Hydraulics help, loader schematic, information

[candubobby]

unless you have the exact measurement of the pivot to cylinder distance, or you have a cad to work it out, it is almost impossible to get it right by trial and error. Moving the pivot of the cylinder by an inch and affect your curl by 10-15 degrees depending on the leverage you are using.
Unless you have done this before, maybe you should order a plan by sending in a cheque. Any changes you have to make will inevitably costs you a lot more than that. The price of hydraulic fittings are not cheap and you have to be pretty exact when you are plumbing it. I do not know how much it costs for the plans, but I am sure it's worth it.
I design my SKID STEER ( see junkyard skid steer ) with a cad, and even then, have to make a couple of changes that costs me a lot of time. Fortunately, I have all the stuff lying around and does not costs me a great deal of money.

 

[Mith]

Im using ProDesktop, I can get it pretty close on there, the final bit is with the rams on tack in the place I worked out with ProDesktop and try, then retack, weld when right. All this before it even takes a look at any hose.
When I was making the linkage for the plough i made pieces out of wood and cut them before i used metal to get the right lengths for parts, I dont see why i cant do a similar thing to get the right spaces for the rams.
I dont see how it is difficult to move a piviot pin, just grind and reweld the piviot where you want it.
Why do I need to plumb it it before ive tested it my moving it by hand (engine hoist) with the cylinders just in place?
Im not just blundering in blind, I am gunna have some plans on the computer.
The plans would probably about $100 after shipping.

Sorry if this appears a bit irritable, I am most certainly not annoyed, I thank you for your advice.

I attached a pic of the proposed bucket, I havent started designing the frame yet becuase im deciding on the steel to use. Sorry, the dimentions are inside out because of the way I drew it.
Im really not in a rush, ive gotta have something to do over winter afterall

Thanks very much for you insgiht, please advise me on anything ive missed or not got right, I really appretiate the comments, and trust me, I am taking them on board.
Cheers

 

[candubobby]

hydraulic cylinders are almost impossible to extend and contract ( if they are in good working conditions ) at least not 2 inches one that can take 2-3000 PSI. Because of the arm and the curl sort of interact and change the angles, you either have to model it with wood and some sort of extension contraptions or use a cad to simulate the action. When your arm moves up and down, it changes the angles of the curl too. Also the curl / arm mounting point for the cylinder is quite critical ( i.e. have enough clearance. you want to get at least 70 to 80 degrees of curl angles to allow for easy dumping of load when the bucket is raised. Of course all these depends on the max lift you try to achieve and your center point of gravity and how much your tractor weights. I did all the calculations and simulations but forgot the extensions of the hydraulic fittins when the arm is fully raised and have to spend 3 hours grinding away to make it work. ( the cylinders port are slight raised and I did not account for that ).
Of course, my skid is made of junk metals and have to deal with a lot of weird angles and curves. using straight pieces of material will definitely helps a little, NOT A LOT.

Anyway, good luck on the project, like you said, do a lot of tagging before putting the final welds on. I am sure you will run into a couple of surprises.

 

[candubobby]

Sorry, I am not trying to get you upset or imply that you are not capable, just pointing out a few pitfall that a project like this inevitably gets into.

I know I ran into a few problems no matter how careful I was in the design phase.

I did not see the attached bucket you are talking about. Maybe just lost in the post somewhere.

 

[JerryG]

Jim,
I am sure that you can do it, just take your time and measure twice. I am sure someone told Henry Ford that he couldn't do it when he was casting his first engine on the dirt floor of his garage.

 

[Nat]

This may not be revelvant, but in building several dump beds for trucks and trailers I always used my air compressor and a couple spare fittings to test/determin final location of cyl placement. A note of caution when using compressed air the cyl can suddenly extend and go all the way, not like when using hydralic power, so be real careful if you chose to try it.
HTH, latter, Nat

 

[Mith]

Sorry forgot the picutre. Ill put it on this one.

I thought you could push the ram in and out by hand when theyre not connected up, Im pretty sure ive seen it done.
For example for the curl, can i not raise the loader up all the way, fix the curl cylinder to the bucket push it out all the way, tilt the bucket to the desired maximum tip see where the frame end of the cylinder comes to and weld the piviot there. That is the way I figured I would do it.

I havent really thought about cylinders yet, I think working out the length ect will be a function on the CAD. Can I not mark 2 piviot points in pencil, measure with the boom lowered and with it raised. The difference between them would be the extension I need on the ram, then order a ram with that extension?

