Go Bottom Go Bottom

Pushing snow backward damages hitch

View my Photos
auerbach
Join Date: Sep 2007
Posts: 2168 West of Toronto
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-03          151051

Forgot where, but someone warned that rear-hitched attachments were meant to be pulled, not pushed, and pushing could pooch the hitch.

When I'm not moving snow I'm moving other heavy stuff, and use my blade a lot. I've modified the blade pivot to increase its maximum angle (so it's no wider than my track) and reinforced the weak point on the blade frame for when I'm pushing back with force. (Sorry if I'm not clear, but not important.)

For 35 years I've done more pushing than pulling. Has to do with manouvrability and keeping the wheels more level. With a weighted bucket and 4 chains, I sometimes push pretty hard.

Not arguing, just asking, what hitch damage am I risking?


Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
kwschumm
Join Date: Feb 2003
Posts: 5764 NW Oregon
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-03          151053

The hitch linkages are stronger in tension than compression. Here's a cheesy analogy. If you suspended a 10 lb weight from a toothpick it would probably hold the weight. If you dropped a 10 lb weight on top of an upright toothpick it would bend and snap. 3ph links are like that. They bend fairly easy under compression.

Although not applicable to a plow, pushing rearward with a pto driven implement can be real expensive if the shaft bottoms out. It can thrust the shaft right into the pto drive. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
candoarms
Join Date: Mar 2007
Posts: 1932 North Dakota
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-03          151054

Auerbach,

Kwschumm is correct. It's nearly impossible to stretch the steel bars of the 3-point hitch, when pulling -- but it's quite easy to bend them, when pushing.

You won't bend the lower 3-point hitch bars when pushing, unless you run into an immovable object, such as a parking curb.

Before any damage takes place, the tractor will have to come to a sudden and unexpected stop. This happens quite often when moving snow, where immovable objects are usually hidden.

Joel ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
auerbach
Join Date: Sep 2007
Posts: 2168 West of Toronto
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-03          151055

I take your point about the PTO shaft, thanks, but from my miniscule engineering knowledge, structures have more resistance in compression than tension. But tension, as in your example, self-balances whereas compression can cause skew. A thin pillar can take the weight of a tall building, but only if the pillar's fixed so it can't move. That's why I took the side play out of my hitch.

Even a rope is stronger in compression. Hang increasing weights on, say, a 1" twisted metal rope until it inevitably fails. Now encase it in a thick, vertical 1"-ID column, like a shell in a barrel. Force the top of rope down until it fails or collapses. It won't until it melts. What am I missing? ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
auerbach
Join Date: Sep 2007
Posts: 2168 West of Toronto
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-03          151056

Thanks, Joel. The metal hitch bars would be stronger in compression only if they couldn't move while being compressed, but they can, and so would bend from pushing before they'd snap from pulling. Sorry to be so slow. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
candoarms
Join Date: Mar 2007
Posts: 1932 North Dakota
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-03          151058

Auerbach,

I believe you're making this far more complicated than it really is.

The lower three-point hitch is constructed of flat bar steel. If you place one of those bars in a stretcher, you'll find that they'll survive under many tons of stretching pressure. But, if you were to place one of those steel bars on end, in a shop press, you'd easily be able to bend them......likely with less than a ton of pressure.

Those flat steel bars are designed for pulling.....such as when attached to a plow, cultivator, ripper, etc. They are marginally acceptable when pushing, so long as you don't strike an immovable object.

When you strike an immovable object with the end of a wide blade, or snowblower, the forces are multiplied.

