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Randy Bennett
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2001-10-22          32595


I have a Shibaura SD 1843. I have been loking for a loader for it. I have seen several posts pro and con regarding Homestead Tractors. I have also been wondering about Koyker or Kelly. I understand that there is no mounting kit available yet for the Kelly or Koyker.My questions are...What you folks think about the overall quality of these three brands of loaders??Have you had trouble with any of them?Did you have to fabricate a mounting system to fit your tractor?Are there other brands I should look at??Thanks...



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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-10-23          32616


An Allied 195 came with my used Ford 1710. Allied are moderate priced decent loaders that lack features found on more pricey makes. It has served me just fine, although some times I wish for the selectable slow/fast dump speed feature found on some JD models and others. When selecting a loader, power and speed are trade-offs. The pump on my 1710 is 8.1 rpm. Given the loader, I occasionally have to work around a load I can't lift directly. More often I'm aggravated by having to wait to the slow dump to work. Of course, I've got gears and do most loader work at low RPM's. HST's have better control over ground speed vs. engine rpm, and I suppose I'd be less aggravated. Still do like my gears though. ....


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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2001-10-23          32624


Tom my northern neighbour you're the lucky(?) recipient of today's 'Murf's Ridiculously simple Idea'. Today give-away is the $10 (Canadian funds even) "slow dump" option for loaders not otherwise equipped. Go to your local (ok, not local in your case) hydraulic supply shop and buy a high pressure ball-type valve (shut off valve). Before installing it in line with the dump circuit of your bucket, close the valve and carefully drill a small hole through the ball only. Carefully clean all loose metal particles out of the valve and install it next to the valve body in the 'bucket dump' line (the side of the cylinder furthest from the bucket) which connects the valve body to the bucket curl circuit. This modification can also be used to control cavitiation in the lowering circuit of the loader. The big advantage of doing this modification over just installing an anti-cavitation valve is that it can be 'undone' when it is not required (such as when working with light material like snow) or when raising the bucket, not dumping. Best of luck. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-10-24          32638


Interest idea. If I've got it right, the valve would be installed in the return line of the dump circuit and act like an on/off flow restrictor. I guess what happens in dumping a heavy load is the curl cylinders nudge the bucket 'over the edge', then the weight of the load tries to push oil out the unobstructed return line faster than the pump wants to put oil into the other side of the cylinder. The result is that the oil cavitates, which means that most of the load dumps fast. Then, the bucket stops and there's a long pause before it finishes dumping. Sounds like some flow restriction would improve the situation. At least I wouldn't be 'ho humming' during each dump while waiting for the bucket to start moving again. I guess there's also the possibility of installing a regenerative dump circuit to get a genuine fast dump. I don't know if it's feasible, but I think of a regenerative circuit as sort of a float circuit that gets pressure. I know that individual control valve sections can be bought for some SCV assemblies, and valve sections with or without float can be bought. What I don't know if valve sections that have a regenerative circuit at a detent position exist. If so, then the thing would work so that ordinary operation produces a normal dump. Shove the valve into detent and it gives a fast dump, but with much less power. However, even if such a thing exists, I don't imagine that it would be a $10 solution. ....


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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2001-10-24          32642


Tom my friend, you are very close, but not quite there, the problem with cavitation is not that it affects the speed of dumping the bucket or lowering the boom, because it actually speeds (very slightly) the process, since air travels easier than hydraulic fluid does. The problem IS the air, since it is compressible it acts like a big spring in the circuit, so much so that it would in a severe instance, basically prevent all down pressure in the loader until it was purged. Further, the point you raise about the weight acting as a pump is correct, most people perform dump or lowering tasks at idle speed with the valve wide open and use the rev's to boost pump performance only for 'work' functions, lifting, curl up, etc., allowing gravity to acts as the 'pump' for dumping in fact boosting pump output in the 'dump' functions will mitigate the cavitiation by speeding up the replacement of fluid. The trick is to learn to move the valve less and the throttle more during dump operations, in fact I have seen several loaders with adjustable 'stops' (in some cases dump valves with an adjustable detent position) which restrict the dump valve motion to one which restricts cavitiation to a bare minimum. By the way, these 'adjustable' restrictors are fantastic additions to remote circuits where many different cylinders are used for different funtcions, small cylinders, such as those used for upper links move VERY fast compared to larger more voluminous cylinders such as those found on log splitters. This results in very 'twitchy' performance, you hit a little bump while angling a rear blade and it moves way to far, now you have to go back over that spot, by restricting the line to small cylinders you can even out the performance speed and take away a lot of that 'twitchyness'. Best of luck. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-10-25          32657


