How much damage am I likely to have done to my new tractor?

[tallguy104]

Determined to make it last a lifetime, I've been religiously cleaning, greasing, servicing and maintaining my new Kubota B2301 since I bought it earlier this year.

I've been warned that you never want to "stop-dead" the PTO during operation, hence why rotary-tillers and such have shear pins/slip-clutches.

Yet somehow I've managed to "stop-dead" my new tractor 3 times by hitting immoveable objects with my mid mount mower. It appears the MMM does not have a shear pin or anything. One time was on a low tree stump which I stupidly thought was low enough for the mower to go over (no it was NOT). The other two times were on large branches which had come down in the long grass, which I failed to see. In each case BANG the blades stopped-dead and instantaneously stalled the tractor

The tractor still appears to be working, however I can't stop cringing as I wonder how much damage I might have already inflicted on my new baby.

Can anyone tell this lay-man just what kind of damage / premature wear I may have caused?

 

[workinonit]

Probably much more damage to the mower than your tractor. I've stopped my 90 HP JD twice since I got it. Hasn't affected it.

 

[4570Man]

Bending the blades is the most likely problem. Aside from that it’s likely nothing happened.

 

[CausticUrbanCoast]

Diesels seem to be rather more forgiving in this area.

It is not something you would want to have happen mid-spark with a gas engine.

 

[CobyRupert]

Other than bending the blades, if something broke, you’d know it. Otherwise, it’s fine.

 

[Roadworthy]

You could have bent the blades but you could also bend a spindle and have the blade hitting something underneath or cut at an angle.

 

[rademamj1]

From my experience, you have not done any damage to the Kubota engine, but your mower blades probably received some damage. Basically I would look for any blades that are out of alignment, and these now create noticeable vibrations. Blade replacement is recommended.

I also highly recommend you walk your mowing areas looking for debris and stumps. The higher the grass, the more you should walk it. Normally I keep my field grass low, but after long vacations, I walk the field and look for any new debris. I found a new Rabbit mound this way, and flagged it for avoiding. Nothing worse than hitting baby rabbits.

 

[dadohead]

Dang... you've unknowingly given your mower the 'stake test'. It's a safety standards test we do when developing mowers to make sure nothing flies out or skitters across the ground when a mower contacts something hard... injuring someone.

In this country (ANSI B71.1 test) a 1" steel rod is fired up from the test cell floor into a running mower snuffing it instantly. The tractor/mower is surrounded by target paper. Parts can't fly off and contact the cardboard in the target area or drop parts onto the floor to pass. Each spindle is tested. The steel stake will have a big 'bite' cut into it and can be bent back 30 deg or so. Each blade will have a large 'round' smashed into the cutting edge too.

Unfortunately, a typical casualty is also a bent spindle pocket. I would lift the discharge chute (or better yet drive your tractor up onto car ramps) and inspect the blade plane alignments at the blade tips. It's easiest if you can de-tension the secondary drive belt allowing the blades to spin independently allowing you to easily get the blades 'tip-to-tip'. You can usually force one blade around to get them together if you can't de-tension. Assuming you have a 3 spindle belly mower, you'll be checking 2 places: LH blade to Center and Center to RH blade. Once you get 2 blade tips together, you're looking for the blade planes to be no more than 1/8" difference in height. You have to spin each blade around 180 deg to check (4 inspections before moving to the next blade pair).

If you find a blade pair that doesn't align in height and the opposite tip is out of alignment by the same amount... you probably have a bent spindle pocket. I would install new blades and check the alignment again. A bent spindle pocket is a bigger deal but dealers usually have a means to straighten one back into position. This is not a home shop fix. If your land is rough enough that you're hitting objects.... maybe you should think about trading the mower for a rotary cutter?

 

[tallguy104]

Ok thanks folks. I'll pull the mower deck off and have a good look as suggested. I'll definitely be walking my fields before mowing in future. It's actually only been 2 weeks since I last mowed, but its been so hot and humid here the grass is already 18 inches high!

Aside from the strain on the mower, can someone please explain to me what having a tractor stop-dead like this can do to the tractor/engine? What tractor parts are being stressed exactly? What kind of repairs might I be up for if they keep doing this? (hypothetically...I WON'T keep doing this!!)

