Whats wrong with this picture

[woodlandfarms]

So, this will be the 4th time I have had this straightened. I now realize 2 things are happening. If I hit a buried stump with the mower, this bad boy takes the brunt of the impact. 65HP, 4000LBs coming to a dead stop. Also, it seems that my mower impacts with it. I am working out that problem / solution at the moment.

So, I took some measurements. JJ, this will be right up your alley.

It is 1 - 3/4" bore, 20" Contracted, 34" extended (14" of travel). Rod is 1" Diameter.

I would love some beefier suggestions. this is for the dump mechanism so speed is somewhat important.

Found this at Surplus... thoughts? https://www.surpluscenter.com/item.asp?UID=2009112517312914&item=9-7709-14&catname=hydraulic

 

[Gravy]

Just a few observations:

1) That rod looks awfully long and skinny. I'm not surprised it bent. It might hold up if you had it custom made from unobtanium.

2) According to stuff I've read, strength increases 1:1 with cross section, (somebody correct me if I'm wrong) but stiffness increases by the square of the section. I think you need stiffness first, followed by strength. Going to 1-1/2" will likely let you find the next weakest link.

3) I can't remember all of that "pie are equal to .342516789 of chocolate cake" stuff, but I think you are right that speed is important. 2-1/4" sounds awfully slow.


Good luck with the juggling act. Get it right, take it on the road, and you'll be a STAR!

 

[SpringHollow]

unobtanium - Gravy, you really crack me up

Carl, that one has the wrong ends on it.

Ken

 

[woodlandfarms]

Hey Ken

I am not sure in this application the ends matter too much. Any reason why you think it would?

 

[Old Paths]

Pie are square, PSHAW...
Cake are square, pie are round

 

[SpringHollow]

Carl, you are probably right. And that shaft does look quite small in that picture!

Ken

 

[toy]

Woodlandfarms, I was thinking about what you are saying and it seems to me that if you was mowing at a pretty fast clip and hit something that stopped you dead in your tracks that the main impact would be absorbed by the loader arms first and then onto the rollover and then on to the cylinder. It would seem to me that the impact to the cylinder would be a straight in shot and not at an angle. Now if the cylinder rod was already bent then that could maybe explain some of it. You said that the mower deck was hitting that jack, that seems to me that that would be a more likely cause of the bending jack rod. I noticed on mine a while back that when I lifted up the mower deck or brush hog, don't remember which , but anyway the back edge of the deck caught on the cylinder where the rod comes out of the barrel and the possibility of bending the rod came to mind, so I try to watch out for that. If you could limit the forward tilt of the mower deck that might solve the problem. Also a while back some mentioned reinforcing between the two arms where the jack attaches but if the jack hit that reinforcement before it bottomed out that could bend the rod also, just in case you had your machine done that way. Just a thought.

 

[J_J]

Carl,

Yep, I do believe it is bent, but there is hope.

Did you say this has happened before and you had the shaft straightened? Not a good thing.

What happened, would be expected if you ran into something to fast. I believe you said before, the rod that connects to the bucket has broken also. The impact that you are experiencing, will shove those forces backward until it finds the weakest part, and in this case, it was the cylinder rod. A thicker rod would help, but the force will still go to the next weakest part. About the only way to get around something like that is to over engineer the front setup. You can probably surmise from the result what happened. Forces greater than the cylinder designed factor were at play here. The only logical thing here is to install a stronger cylinder. As long as there is no side play, tube end cylinders might work. Might go to a 3 in bore with a 1.5 or 1.75 in shaft.

https://www.surpluscenter.com/item.asp?UID=2009112607274769&item=9-7712-14&catname=hydraulic

http://baileynet.com/index.php?id=14&productcategory=1000001

Baileynet.com can make you any kind of cyl you want.

 

[woodlandfarms]

Thanks for the info JJ. Here is my question, probably to you as you are the HD genius.

If I go with one of these larger cylinders, what happens to my speed of tilt and dump (I doubt I use the full speed ever anyway, but I would hate for it to be log splitter slow at high speed).

How do you look at a cylinder and know how quick it is going to respond?

I am also mulling over replacing my lift cylinders (probably won't due to financial restrictions).

Yes, this has been bent a few times, and the rollover has broken a lot as well. I have not hit anything at high speed, but at any speed there is resistance.

Also, I made a mod to my mower that locked the mower to the cross bar. It worked great for lifting and crushing black berries (I could keep the mower tilted away from the cab) but as I now know it put some stress on the front of the mower bar and probably on my rollover as well.

Also, I have a new rollover (Peice of 1" steel) that I will install this spring.

 

[J_J]

Carl,

Using 5 GPM as a ref,

1.75 bore, 1 in shaft, extend time is 2.39 sec

3-0 bore, 1.75 in shaft, extend time is 5.18 sec 21,000 lbs compares to 7,216 lbs, 3 times stronger than what you are using now.

A regen valve would double the extend time.

I have mentioned this before, about the geometry on the rollover link. For equal force, the rigging should look like a square. You have max force when the cylinder is at right angles to the push/pull plane.

 

[woodlandfarms]

Hey JJ

Thanks for the info. Could you give me an idea of where you got this formula? I would love to make some decisions if I were to upgrade the lift cylinders a bit.

I guess it comes to mechanical force and angles, but I find it weird that PT uses two lift cylinders and only one tilt...

 

[J_J]

Carl,

You can take a smaller cylinder and use it more effectively by applying the forces to your advantage. Say your lift cyl have a potential force 8000 lbs of force on the lift arms. Now, 16,000 of force applied at an angle reduces the total lift force, and if the same cylinder is used for curl/tilt, if applied correctly it could have more force applied, by adding in the mechanical advantage. The lever principle would apply here.

A 2 in cyl, 1 in bore pushing at 90 degrees, at 3000 psi will push with a force of 9425 lbs

Two cyl giving a total force of 18,850 lbs

A 2 in cyl, pushing " " " " " 30 degrees, will push with a force of " " " 4712 lbs

Same two cyl would now push 9424 lbs

That means that the two cyl are now equal to the one cyl pushing straight on.

The fill in the numbers hydraulic tables can be found at Surplus Hydraulics.

https://www.surpluscenter.com/techhelp.asp?UID=2009112700191587&catname=hydraulic

Then select Hydraulics, select tech help, select force and speed. just fill in the numbers.

 

[catsco]

Side note for those not familiar with special engineering alloys; unobtanium (UoB) is infinitely strong, weightless, and just under $1.00 per ton fabricated.

Only issue is wait time is 845 years minimum without a time machine.

:->

 

[J_J]

This is just a test. Skyneptity Drive unit.

I noticed that some of the TBN post would appear in an Internet search, and was curious how and why.

 

[wasabi]

In response to JJ's test: it worked...