Murf: That was actually my read on it--wouldn't affect the speed much, just take the pause that follows after most of the load dumps. It might seem faster even if it isn't. My aggravation is that when I'm dumping while on a slope, I have to hold the tractor with the brakes, which are on the same side as the foot throttle so I can't easily increase the rpm. The situation is about the only time I wish for HST. But as aggravations go, it's not huge. Guess I've always got the option of using a lower range and running higher rpm, but the ground speeds in the next lower range are pretty slow. Hummm, maybe another case for HST, but I'll probably always like my gears. A remaining mystery for me in this cavitation stuff is where the air comes from. It would be on the pressure side of the cylinder I guess. I never thought of oil as having much of a partial pressure that would produce vapour in a vacuum like water, nor have I thought of air as very soluble in oil. Could be but I just don't know. About the only source externally would seem to be air drawn into the cylinder around the piston seals, which seems a more likely explanation. Of course, all this kind of stuff doesn't make me operate the tractor any better. It's just comforting to have a sense of how it all works. Yesterday was my birthday, and your <$10.00 solution wasn't bad coming on that day. ....


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CaseyR
Join Date: Jun 1999
Posts: 53 Columbia River Gorge, Oregon
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2001-10-25          32666


TomG, your oil probably does have water vapor in it, which could increase the chance of cavitation occuring. Even without water present, oil is a complex mixture of hydrocarbons so you would get various partial pressures of the components. But, then, I'm not an engineer and I don't really know anything about the properties of hydraulic oil.

While these don't really answer anything regarding the current discussion, they might be mildly interesting to some:
http://www.allstar.fiu.edu/aero/Hydr06.htm
http://abe.www.ecn.purdue.edu/~abe435/statement.pdf.pdf
http://www.osmonics.com/products/Page785.htm
....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-10-26          32670


Casey: Thanks for the links. I checked the first link, which went directly to a description of cavitation. The description was in terms of vapour pressures, so that's probably my explanation. Come to think about it, when I've left oil in a skillet long, I've probably been aware that oil does have vapour pressure. I guess that in a hydraulic system the vapour forms due to low-pressure rather than high-heat. The vapour probably disappears as soon as the pressure increases. Of course, any water or air in the system could contribute to vapourization. That’s probably why I said 'partial pressure' rather than 'vapour pressure' when I was first wondering about this. Ah, an explanation, so now I can get back to more practical matters like wondering if the flat I fixed yesterday held pressure overnight. ....


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Peters
Join Date: Feb 2002
Posts: 3034 Northern AL
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2001-10-29          32733


The vapor pressure of the oil definately has an effect on cavitation and air/vapor in the oil. Work done to the oil will reduce the hydrocarbon's chain length and increase the likelihood of cavitation. You may also notice that the amount of cavitaion increases as the tractor warms up and the temperature of the oil increases. PV = nRT note the Temperature term.
Also having worked with vacuum systems, remember the axium " Nature abhores a vacuum". A small leak on a vacuumm system can be very difficult to find and a very small mass of air leaked into the system in the vacuum can have a very large volume P1V1=P2V3. The hydralic cylinder and lines in vacuum due to the weight in the bucket can have air leaks that are incapable of leaking oil. They are very difficult to detect.
Peters ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-10-30          32763


Peters: I hadn't made the connection that one tiny air bubble could completely fill the cylinder with air if the vacuum was sufficient. I was again muttering about my slow dump times the other day. Guess I try to figure out if they are abnormal or not. I know that oil cavitating in the pump can ruin the pump, but I don't know if cavitation in a loader cylinder and lines would add to wear and tear. I'm making an assumption here that cavitation during dumping would be confined to the cylinder circuit. Well, maybe I should give up and a install flow restriction such as Murf suggested or maybe just run at higher rpm's. ....