Also, why doesn't this brand new Kubota mid-mounted mower attachment have a slip-clutch or shear pin??

 

[rademamj1]

I can't ever remember seeing a slip clutch on a mid-mount mower or any zero-turn for that matter. Probably because your not expected to be hitting debris on a continuous basis. You need to move up to a rotary cutter to find slip clutches and shear pins on your mower.

I have been mowing with Gravely Proturn 460, a Kubota GR-2120 and a Kioti CK4010 with medium duty rotary cutter for several years now. Any high grass with trees, always requires a short walk around prior to mowing. Especially if you have large old trees. Always Flag or remove debris. You can even drive your mower around looking for debris....without the PTO engaged. Its like a quick recon of the area before mowing.

 

[oosik]

I've never hit anything that has "dead stopped" my JD X570 mmm. But since I insist on "mowing" my pocket gopher mounds - quite a bit of hidden gravel.

Every spring I resharpen/balance the three blades. I take special care to grind out or sharpen the nicks in the blades also. Life goes on ...............

 

[ScotNH]

I’m not familiar with that particular mower, but with my MMM, I assumed the belt between the blades and the PTO would slip before doing serious damage.

 

[dodge man]

I don’t think I’ve had that happen with my current JD but I did with my previous Kubota BX. It never seemed to hurt it.

 

[sea2summit]

Also, why doesn't this brand new Kubota mid-mounted mower attachment have a slip-clutch or shear pin??

Because it's got a belt? I can't remember for sure, is the center one direct drive off the gear box?

 

[dougtrr2]

I was under the impression that the cupped washers/nuts holding the blades on also acted as a slip point.

Doug in SW IA

 

[Rdrcr]

I had it happen with my B2601 w/60” MMM when I hit a hidden stump. No damage to tractor or mower.

Mike

 

[dadohead]

Aside from the strain on the mower, can someone please explain to me what having a tractor stop-dead like this can do to the tractor/engine? What tractor parts are being stressed exactly? What kind of repairs might I be up for if they keep doing this? (hypothetically...I WON'T keep doing this!!)

Also, why doesn't this brand new Kubota mid-mounted mower attachment have a slip-clutch or shear pin??

I seriously doubt that you've hurt your tractor in any way. I'm a retired JD tractor/mower engineer. The reason mid-mowers don't have a mechanical 'fuse' in the system is that it wouldn't help. Most of the system's energy is in the running mower; the drivetrain is seeing high rpms but low torque. When the mower is shock loaded, most of the reaction forces go to the blade, spindle, and spindle pocket... a slip clutch wouldn't change that. Unless you have a 'timed' mower, the blade joint is probably just a self-tightening bolt. There is a little slippage but not much. Much of the engineering in the blade joint is to deal with the inertia in the other two blades at impact so they don't unscrew themselves, fall on the floor, and fail the stake test.

Good idea to pull the mower for inspection. Fingers crossed!

 

[CausticUrbanCoast]

Aside from the strain on the mower, can someone please explain to me what having a tractor stop-dead like this can do to the tractor/engine? What tractor parts are being stressed exactly? What kind of repairs might I be up for if they keep doing this? (hypothetically...I WON'T keep doing this!!)/QUOTE]

As diesels use compression to combust, stopping it dead means it is unable to combust on the cycle (so you do not shock the pistons and rods). Diesels also have the capacity to tolerate running backwards if the situation arises.

You stand more of a chance of damaging your transmission or mid-PTO drive.

And everyone is correct, a belt will typically fail before any shearpin will, and if tensioned properly, before any metal damage (aside from blade edge usually, old and rusting decks will have the towers destort the deck).

 

[IndyIan]

My buddy broke the pto shaft on his little kubota with a 4' bushhog hitting a few Christmas tree stumps every year. But it had over 3000 hard hours on it, mostly mowing using the full hp so I think your odd stoppage will be fine.

 

[PILOON]

I was snow blowing and the auger found a scrap of 2 x 4 and stalled the diesel engine.
Shear bolt did not do its job!
While very concerned , I have not observed any detrimental effects but I still worry about long term effects.
Mind U over the years I have sheared many bolts on my gravel drive and no effects.

Worst area is where the city plow creates snow banks at my entrance since the road is gravel based and who knows what the city plow dragged along and dumped here.