Is there an ME in the house?

This a hydraulic cylinder application question. The mid mount cylinder on my JD4410 that raises and lowers the five foot deck went south to the tune of over $300 to replace. Me not wanting to part with said cash went hunting on line and found addresses, one of which was fairly close .Long story long I'm back home with a 1" cyl  bore 6" stroke hyd cylinder for right at $100...........yea I think, bolts right in no prob, except it wont hold the 300# mower deck in the up position whether running or not(clicks and pops and drops). The original JD cyl had a reservoir so to speak(approx 3" in dia) for hold time? Or is this new cylinder to me in need of a reseal.....or some sort of holding tank reservoir? FYI space is at a premium up under this tractor where all this mess resides. Help.

759NRNG said:

Is there an ME in the house?

It seems like YOU are probably in the garage, and not in the house...Unless you consider the garage a part of your house. 

Seriously needing input from a Mechanical Engineer versed in hydraulic dynamics /applications...and no i'm not one nor did I sleep in a holdiayinnexpress...

Hate to say it but it sounds like you don't have a big enough actuator. Or to compensate for that enough pressure. Won't hold the weight. Not an ME but work with hydraulics a little. Try this calculator. Hydraulic Calculator to figure out what the old one was and how the one you bought compares.

What size is the original cylinder ?     Failure to hold indicates leakage , either in the cylinder or the valve.

I am not a ME but I did sleep at Holiday Express once.

I read ME as Medical Examiner. I was expecting a very different sort of thread.

In reply to iceracer :

The original cylinder was an odd arrangement......three inches in diameter(reservoir?) with the two hose connections, a single rod on the piston side with a 'U' bracket on the reservoir body for attachment  up under the tractor. I'll use wlkelley3 calculator to see how far off I am.....and yes this new cylinder(custom made) had been sitting on a shelf in the warehouse.

So you are trying to use a cylinder not designed/engineered for this application.  Now that it's not working, you're trying to troubleshoot it while knowing very little about either cylinder.

I think you might be looking more for agricultural field-repair than engineering when it comes to implementing and troubleshooting such solutions.  My official recommendation as an ME would be to simply use parts designed/engineered for this application.

If I read this correctly, you have a three inch bore double acting ram with a one inch shaft, and you have replaced it with a one inch bore cylinder.  That won't work, since you are undersized by pi or so.

When I worked for JD we would just reseal the cylinder.

Its all about the PSI - pressure (Pounds) and area (SI - Square Inch).    You had a cylinder of 3" diameter = ~7 Square Inches and replaced it with a 1" diameter ( ~0.8 Square Inches).

If your pressure is 100 psi the old cylinder could lift 700 pounds (100 * 7) and the new one can only lift 80 pounds (100 x 0.8)

You need to find a cylinder the same diameter and stroke.

To all that have responded thank you for your input . In closing I will  say this, the reason for the 'smaller cyl' was due to financial constraints.....yes it does lift the 5 foot mower deck, quite rapidly I might add, it just doesn't hold it in the up position...I'll live with it. Also the original cyl in JD's infinite wisdom is non rebuildable ($300+).

02Pilot said:

I read ME as Medical Examiner. I was expecting a very different sort of thread.

This!!!!!

In reply to dean1484 :

I didn't know there was a CSI/GRM forum......where'sit????

A couple of pictures of old and new cylinders would be a big help. Your descriptions of parts are confusing to someone who knows a lot about hydraulics.

It sounds like you replaced a 3" double acting cylinder with a 1" cylinder. Holding it up has nothing to do with size of the cylinder. It has to do with the load holding capability of the system, and whatever you may have changed when you switched the two. Is the 1" cylinder double acting? A little more info would go a long way.

Here is a pic of what I think the original cylinder is:

https://www.ebay.com/itm/John-Deere-4200-4300-4400-Mower-Deck-Hydraulic-Cylinder-AM124898/302508503726?hash=item466ee972ae:g:SkAAAOSw8GtZPwjm

Ebay link to Cylinder

In reply to 759NRNG :

As an ME for a hydraulics manufacturer, I also recommend buying the part as designed.

As a GRM, I recommend finding someone to rebuild it. They are always rebuildable, you just have to find the right person.

If the cylinder looks like the one above its just a welded cylinder that is considered a "throwaway" by JD. Any cylinder repair shop local to you can part off the base plate, reseal it and weld it back together. Whether they will do it for what you can afford is a different situation.

I came here as an ME, but Master Electrician is not the droid you're looking for.  Move along.

Curtis your presence is always welcome whether you are able to contribute in a meaningful manner or not.....thank you .....oh we need to talk master panels some time.....

D2W the JD part is POS for $300 IMHO .....that's why i went to the known HYD purveyors in the Houston Texas area.......talkin junk to these cats revealed to me that the little cylinder that could would be sufficient for my application. OK maybe not.....I'm more inclined to R&R my cylinder than the JD.......thanks Y'all

759NRNG said:

Curtis your presence is always welcome whether you are able to contribute in a meaningful manner or not.....thank you .....oh we need to talk master panels some time..... 

Thanks!  If you want dramatic theatrical lighting for photographing your tractor, I'm your guy 

In reply to 02Pilot :

I was thinking Dr Quincy 

Ok, lets get back on subject.  What are the specs of the original cylinder, online I can only find images.  That said, depending on the desired stroke I've seen other aftermarket welded cylinders for JD out there

example

https://www.ebay.com/itm/Snow-Plow-Lift-Cylinder-Fits-John-Deere-317-318-Hydraulic-Blade-AM31362/192266436752?epid=2158774394&hash=item2cc3f90090:g:l~MAAOSwf7dZg2u5:sc:UPSGround!42104!US!-1

If the cylinder can lift the deck then I see three possible issues.

1. Internal leakage in the cylinder.  Probably not since it can lift the deck quickly.

2. The up/down valve is leaking internally when released.  I assume it has a closed center that should hold the pressure in the line from holding up the deck.  That pressure is much higher given the smaller surface area of the new smaller cylinder.  It may be enough to cause leakage that didn't happen with the original larger cylinder.

3.  There may be a check valve in the control valve.  The higher pressure in the line to the cylinder is overcoming the check valve.  That may be adjustable or replaceable with a higher pressure valve.

Green VW wow thanks for the digestible insight to what i'm experiencing . When I swapped out cylinders there were restriction orifice disk thingies in the lines to and from.....which i subsequently left in place .....possibly my prob???? Would these ro's cause the popping clicking that i hear in the up position at idle (1000rpm)?