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View Full Version : 20,000gvw 8x18 dump trailer motor too small?


Ramairfreak98ss
04-02-2010, 01:02 AM
we have a 2007 7x14' , 14k dump trailer, its "small" in comparison to the other trailer we got last year. Its a 8wide by 18' long by 4ft tall and a 20,000lb rating.

The pump/hydro resevior is the SAME on both trailers.

Now the 14k trailer, has dual hydraulic cylinders that lift up, it takes roughly 30 seconds to go from full down to full tilt with 2 pistons.

The 20k trailer has ONE monster RUGBY 10 ton scissor lift, it moves SLOW, i mean if i ever got it to full height empty, it would easily chew up close to 2 minutes or longer.

Not only is it obscenely slow, probably because of gpm of the same motor, but the fluid empties completely from the 2gallon small tank when its only half up in the air... i added THREE quarts to it today and got it to go up another 1/4 of the way, but still not ALL the way up. When i put it back down, the tank overflowed after going down half way :/

So i pumped OUT the same 3 quarts and it went all the way down, again filling the tank. So do they MAKE larger tanks like a 4 gallon and larger motors for these? Trailer already had upgraded to 2 batteries and getting a couple monster marine batteries would fit somewhere underneath the trailer for the future.

Im not an electronic hydraulic pump expert, please give me your opinions of what to do... trailer also hardly tips half full of mulch.

I think the rugby unit is their TB-16.. its a 6x19" bore cylinder shaft for an 18' trailer... actually mine looks just like the one pictured on their page 1 of their PDF brochure http://www.rugbymfg.com/rugby-pdf/Trailer%20Hoist.pdf only has the rugby logo on it

Gravel Rat
04-02-2010, 01:38 AM
For what you have it is time to upgrade to a gas motor with a small pump on it I know its not something you want to hear but it is the best solution for the problem you have.

I have a 12volt hydraulic pump set up on my F-450 it is slow as molassis I had to put a 4 gallon tank on mine I have a 3 stage post hoist something like you see on a big dump truck.

Williams Hydraulics makes a pump tank combination just what you need it comes with all the valves you would mount it on the tounge of the trailer. You could power it with a small gas motor and do you think I could find it on the net.

zabmasonry
04-02-2010, 04:40 PM
speed aside, this seems like a manufacturer issue to me. speed aside, they should have sized the tank to lift the trailer all the way. Two Gallons seems massively undersized, My calcs suggest it needs more like a 12 gallon tank ( could it be 2 cubic feet?. One thought I have is that the piston is air locked, and thus may be not working right, although that doesn't seem likely. If the tank is undersized, I would make a stink about it.

CLARK LAWN
04-02-2010, 10:55 PM
what are the sizes of the rams on both trailers? they could have the same surface area between the two just the bigger one is slower as it more area to fill. if you just bought this last year and it never worked since day one why didnt you take it bake to the dealer?

meador56
04-04-2010, 08:54 PM
hoist cylinders on electric pump are single action and use the cylinder to store oil.

CLARK LAWN
04-04-2010, 09:45 PM
hoist cylinders on electric pump are single action and use the cylinder to store oil.

uuhhhh noooo

zabmasonry
04-07-2010, 10:56 AM
the more i think about this, the more I think that you have an airlocked cylinder. I think that the side of the cylinder that is acting as a reservoir has quite a bit of air in it. I think that what I would do is disconnect that from the system (set it up to drain into a bucket), periodically filling the tank, raise it all the way, hopefully ending the tank just about empty. Then reconnect the reservoir side of the system and hopefully it should go all the way down and work correctly.

GravelyNut
04-09-2010, 09:18 PM
the more i think about this, the more I think that you have an airlocked cylinder. I think that the side of the cylinder that is acting as a reservoir has quite a bit of air in it. I think that what I would do is disconnect that from the system (set it up to drain into a bucket), periodically filling the tank, raise it all the way, hopefully ending the tank just about empty. Then reconnect the reservoir side of the system and hopefully it should go all the way down and work correctly.Or something is plumbed wrong. With a double ended cylinder that uses only one end, the shaft end should serve as extra storage for oil. As you say, it may be airbound and not pulling oil back in to it from the reservoir. The tap to the tank should be in the bottom of the tank and not at the top of it. When working correctly, the cylinder should pull almost the same amount of oil from one end to the other. The difference being the volume taken up by the shaft and the little bit of air that remains trapped in the cylinder. The oil has to flow freely from and to the shaft end of the cylinder.

