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.

 

[Discount Hydraulic Hose]

Hey, look at it this way. That other guy was obviously frustrated and anxious to sell the cutter because it didn't operate properly. You probably got a great deal on it, and for the cost of a few houses, it will probably run great for you.

You made out famously. That other guy would be kicking himself for not knowing that all his cutter needed was the right size hoses.

 

[GATC35]

The fittings arrived yesterday. So when I got home from work today I installed the new fittings and lines. It made all the difference in the world. This thing really performs well now. No low speed, no loss of torque, no stalling. Woo Hoo ! I only had two problems. The new fittings were longer than the old fittings, which caused them to hit the deck. Since the connections were on bottom I disconnected the motor and rotated it 180 degrees to where the fittings are on top.. Anybody see anything wrong with doing this? Rotating the motor caused problem number two because the cover now won't fit. I'll fire the plasma cutter up and cut a small opening in the cover where it will fit over the motor. Anyway here's some pics, I know ya'll like pics. The first three are of the fittings and hoses. Next two are of the drive motor and gearbox. Then a pic of the cutter and Bobcat. Two pictures taken of my test area where I cut some brush. My dog Molly is the inspector. The last picture shows the problem with the cover not fitting.

Thanks again to all who replied.

 

[jinman]

Nice! It's just amazing to me that the previous owner would try to operate that cutter with 1/4" hoses.

 

[kennyd]

Great pictures Mark...what a contrast between the hoses and fittings!

 

[kennyd]

Nice! It's just amazing to me that the previous owner would try to operate that cutter with 1/4" hoses.

Yeah, and worse yet is he probably bought it from a dealer with them already installed-because it was the cheapest I'm sure.

 

[Wayne County Hose]

Why didn't you go with a sweep 90 crimp like the 1/4" hoses? What you did is infinitely better than what you had but that's why you have a clearance issue. Also, the third pic fro the left with the QD's, you have 3/4" hoses then drop to those little qd's and the reducer fitting. I know you wanted 3/4" hoses for flow, but you would have been better off with 1/2". With 1/2" hoses, you could have used a 90 degree O-ring crimp and not had a clearance issue. 1/2" hose is also way more durable than 3/4".
Good thing for plasma cutters and it's great that Molly approves.

 

[GATC35]

WCH,

Thanks for your input. After I finished and stood back and took a long look I realized I could have done several things different. The hose could have been 1/2 inch which would have solved many problems like you mentioned.

Thanks...

 

[Discount Hydraulic Hose]

The picture with quick disconnect illustrates the problem well. Like jinman said, it's hard to imagine why the previous owner didn't see it. But hey hindsight is always 20/20.

And I'm in agreement with WCH, that elbow would be better with an ORB 90ｰ crimp fitting or even a JIC female 90ｰ crimp. What you have now is three fittings and could have been two or even one. Also, the other way would have avoided using pipe thread, which is more prone to leaking down the road than JIC or ORB.

I'm glad you've got the cutter working properly now. And thanks for sharing the pics. The discussion here, along with the pics you posted, should help other people to identify and correct similar problems they may be having with their own equipment.

 

[zman007007]

I would recommend a divorce,after the wife"s comment, but then it would be your wife on here asking questions about tractors. LOL

 

[GATC35]

Well the steps were for her. That's a cabin on the lake with the washer and dryer downstairs in the basement. The only way to the basement is outside around the front porch. She wanted a shortcut to the end of the porch. So we bought some precast concrete steps. I got rewarded later with bar-b-q chicken, baked tater, and corn on the cob. Of course a cold adult beverage. So no divorce...........I'm keeping this one.