees instead of 90--better force distribution?

 

[dux]

Thanks for all the tips. I'm going to pull the gearbox and take it to a shop. I'll let you know how it works out.
Thanks again!

 

[crazyal]

Does the cutter vibrate excessively? It could be that you have a vibration problem that's stressing the metal. Maybe a bent or damaged blade? As for repairing the metal, I would do as the others have said, remove the bad metal and replace it with new. If you have a 4 1/2" grinder you can buy some thin cut off wheels and just cut the bad metal away.