Ramairfreak98ss
04-10-2010, 07:37 AM
what are the sizes of the rams on both trailers? they could have the same surface area between the two just the bigger one is slower as it more area to fill. if you just bought this last year and it never worked since day one why didnt you take it bake to the dealer?

it was a used trailer... built in 2005 and purchased in 2006, it was in pretty darn good condition minus a couple small things and of course this pump issue.

I timed it the other day, with a half load of mulch in my small 14k trailer " so not really stressing the motor bad", took about 42-45 seconds for a full tilt dump.

So the big trailer tilts half way "maybe" in at least 2+ minutes.

Ramairfreak98ss
04-10-2010, 07:41 AM
what are the sizes of the rams on both trailers? they could have the same surface area between the two just the bigger one is slower as it more area to fill. if you just bought this last year and it never worked since day one why didnt you take it bake to the dealer?

could be..

I believe the 20k 8x18 is a 6" bore, 28" stroke and 2.5" wide piston... its damn big! its the rugby LR28a, i guess from looking at it visually.

The 14k trailer has twin probably 2.5" bore, 1.5" piston, ~28" stroke... so nearly the same.

I also feel that since seeing nearly an IDENTICAL trailer on ebay, most have the hoist welded to the frame somewhere around the "middle" of the 18' long trailer frame. Mine is welded in the back 25% part of the frame, in between the axles of the trailer.... I think this makes the 10 ton hoist have the struggle with enough force/pressure to lift 75% of the weight forward of the hoist :/

Ramairfreak98ss
04-10-2010, 07:44 AM
Or something is plumbed wrong. With a double ended cylinder that uses only one end, the shaft end should serve as extra storage for oil. As you say, it may be airbound and not pulling oil back in to it from the reservoir. The tap to the tank should be in the bottom of the tank and not at the top of it. When working correctly, the cylinder should pull almost the same amount of oil from one end to the other. The difference being the volume taken up by the shaft and the little bit of air that remains trapped in the cylinder. The oil has to flow freely from and to the shaft end of the cylinder.

ok, well its only ONE hydro line that goes from the pump to the bottom of the 6" huge hydraulic ram... my 14k trailer has two that go to each hydraulic ram.. so ones double acting and the 20k is single acting, is that good or bad?

Ill check the hydraulic ram to find out if it has a drain on the bottom too.

meador56
04-10-2010, 10:21 AM
uuhhhh noooo

Well yes. Go look at yours, you do have one don't you. My resivoir only holds maybe 1 to1.5 gallons out of the 3 or 4 its takes to operate. Our grain trucks have 5 gallons tanks and 2 of them are double action which means they can pull themselves back down {which is almost never needed}. PTO pumps are faster belt driven are nice but over fill an already over full engine bay. Electric pumps are cheap easy and reliable. Sounds like the problem with Ram air's trailer may be poor placement of the hoist as it should be foward of center.

CLARK LAWN
04-11-2010, 09:52 AM
ya on a double acting cylinder there is oil stored in the cylinder, but not on a single acting cylinder like you first stated.

meador56
04-11-2010, 08:05 PM
ya on a double acting cylinder there is oil stored in the cylinder, but not on a single acting cylinder like you first stated.

Clark the gallon or of oil in that little plastic tank will not hold enough oil to fully extend the cylinder. THEREFORE they store the extra oil in the top side of the cylinder as the pressurized oil moves in the lower end the oil in the top of the piston flows back into the tank then the pump then in the bottom under pressure. This system is on single cylinder scissor type hoist. Twin cylinder hoist just have air in the top. Double action are the same design as the single except they have a valve that can divert the oil to the top side to pull the bed back down. The only time I have had to use this is when hired help raised the bed too high too quick causing grain to pour out over the top of the sides.:hammerhead:

zabmasonry
04-12-2010, 12:06 PM
Operating at 2000 PSI . . .

A 6" bore cylinder can exert approximately 56,000 pounds of force.

A 2.5" bore cylinder can exert approximately 10,000 pounds of force.

