Hydraulic Brush Cutter Connections?

[GATC35]

I recently purchased a used 5 ft. hydraulic driven brush cutter for my Bobcat T190. During the sales transaction the gentleman I was purchasing if from said "I wish you have more luck with it than I did", He went on to say it never performed very well, and seemed really slow and stalled easily. I had driven 200 miles to buy this thing and was in a hurry to get back home. I looked the mechanical side of the cutter over really well but never paid much attention to the hydraulic hoses. When I got home and started to hook the hoses up I realized the problem. The hoses were only 1/4 inch diameter. I'm no hydraulic expert but I know those hoses are too small. So what size hoses should be installed? Seems to me 1/2 or 3/4 would be more appropriate. My Bobcat puts out 16.9 GPM, the motor only has a part number and a serial number on the data plate. No PSI, or GPM rating, also no manufacturer. The fitting in the motor is a straight thread with a o-ring that measure .865 on the outside diameter of the threads. So is this a "SAE O-ring #10" fitting?

So my questions to you hydraulic experts are:
What size hose? 1/2 or 3/4 Not much price difference between the two.
What size fitting is in the motor? I think it must be a "SAE o-ring #10"

Thanks..........

 

[kennyd]

HERE is a chart that will help you determine the port size and hose size.

Looks like it is a #10 fitting and 3/4" hoses would be best.

 

[Heavyduty]

I recently purchased a used 5 ft. hydraulic driven brush cutter for my Bobcat T190. During the sales transaction the gentleman I was purchasing if from said "I wish you have more luck with it than I did", He went on to say it never performed very well, and seemed really slow and stalled easily. I had driven 200 miles to buy this thing and was in a hurry to get back home. I looked the mechanical side of the cutter over really well but never paid much attention to the hydraulic hoses. When I got home and started to hook the hoses up I realized the problem. The hoses were only 1/4 inch diameter. I'm no hydraulic expert but I know those hoses are too small. So what size hoses should be installed? Seems to me 1/2 or 3/4 would be more appropriate. My Bobcat puts out 16.9 GPM, the motor only has a part number and a serial number on the data plate. No PSI, or GPM rating, also no manufacturer. The fitting in the motor is a straight thread with a o-ring that measure .865 on the outside diameter of the threads. So is this a "SAE O-ring #10" fitting?

So my questions to you hydraulic experts are:
What size hose? 1/2 or 3/4 Not much price difference between the two.
What size fitting is in the motor? I think it must be a "SAE o-ring #10"

Thanks..........

Put the correct hoses on it and the cutter should work well. Can you take some pics? Is it the Bobcat brand cutter?

 

[Wayne County Hose]

One thing to keep in mind. A 1/2" hydraulic hose with crimps does not have 1/2" of flow. If you measure the ID of a 1/2" crimp fitting, most are just over 3/8". a 1/4" crimp flows about 1/8". You can almost figure on a crimp fitting knocking you down to the next lower hose size as far as flow goes.

 

[Discount Hydraulic Hose]

One more thing to consider is the working pressure of the hose you'll be putting on your equipment. If you use SAE 100R2AT hydraulic hose, a 1/2" hose is rated for up to 3500 psi, while a 3/4" hose is rated for 2250 psi.

You can also buy a heavier-duty hose, though I doubt that will be necessary. If this becomes an issue, SAE 100R17 is rated for 3,000 psi in all sizes, and SAE 100R12 (four-wire) is rated for 4,000 psi at the sizes you are considering.

Ken

 

[Wayne County Hose]

One more thing to consider is the working pressure of the hose you'll be putting on your equipment. If you use SAE 100R2AT hydraulic hose, a 1/2" hose is rated for up to 3500 psi, while a 3/4" hose is rated for 2250 psi.

You can also buy a heavier-duty hose, though I doubt that will be necessary. If this becomes an issue, SAE 100R17 is rated for 3,000 psi in all sizes, and SAE 100R12 (four-wire) is rated for 4,000 psi at the sizes you are considering.

Ken

Good point Ken, I forgot about the big drop in the max pressure going from 3/4" to 1/2". I think that 1/2" will be more than plenty for this mower. I'm surprised J_J hasn't weighed in on this one. He's real good with figuring gpm and sizes and all that good stuff.

 

[SPYDERLK]

One thing to keep in mind. A 1/2" hydraulic hose with crimps does not have 1/2" of flow. If you measure the ID of a 1/2" crimp fitting, most are just over 3/8". a 1/4" crimp flows about 1/8". You can almost figure on a crimp fitting knocking you down to the next lower hose size as far as flow goes.

The thing is that the influence of the diameter reduction is only for a short distance. Of course it adds to the flow resistance of the hose, but it comes to a smaller and smaller proportion as the hose lengthens. I bet you have some tables that tell pressure loss at various flows with the std fitting sizes.. .. Im guessing 20gpm warmed oil thru a 3/8 hole/1/2" fitting would lose less than 50psi. Real data would be usefull tho.
larry

 

[kennyd]

One thing to keep in mind. A 1/2" hydraulic hose with crimps does not have 1/2" of flow. If you measure the ID of a 1/2" crimp fitting, most are just over 3/8". a 1/4" crimp flows about 1/8". You can almost figure on a crimp fitting knocking you down to the next lower hose size as far as flow goes.

I think that 1/2" will be more than plenty for this mower.

I agree with what you said in the first quote 100%, and given that you really think 1/2" hose will flow 19GPM? Seems 3/4" is the best to me...but I am just a hack-not a professional like you

 

[Discount Hydraulic Hose]

I'm not really good at calculating flow and pressure drop, but my gut instinct is that a 1/2" hose should work well. We sell tons of quick disconnect couplers for Bobcats and such. The size that almost everyone uses? 1/2" couplers with 1/2" NPT thread connected to 1/2" hoses. It seems unlikely that this attachment would require larger than that, especially considering the last guy had it running (although poorly) on 1/4" hoses.

By the way, if you still can't make up mind between 1/2" and 3/4"? There's always 5/8" available.

Ken

 

[GATC35]

Thanks allot for everyone who responded to this question. I did run the cutter with the 1/4 inch hoses and it was really bad, slow, no power and kept stalling. Now I know why the guy wanted to sell it. After looking at all the flow charts I decided on 3/4 inch hoses. I looked at some other cutters with the same GPM rating and they use 1/2 hoses. I do have one 90 degree bend at the pump connection, so I decided 3/4 was probably best. The price difference was only about $20.00 comparing the 1/2 vs. 3/4 inch hoses and fittings. When the fittings arrive next week I'll get some pics of them side by side, 1/4 vs 3/4. Also I think it was "HeavyDuty" wanted a pic of the cutter, it may take me a while but I'll get one.

I hope this makes sense. Right now I'm dead dog tired. I'm at my other house back in the home land, Alabama. I had to dig out and level a 4 foot by 4 foot area for some concrete steps today. Well I wound up doing it all by hand, yep pick and shovel. I have a tractor with front end loader with backhoe, and a Bobcat back in Georgia and I'm digging in rock hard red clay by hand. Of course the temperature was above 90 with 90% humidity. My wife took great pleasure in reminding me of all the equipment I had back in Georgia.