Im thinking on my feet here.

Trust me, im grateful for your comments, gives me things to think about that I hadnt thougth of before. there are going to be problems even if you follow plans but isnt the whole point being able to overcome the problems.

 

[candubobby]

if they are new and high pressure type, it is very difficult to pull or push ( i.e. impossible ). If you can push them back and forth, the seal is almost gone.
If you are to test it with air, make sure the air is WELL FILTERED and squirt lots of oil in the cylinder before you do it.
If you connect it up to the curl and lift arm, the chances are that the air does not have enough power to lift it, because of the extreme extension or contraction of the cylinder, it is at a pretty steep angle ( you will have to go to the sine/cosine table to work out how many PSI you will need, it will be more than the 125 PSI you are going to get from the compressor. There is some danger in damaging the cylinder also from using air for testing, this is according to the technician that I spoke to that specialized in Seal Selection, it's similar to use oil of too low a viscosity in hydrualics, it will demage the seal, not to mention the amount of comtaminates that can enter the system.
You are absolutely correct in working out all the stuff on the cad first, and if it does not have one that can animate the action of the boom, you can do it with two arcs that is the min and max length of the cylinder and plot the pivots that way.
However, you should look into what is available at what costs in your parts of the woods and get the most economical one, usually the ones on sell or extra stock and cancelled orders from other people, it will save you hundreds of dollars. You can evern try EBAY, but the quality is not assured.
Before you do all that, you should determined the max lift, max weight, that will dicatate pretty well your pivot points for your lift arm, once that is done, just use the two arcs method that I mentioned above and the pivot point will be determined.
For the curl, once you determined the attachment angle, the rest will just follows, making sure that you have enough curl to dump the load when it is raised. It's definitely worth while to get a joy stick, and putting a throttle control ( semi adjustable ) on the curl will make your work 10 times faster.
That way, you can make the raise and curl sort of sychronized, Not being able to raised and curl at the same time with the proper rate with one hand will probably drive you crazy after a while.
Hope this helps, just don't do what I did and did not account for the connector height when the arm is full raised.

Bob

 

[candubobby]

Just had a look at your bucket design. I think it will be wise to copy an existing bobcat one with three sided, it's easier to fabricate and attached, and having a steeper rake at the rear allows your bucket to be closer to the tracter to get the up curl angle you want, plus the added savings in materials and better strength. By having a almost vertical back, you will have to attached fairly high on a pivot point, meaning a much costlier cylinder and takes a lot longer to go thru the curl. You need a pretty fast curl sweep if you use it for moving dirt and clay to dump it completely, otherwise, a lot of it will stay on the bucket.
You will get more volume with your design, but I think if you are to use it in a small tractor, you will run out of lifting power way before you will run out of volume.
Depending on how many HP you have available to you, GPM is not a big thing, Pressure is where it is at. You must first determine the max weight, angles of pivots and leverage, then determine the min PSI that you need. Your GPM will be govern by the HP available.
The formula is HP = GPM x PSI / ( 1300 ) for a gear pump
Pump displacement in Cu In. = GPM x 231 / ( pump RPM )
Once you have all these and you have the diameter of the cylinder and length, you can then determine whether it is acceptable to you in terms of how long it takes to go thru the entire lift curl cycle.
You need a lot less power to curl than lift usually, and make sure you use the push side to lift or curl up if you are at the limit of the hydraulics, depending on the rod diameter, it is usually much stronger on the push side.
Force = piston area x PSI on push but must minus rod area for pull.
Time to entend is = piston area x stoke x .26 / (GPM)

Hope this information is useful and
ALL THESE ARE MERELY SUGGESTIONS.

good luck.

Bob

 

[Mith]

I dont get what you mean with the 3 sided bucket, the bucket looks similar in design to most CUT buckets. Can you draw a digram or find a picture if possible.

The valve I plan on using has regen dump, as a result it should dump really fast. It also has float.
If you take a look on www.machinebuilders.net and hydraulics 101 at the bottom there are some great charts that you can work out all sorts of things. Really useful (thanks Mr Machinebuilders /forums/images/graemlins/wink.gif)

I can think of any way that I could have a ram so that the push side curls up the bucket. Again drawing or diagram would be great!

Thanks, very useful information and great suggestions, its great that you can learn from more knowledgable people, thanks for the forum! /forums/images/graemlins/cool.gif /forums/images/graemlins/laugh.gif