I don't think that your problem is with the design or pump. I think that you have a plumbing issue that needs to be sorted out. I don't think that you can really compare the two of your trailers. the 2 cylinder setup only needs to move 1.2 gallons to fully extend both cylinders, the 6" in setup needs to move about 3.5 gallons to fully extend. Remember that the area of a cylinder is Pi*radius(squared) . . . two 2.5" circles do not have the same surface area as one 5" circle.

CLARK LAWN
04-12-2010, 08:18 PM
Clark the gallon or of oil in that little plastic tank will not hold enough oil to fully extend the cylinder. THEREFORE they store the extra oil in the top side of the cylinder as the pressurized oil moves in the lower end the oil in the top of the piston flows back into the tank then the pump then in the bottom under pressure. This system is on single cylinder scissor type hoist. Twin cylinder hoist just have air in the top. Double action are the same design as the single except they have a valve that can divert the oil to the top side to pull the bed back down. The only time I have had to use this is when hired help raised the bed too high too quick causing grain to pour out over the top of the sides.:hammerhead:

so then explain to me HOW the oil getts from one side of the piston to the other on a single acting cyl. I have VERY good understanding of hydrulics and i know how they work but i would like to hear how you think they work.

kc2006
04-12-2010, 10:48 PM
yea a single acting cylinder isn't gunna have 2 lines thus no way to store oil in it. Like clark said, how's it going to come out of the storage side?

The placement of the ram does sound weird, it should be up towards half way mark or 3/4 towards the front. Not sure that would make the issue though, I'm sure they engineered the lift arms differently to make it work better.

CLARK LAWN
04-12-2010, 10:49 PM
ok, well its only ONE hydro line that goes from the pump to the bottom of the 6" huge hydraulic ram... my 14k trailer has two that go to each hydraulic ram.. so ones double acting and the 20k is single acting, is that good or bad?

Ill check the hydraulic ram to find out if it has a drain on the bottom too.

i would go to a hydrulic shop and get the pressure checked. it could very well be a weak relief vavle spring letting the poppet open before the pump builds enough pressure to lift the box.

kc2006
04-12-2010, 10:52 PM
Relief valve? Spring? poppet? pressure? Hell you say?! lol

CLARK LAWN
04-12-2010, 10:56 PM
acually with a 6 in diameter cyl and an operating pressure of 3200( as stated on rugby page) you will about 90,000 pounds of pressure on the ram.

CLARK LAWN
04-14-2010, 08:52 PM
Clark the gallon or of oil in that little plastic tank will not hold enough oil to fully extend the cylinder. THEREFORE they store the extra oil in the top side of the cylinder as the pressurized oil moves in the lower end the oil in the top of the piston flows back into the tank then the pump then in the bottom under pressure. This system is on single cylinder scissor type hoist. Twin cylinder hoist just have air in the top. Double action are the same design as the single except they have a valve that can divert the oil to the top side to pull the bed back down. The only time I have had to use this is when hired help raised the bed too high too quick causing grain to pour out over the top of the sides.:hammerhead:

well im waiting, or do you admit defeat?

Duffster
04-15-2010, 08:49 AM
well im waiting, or do you admit defeat?

Well now Clark that is a tough one to explain. :laugh:

meador56
04-18-2010, 04:28 PM
well im waiting, or do you admit defeat?

No Clark I just emptied a load of pavers we took up and replaced. And when I looked at that ole cylinders barrel right there at the top why right there is a hose that is plumbed into my tank! How else would have the oil capacity to lift it? I am just guessing but I doubt that tank would hold more than 2 gallons full and it stays half full. Now I know we Kentuckians aren't as sharp as an ole buckeye but we have a 26ft Hobbs-Fruehauf 3 Chevy grain trucks and 14X7 gooseneck with dumps and just sold F750 gravel bed. We service what we own and I'll be glad to show all this to ya stop by sometime. We are 3 miles from exit 6 on I-65 between Bowling Green and Nashville. :drinkup: P.S. in our lingo a double action cylinder is one that is power up and power down you can take the same barrel and use it power up only and we refer to it as single action even though it could be replumbed and used as a double.

CLARK LAWN
04-18-2010, 06:25 PM
well what you have is a double action cylinder, regardless of what your "lingo" is. it just uses gravity to force the oil back into the retract side of the cyl. a true single action cylinder only has one hose. an example would be the angle cyl. on a snow plow.

Now if you had bothered to read what the OP stated he says that he has a single acting cylinder, as does the link to the mfg. that would mean ONE hose going to the base of the cyl.