rotary cutter deck cracking

[duane]

Re: mystery solved!

Ken,

I agree with you. I don't think it has to do with the float position or lack thereof. It's the high push point from the PT to the deck. A better explanation is like pushing a grocery cart. It goes along well on a flat hard surface. Once the going gets tough (ie: imagine pushing a grocery cart through beach sand), the overturning load gets high. With the bushhog, when the going gets tough (pushing through heavy brush etc), the PT pushes to meet this resistance. The overturning load will heavily load the front castors, and deck structure in between the push point and the castors.

It looks like the welder understood the load points and placed the stiffners in the right locations. Let us know how this holds up after time.

 

[MossRoad]

Re: mystery solved!

<font color="blue">how do you post multiple pictures and how do you put pictures in with your text? I have noticed some TBNer's doing that. I would appreciate whatever information on posting pictures that you can give me.</font>

I don't know how you could post multiple pictures as attachments in one post. You could use the IMAGE command multiple times in a post, but the pictures would have to be posted somewhere first.

Here's an example of the image command:

If you right click on the image and go to properties, you can see that the image does not live on TBN, but on my personal web site.

The IMAGE command can be used to put a picture in with your text so that it appears without the reader having to open an attachment. The IMAGE command refers to the URL of a picture that has already been posted somewhere. So, you could post a message with an attachment, then go back, click on the attachment. When it comes up, copy the URL of the attachment and go back to your original message, edit it, and insert the IMAGE command, refferencing the URL of the attachment. The next time someone reads the post, the image will appear inline with the text.

The downside to inline images is that everybody that clicks on your message is forced to look at the image. If someone has a dial up connection(like me /forums/images/graemlins/wink.gif) and there are several images in a thread, they all will be forced down my pipe to the internet, thus choking it out. One nice feature of TBN is that the text loads first in the posts, so I can read the post while the picture is still downloading. A lot of web designers don't go to that trouble for the user(or they don't even know about it).

Hope that made sense /forums/images/graemlins/crazy.gif

 

[johara1]

Re: mystery solved!

anytime you have a loader (a pt is set up like one)and you put the thing in float it will ALWAYS want to climb up the arms with any kind of resistance.so if you put the bucket on and put in float the front wheels come off the ground,same with mower it meets resistance the wheel or wheels come off the ground. side ways on a hill the upper wheel comes the ground,this puts pressure down on the deck. CRACK, this is a poor set up at least poorly engineered. a brace off the upright on each side down to the caster may help and make it more rigid.

 

[MossRoad]

Re: mystery solved!

<font color="blue"> if you put the bucket on and put in float the front wheels come off the ground,same with mower it meets resistance the wheel or wheels come off the ground. </font>

Well, I've seen that with the bucket many times. I suppose the mower has to do the same thing, but to a much less extent because of the wheels VS the bucket just skidding along the ground. I've never seen the mower come up due to resistance with the ground. I guess if you got into thick enough stuff or the front wheels got up agains some large sapplings or something, that could happen. I think someone mentioned that is why they use draft control on the larger units; to protect the implements.

 

[johara1]

Re: mystery solved!

mr, that the condition that everbody talks about that cut the side of a hill.they have to take it out of float to keep the up hill side wheel down. also when you go into a hill from the level it raise the back wheels of the deck up.if you go up a hill it will start to climb up and the front wheel spin out.if you never had this happen your on flat land, it's a diff. ballgame here in the hills. /forums/images/graemlins/smirk.gif

 

[Kaon99]

Re: mystery solved!

I have looked carefully at my rotary cutter and thought about Duane's analysis. I think he is exactly right about the bending/cracking problem. The high connect point provides a powerful lever arm for bending the deck when you try to push the rotary cutter into saplings, bushes, etc. Terry at Power Trac commented to me that the rotary cutter deck does not carry much weight and that is true. However, if you multiply a typical pushing force (mowing saplings, etc.) times the distance from the attach plate connect point to the connect point on the deck, you will find that the deck has a large bending torque applied to it. To make matters worse pt has the connection to the deck near the center where the deck is not as stiff as on the edges. (The finish mower has a shorter lever arm and has the connections to the deck near the edges where the deck is stiffer. ) A possible fix by Power Trac would be to lower the height of the attach plate connection and move the connections on the deck itself out near the edges. For those of us with the existing 4 ft rotary cutter, we either have to be very careful about pushing into saplings, brush, etc., or else add some kind of reinforcement to the deck such as angle iron bracing. I appreciate all the thought and comments from the pt forum folks on this problem. I will let you know how my "ruggedized" rotary cutter holds up. Ken in Mississippi

 

[johara1]

Re: mystery solved!

i think a brace from each side of the bracket at the highest point on each side where you attach to. down to the square tubing on the front caster wheels would stop the flex.

 

[duane]

Re: mystery solved!

Ken,

I want to thank you for bringing this problem to the forum. One of the biggest values (besides having fun) is identifying a problem and then providing a solution. You did both.

After seeing your cracks, I ran some numbers. The maximum moment created in the deck from the maximum push capability and the high attachment point is close to the allowable for the material in a static case. Add the dynamics of impact and operation, well you demonstrated what happens. My quess is that the flexing cracked your side skirt, and once you lost this vertical stiffner, your deck bent. The front to back angles add alot of stiffness (as well as Johara1s braces). If you are using your machine in heavy stuff on rough ground, it would be wise to add stiffness, or frequently inspect the side skirts for cracking.

This is a great thread.

I also wanted to add, that I have pored over every specification and detail I could get my hands on for the PT 400 series. I believe that the product is well designed. If I had to do it all over again, my decision would be a no brainer, a Power Trac for me.

Duane