Joel ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
hardwood
Join Date: Dec 2002
Posts: 3583 iowa
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2008-02-03          151059

Auerbach; I do agree with the others here about the resistance of a bar being many times greater in a pulling mode compared to compression. Now in the real world if you have been doing it that way for 35 years and haven't hurt anything yet then you obviously are a carefull operator who is comfortable pushing things around, so why change now? Enjoy doing it the way you do it. Frank. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
kwschumm
Join Date: Feb 2003
Posts: 5764 NW Oregon
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-03          151060

Steel can take an enormous compressive force, but it's maximized only when the compressive force is equalized throughout the material and lateral forces are eliminated. In practice, on a tractor that's nearly impossible to do. But the 3ph isn't made of glass. Frank is right, if you've been pushing for years and haven't bent or broke anything you're a careful operator doing it right. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
candoarms
Join Date: Mar 2007
Posts: 1932 North Dakota
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-03          151061

Auerbach,

Very few homeowners will ever damage a three-point hitch. The problem shows up pretty often with commercial tractors, where speed of operation is important, combined with an unfamiliar surrounding.

I've seen what happens to a three-point hitch after a tractor has struck a parking curb.....and it ain't pretty. One guy's seat looked like a recliner.....after he instantly came to a stop while backing at high speeds and hit a curb. The forces are incredibly high.

It's very important to wear a seatbelt when operating a tractor. Ask anyone who runs a skidsteer what happens when striking a curb while going forward. People have ended up lying on their backs on the ground, wondering what in the hell just happened to them. At first it's funny to hear the stories, until you realize what could have happened to them. There's a lot of lucky people who are still alive to share stories like these with the rest of us.

Joel ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
auerbach
Join Date: Sep 2007
Posts: 2168 West of Toronto
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-04          151078

Thanks guys -- appreciate the explanations and the cautions. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-04          151080

The other big item involved here, and one that has been skipped over, is the 3rd point, the upper link.

On almost every CUT it is nothing more than a two pieces of glorified angle iron with a few holes in it. Yet when it comes to 3pth damage I've seen more upper links bent and mounts destroyed than all the other stuff put together.

In a 'normal' situation for the 3pth, that of a tractive load against the lower links as if it were for instance pulling a rear blade, there is little if any force against the upper link, it is really only there to lift the implement and carry it clear of the ground.

If however you plow snow for instance in reverse, any shock loading caused by the plow catching on something will because of the shape of the rear blade) cause the plow to want to pivot (hitch up), this puts tremendous strain on the upper link.

Likewise, anything like a 'gin pole' or the increasingly popular 3pth mounted log skidder put stress on those bolts that is FAR in excess of anything it was designed to take.

As I said, I've seen more damage caused by this than all others put together. In the mild cases it was nothing more than a twisted bracket, or a few snapped bolts, I have however seen more than one instance where the entire piece of casting around the mounting boss broken right out of the rear differential housing. This is not a cheap repair, nor is it one a warranty will cover.


Best of luck.
....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
Chief
Join Date: Jul 2003
Posts: 4297 Southwest MiddleTennessee
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-04          151084

Auerbach,

Since your tractor is a Yanmar I am not certain what material they use for the axle and transmission housings but I do know that John Deere uses aluminum for these in their compact tractor line up. If you use these tractors to push snow or even push dirt with a box blade or other implement, be VERY careful.

I would STRONGLY advise against it as this can and has in the past caused the breakage of the cast aluminum axle housing rockshaft mount bracket on compact Deere tractors. Needless to say, this IS a VERY expensive and difficult repair.

You may want to run this by an experience Yanmar representative to find out if this is an issue with Yanmar tractors as well. Yanmar built the Deere 790, 990, and I believe the 4115 for Deere. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
hardwood
Join Date: Dec 2002
Posts: 3583 iowa
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2008-02-04          151091

Chief: I really don't want to start a debate on John Deere axle housings. Not saying it can't happen but the local dealership has never heard of one breaking in this aeria. As my Dad used to say there are folks who can break an anvil with a rubber hammer. Frank. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo



Pushing snow backward damages hitch

View my Photos
Chief
Join Date: Jul 2003
Posts: 4297 Southwest MiddleTennessee
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-02-04          151092

Frank, there is no debate. A few years back, John Deere updated and reinforced their axle housing castings because of an unacceptable failure rate. I have some pictures or the old and new updated housing along with pictures of a broken rockshaft mount. Just don't want to see anyone inadvertantly break something they don't realize may be a weak point under certain usages. ....

Reply to | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo


  Go Top Go Top

Share This
Share This







Member Login