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 | Danny Hsu
Join Date: Posts: 1 
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2001-11-10 33081
I have a 1992 B7100 (HST). I just got a gearmore pallet attachment for my three point hitch and was trying to lift a pallet of brick pavers (400 pieces about 800 lb.) without much success. It lifts my 48" box scraper ok. Can anyone tell me what the lift capacity is? The hydraulic fluid is ok.
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2001-11-10 33082
Tractortips.com doesn't give many stats for a B7100HST. There are stats for a B7100DT, and 1036 lbs. is given as the 3ph lift capacity. There are a couple of things to realize about 3ph ratings. The first is that most ratings have a built in safety factor. The rating usually means something like ' the rated capacity on a centre 2-foot behind the lift arms that can be lifted with acceptable safety levels on level ground and without front ballast.' Yeah it's a mouth full and nothing about rear tire load ratings is even there. Despite the ratings, many 3ph's will lift more than the rated capacity--especially if a lot of front ballast is used and greater risks are accepted. I don't know how the rated capacity on a B7100 should be interpreted. However, between the weight of the forks, pallet etc, the load may be close to the 3ph rating. In addition, loads on standard 4' pallet forks may be centred further than 2' from the lift arms, which would reduce the capacity. Despite the ratings stuff, a pressure test can verify if the tractor's hydraulics come up to pressure specs. My Ford 1710 has a port on the flow control valve assembly that can be used for testing pressures in the lift cylinder itself and not just pressure in the line pressure. Basically, if the lift cylinder pressure is comes up to spec and if the 3ph generally holds up weight while in neutral, then the hitch is probably doing it's job and the load is just too heavy. ....
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| Roger L.
Join Date: Jun 1999 Posts: 0
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2001-11-10 33088
I've seen Kubota literature that lists the B7100HST as being able to lift as much as 1270 lbs "at the 3pt hitch". Competitive brands of tractors list between 500 and 600 lbs as being the weight of an "implement that can be lifted with the 3pt hitch".
It don't doubt that there is some way that the advertising departments can justify the figures that they publish, but personally I prefer your brick and pallet test. I'd be surprised if that size tractor could ever have lifted 800 lbs loaded as that type of pallet requires. The tractor itself (bare) only weighs 1268 lbs. with most of that being toward the rear wheels. Although it would be easy to design it to lift 800 lbs, the the front wheels would be pawing the sky! Listen for the relief valve. If it is squealing then you are probably asking too much. By now I'll bet you have taken off some of those bricks until it lifts the load. I'd be curious to know your estimate of the weight?
As Tom suggests, you could check if the hydraulic system is getting up to the proper pressure. This test is so basic that there is a hydraulic gauge port on every tractor I've ever seen. A ten dollar welding pressure gauge is the only tool that you need for this test. Just thread the gauge into that port and then watch it as you try to lift too heavy of a load. The relief valve is responsible for setting thhe upper limit on the system pressure. With the gauge you are testing two things: the ability of the hydraulic pump to generate enough pressure, and confirming that the setting of the relief valve is not blowing off the pressure too soon. The pressure should rise to whatever the standard system pressure is that is listed for your model tractor and at that point the relief valve will squeal. If it does those two things then you can assume that the rest of the 3pt lift is doing its job.
The only listing that I have for the B7100HST system pressure shows it as being 1450 psi....but again this comes from advertising literature and not from a shop manual. Can someone else confirm this pressure for us?
....
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| charlie
Join Date: Posts: 1
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2001-11-10 33092
let's don't look at specs,buy pressure gauges,or listen to the relief valve.lets think about this load.a 2 pound paver?i don't think so.most of the old pavers i mess with are 6 pounds plus.i used o have a B1550 and put a 5'6 brillion behind it and only had to put two 35# suitcaseon the bumper to keep it down.good luck ....
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| Roger L.
Join Date: Jun 1999 Posts: 0
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2001-11-10 33093
charlie, I don't think Danny's problem is exactly what the weight is as much as the tractor not being able to lift it. By the way, what is a brillion? ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2001-11-11 33100
I'm curious about variation in system pressures on different tractors. I don't know about the 7100, but my Ford 1710 specs 1846 lbs. I don't know why but I thought pressures around 18 - 19 hundred were sort of standard for compacts. I think farm tractors tend to be higher around 2100. My backhoe specs a preferable pressure range of 2000 - 2200 lbs. and a minimum of 1500 lbs. I imagine that my hoe would work at 1400 lbs. but probably wouldn't dig well in many soils. Anyway, I guess that implements such as hoes and log splitters may not work that well of tractors with fairly low relief-valve settings and that might be something to check when looking to buy a tractor. One comment about lifting the pallet of bricks: The 3ph still might lift the pallet (given adequate front ballast) if the relief valve isn't opening, although trying might not be too desirable. The volume of oil a pump delivers decreases as the operating pressure increases. At pressures near the relief valve setting, very little volume may be pumped at idle rpm's. The lift cylinder on my 3ph forklift will lift quite a bit more than the 3ph will. It's not uncommon for me to have a load on the forks and find that the 3ph won't lift it much. Often it will lift if I throttle up to pto rpm and wait. Of course, the forks rather than the 3ph generally do the lifting, but sometimes it’s desirable to raise the 3ph so the forks can be angled down with the carriage tilt. Getting pallets on or off the forks on uneven ground can be tricky, and it’s handy to have three piece forks and carriage tilt. ....
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