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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2001-10-30          32777


Tom, I think part of your confusion of where the air comes from is in not thinking of the 'big picture' in the operation of your hydraulics. Yes, the air is appearing on the 'pressure' side of the system, but the pump is far from a sealed unit as most people think of it being. Further, it is only 'pressurized' on one side, the other is merely connected to the sump in the reservoir. If you apply a vacuum to the 'pressure' side of the pump air will 'burp' through the pump much easier than a viscous liquid such as the hydraulic fluid can move through, resulting in air bubbles on the 'pressure' side of the pump. Best of luck. ....


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Peters
Join Date: Feb 2002
Posts: 3034 Northern AL
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2001-10-30          32793


Rethinking the problem you could have a small air leak in the system. The leak does not necessarily need to be in the curl mechanism but could be in any area where the lines see vaccuum.
You tend to get a small stream of bubbles with a small leak. These do not necessarily have time to surface in the oil resevoir. As they are small they will not necessarily affect the pump, under pressure they will collapse into smaller size. In the vaccuum section they will expand rapidly and then hold volume until the pump catches up. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-10-31          32805


Murf, Peters: I think it's great that subjects like this can be pursued a bit here. Thanks for the comments. At the moment, I not actually feeling confused, but in the past I know feeling unconfused might be cause for me to worry. The feeling of having knowledge is a sure sign of ignorance or some philosophical stuff like that. But I do think that I’ve mostly got it. I'm aware that something like a small leak in the suction line or filter assembly could produce exactly the condition described. Normal operations also probably can put air in the system. If the tractor drives over a bump, it might slosh the oil in the sump enough to get some air in the oil that wouldn’t bubble back out before it gets picked up by the suction line. Of course, I have to keep in mind that I really don't know if the operation of my loader is abnormal or if I'm just impatient. Anyway, I'm just happy to get some additional insight into the physics of it. Lord, I both happy and unconfused? Now I'm sure I should start worrying. ....


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Peters
Join Date: Feb 2002
Posts: 3034 Northern AL
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2001-10-31          32812


Tom;
I am not sure of the dynamics in your case. I know that the bubbles can form on the negative pressure side and cause problems.
I worked with RIM (Reaction Injection Molding)equipment a number of years ago. My self and a friend developed an optical resin system and tested it on a number of RIM machines. The RIM process injects 2 liquids together at high pressure. I circulates the liquids at high pressure and then switches to impinge the liquids together for mixing. I chased bubbles in these state of the art systems for a year developing the process.
As the liquids were clear and the cirulating tanks had sight glasses we might spend a day tightening the fittings before starting work.
Peters ....


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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2001-11-01          32873


Of course the easier, slightly more expensive route is to place a "counter balance valve" which is a fancy term for an "automatic" proportioning valve (Tom, Princess Auto Catalog # 1240065, on sale this week, Happy Birthday) which limits the flow of the return line to match that of the pressure side of a circuit, thus preventing load-induced cavitation automatically. Best of luck. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2001-11-01          32875


Gee, a princess for my birthday! Ah shucks, the position is already taken, and she would seriously object to being characterized as a princess. But thanks; I think my brother-in-law did leave me a PA Catalogue the last time he was here. However, I don't think I'm going to launch any tinkering projects till spring, and the first project next spring may be a heated shed. Dang, I get tinkering urges during the winter and there's no warm place to work. I might start by tracking down if control valve sections are available that have a regenerative circuit on a detent position. Such a thing may be ideal for my situation. Thanks again guys. After I started making connections between my loader hydraulics and what little physics I retain, I can well understand why Peters and crew spend a day just tightening fittings. I recall that there often is some extensive technology used just to get liquids mixed in similar applications, let alone the problem of bubbles in the liquids. ....


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