Cylinder for post knocker

[Keif]

I made a vector style post knocker for my Takeuchi using a cylinder I had on hand. It appears that the large volume of oil in the 24" cyl is preventing the weight from free falling. That is the only difference I can see from what I made and the original.
#1 Would you agree with this assessment?
#2 Do you have a link or any specs for a cyl that will work?
#3 Any other suggestions?

Here is a picture of the cylinder I tried using.

I've tried every type of hose configuration and breaker valve(thanks @V8Druid !) open/closed with no luck.

 

[Smiffy]

I made a vector style post knocker for my Takeuchi using a cylinder I had on hand. It appears that the large volume of oil in the 24" cyl is preventing the weight from free falling. That is the only difference I can see from what I made and the original.
#1 Would you agree with this assessment?
#2 Do you have a link or any specs for a cyl that will work?
#3 Any other suggestions?

Here is a picture of the cylinder I tried using.View attachment 22156
I've tried every type of hose configuration and breaker valve(thanks @V8Druid !) open/closed with no luck.

It appears you have a hose plumbed in both ends of the ram
Post knockers only use one end and the other end is just vented
The vacuum trough the plumbing will slow the ram as much as lack of return flow from the other end

 

[Storrsy]

Yes as said, knocker only needs to be single acting. Ie it pushes the weight up the mast and the weight forces the fluid down the same hose as it’s released/weight drops.

put some pics up of your knocker will be keen to see it!

 

[V8Druid]

as above .... single acting only @Keif ....... put a free flowing breather in the top port - do not want any oil in there ... the dropping weight will force the oil from under the piston back into tank through the spool and plumb the second way to tank as we discussed in PMs Boyo -- you're literally dumping the second way direct to tank which opens up the return route for the first way via the spool architecture.

 

[Keif]

It appears you have a hose plumbed in both ends of the ram
Post knockers only use one end and the other end is just vented
The vacuum trough the plumbing will slow the ram as much as lack of return flow from the other end.

It just like that for the picture because I was trying every way I could. I tired it with the lower hose disconnected as well.

 

[Keif]

Yes as said, knocker only needs to be single acting. Ie it pushes the weight up the mast and the weight forces the fluid down the same hose as it’s released/weight drops.

put some pics up of your knocker will be keen to see it!

For better or worse I made mine with he rope and double pulley set up. The cylinder retracts to raise the weight and extends to drop it. Ill load a pic of my creation later, my shop is so tight I can't get far enough away to get a full picture.

 

[Keif]

as above .... single acting only @Keif ....... put a free flowing breather in the top port - do not want any oil in there ... the dropping weight will force the oil from under the piston back into tank through the spool and plumb the second way to tank as we discussed in PMs Boyo -- you're literally dumping the second way direct to tank which opens up the return route for the first way via the spool architecture.

I'm what ya call smart enough to get into trouble but not smart enough to get out of it........ the valving appears to be working correctly. The solinoid is powering up and if I close that side of the circuit on dipper arm I can press the pedal with out it dead heading.

As an experiment I raised the weight and disconnected then 1/2 dump line before the diverter valve. A crap load of fluid came shooting out but the weight still didn't freefall. It filled up a 24oz metal coffee tin before I shut it off and didn't even come near to fully extending the cyl. That's what makes me think the volume of fluid in the cylinder is the problem.

 

[Jimbo69]

How about setting it up something like this with a smaller ram.

 

[Keif]

For better or worse I made mine with he rope and double pulley set up. The cylinder retracts to raise the weight and extends to drop it.

How about setting it up something like this with a smaller ram.
View attachment 22166

That is a good idea, but I'm really hoping to get what I made working. That would be alot if changes.

This is the style I made.

There are videos of it running on a Tb016 also.

@doobin you have any ideas? I read a thread on another forum and I think you said the cyl should be so small it will work without even having a dump to tank valve? Maybe I read it wrong.

 

[Storrsy]

Here’s mine on my tb216, weight drops very well

 

[Jimbo69]

That is a good idea, but I'm really hoping to get what I made working. That would be alot if changes.

This is the style I made.

There are videos of it running on a Tb016 also.

@doobin you have any ideas? I read a thread on another forum and I think you said the cyl should be so small it will work without even having a dump to tank valve? Maybe I read it wrong.

Is that your one or one the same? It looks like the ram is double acting, going back up quicker than the weight drops initially. Do you have a smaller diameter ram you could try with, set up the same as you have but the smaller diameter should extend quicker and work more like the video? Or am I barking up the wrong tree

 

[Keif]

@Jimbo69 This is my creation the cyl is removed. I haven't don't the final welds to finish it off because I wanted to see it drop/check clearances first.

 

[Keif]

Here’s mine on my tb216, weight drops very well

You will be my hero if you can give me dimensions, specs or anything to help my local hydraulic dudes get me the correct one. Please describe the hose/valving setup also. Talk to me like I'm a dummy. Lol.

 

[V8Druid]

you mentioned diverter valve above @Keif ...... just how have you got this set up ?????????????
I see you're pulling the cord with the return stroke of the ram, but where/how are you oiling it ??

 

[Storrsy]

You will be my hero if you can give me dimensions, specs or anything to help my local hydraulic dudes get me the correct one. Please describe the hose/valving setup also. Talk to me like I'm a dummy. Lol.

Il measure the ram when I’m in the yard. When you say 24” ram- I take it you mean 24” extension of the ram, what diameter is the rod?
Mine is (cough) pretty small- but effective! How heavy is the hammer weight and how far does the hammer need to travel up the mast?
Mine is same as vectors design- i disliked that the vector one hung offset as didn’t like the twisting motion it applied to boom- so got a company to fabricate to my specs with knocker direct in line with the digger arm.

 

[Storrsy]

You’ve switched the digger itself to single acting mode I take it!?

 

[Keif]

You’ve switched the digger itself to single acting mode I take it!?

I opened the hammer valve and closed the valve on the right side of boom. Anything else I need to do.

 

[T whiting]

It sounds like your ram is far too big a tiny hydraulic ram is far stronger than you are one with a rod the size of your little finger will lift you you could try adding more falls of rope so less movement on the ram gives more movement for the weight.

It does give you more chance of a tangle but it would give you a proof of concept

I'd say the hammer valve would want to be set to free return (hammer mode) I can't see the tap on the quick for that's not connected making any diffrence

 

[Keif]

you mentioned diverter valve above @Keif ...... just how have you got this set up ?????????????
I see you're pulling the cord with the return stroke of the ram, but where/how are you oiling it ??

I have the left aux line hooked up to the top port on the cyl, no lines and open ports on the bottom of cyl. I replaced the elbow that connects the a6 hose to the valve body with a tee. New tee end goes to 1/2 hose to 30gpm diverter valve. 12v to solinoid opens it and dumps into tank return. Setup exactly like Tak parts diagram, just uses elec instead of manual.

Press the left side of pedal to apply force to retract cyl and raise the weight.

 

[GazCro]

Should be a single acting ram of the minimum size needed to do the job to keep oil volume as low as possible.