Towable backhoe

[12barber12]

Again thank you guys for putting the effort in to help me fix the problem I greatly appreciate it

 

[tcreeley]

I have a Northern Tool trencherman mini backhoe. It came with a single stage 1.2 gpm pump which was too slow for me- swinging the bucket side to side for next scoop. I swapped the pump for a 2 stage 11 gpm/2.9 gpm pump like this one - Concentric/Haldex Hydraulic Pump 11 GPM, 2-Stage, Model# 1001689 | Pumps| Northern Tool + Equipment . I swapped out the 5hp motor for a Tecumseh 8 hp. I've had it for close to 20 years and it works great.

Pump Specs:

View attachment 270095

 

[dfkrug]

I have a Northern Tool trencherman mini backhoe. It came with a single stage 1.2 gpm pump which was too slow for me- swinging the bucket side to side for next scoop. I swapped the pump for a 2 stage 11 gpm/2.9 gpm pump...

Yeah, my CADDigger was too slow also. If I had kept it, I was going to to what
you did. 2-stage pumps make a lot of sense in this application. Glad it worked.

 

[chad22]

I have a Northern Tool trencherman mini backhoe. It came with a single stage 1.2 gpm pump which was too slow for me- swinging the bucket side to side for next scoop. I swapped the pump for a 2 stage 11 gpm/2.9 gpm pump like this one - Concentric/Haldex Hydraulic Pump 11 GPM, 2-Stage, Model# 1001689 | Pumps| Northern Tool + Equipment . I swapped out the 5hp motor for a Tecumseh 8 hp. I've had it for close to 20 years and it works great.

I guess they do work on backhoes then. Good to know. That's the same kind of pump I was gonna put on my excavator, (Since they had one at Tractorsupply) But didn't think it would work right. So I ordered a pump on ebay, turns out it was the wrong one and required more hp. I decided to keep it though as It was only $60.00 for a $300.00 pump. (Might make a logsplitter with it) I have a mazda B2000 pickup truck engine that will power it.

Then that's when I went looking again on ebay and came across the cheap pump.

Chad

 

[chad22]

Again thank you guys for putting the effort in to help me fix the problem I greatly appreciate it

No Problem. Hope you get it working. The backhoes are a lot of fun. I'm always trying to find uses for mine.

Chad

 

[J_J]

It only takes about 8 HP to get 4 GPM at 3000 psi.

There is no advantage what so ever in using a two stage pump.

The two stage pump will be switching back and forth with the pressure with no load or little load and be slow when you really need the muscle.

If you want power, go for the single stage pump.

 

[tcreeley]

It only takes about 8 HP to get 4 GPM at 3000 psi.

There is no advantage what so ever in using a two stage pump.

The two stage pump will be switching back and forth with the pressure with no load or little load and be slow when you really need the muscle.

If you want power, go for the single stage pump.

I used a 2 stage at the time because I was in the middle of doing a log splitter and had the 2 stage 11 gpm pump. I was getting frustrated with how slow my backhoe was with a 1.2 gpm that I thought why not. It made a huge difference in speed. What does happen is that I break the lower cylinder pin from stress cracks and bends in the steel- I'm cheap and have bought a cold rolled rod and cut and drill myself a new pin when I need it. I had the backhoe rewelded when I split the horizontal 2 x 1/4" square tubing that served as the cross member for my out rigger supports. Slow split- I wanted to finish the job before I had it welded - about 2 ft. It was like having a built in spring seat for a while! Solid now! Even though a mini back hoe is small- it still exerts a good deal of force. Many home builds are not beefy enough to hold up. They should be absolutely rigid with out any flex possibility.

 

[dfkrug]

It only takes about 8 HP to get 4 GPM at 3000 psi.

The SurplusCenter calculator says you need about twice that power when
using a gas engine for that kind of flow/pressure.

To move my 3" cylinders fast enough under low load condition would
require more flow than I had, and my 10hp Tecumseh did not have the
power to pump that kind of flow at my relief setting.

A two-stage would have solved my problem with such a weak motor
and large cylinders.

 

[J_J]

Hp to drive hydraulic pump = Psi x GPM / 1714

3000 x 4 / 1714 = 7.001 HP

Pumping = 1 Hp = 1 GPM x 1500 Psi

Electric hyd HP

flow rate (US gal/min) × pressure (psi) / 1714
= 550 ft·lbf/s
= 745.699872 W = 1HP

 

[Iplayfarmer]

Hp to drive hydraulic pump = Psi x GPM / 1714

3000 x 4 / 1714 = 7.001 HP

Pumping = 1 Hp = 1 GPM x 1500 Psi

Electric hyd HP

flow rate (US gal/min) × pressure (psi) / 1714
= 550 ft·lbf/s
= 745.699872 W = 1HP

As I understand, JJ, those are pure conversion numbers that don't take into account any kind of mechanical losses.

 

[J_J]

Yes, that is true, but if things are not leaking, or bypassing, the fluid supplied to the IN port should all come out the OUT port. So if the design of the pump was to pump so many cc's or cu in's, then at some rpm, all the same kind of pump should pump the same volume.

 

[12barber12]

Hi all I'm back again with more questions I've been messing with my homemade backhoe and people have been telling me that the fluid is getting too hot that is why am losing pressure any ideas on what I can do

 

[Iplayfarmer]

Hi all I'm back again with more questions I've been messing with my homemade backhoe and people have been telling me that the fluid is getting too hot that is why am losing pressure any ideas on what I can do

Bigger tank.

 

[john_bud]

Add a electric fan and oil cooler after the filter before the tank

 

[davedj1]

12barber12, where are you located? The reason I ask is that I have a 17 gal tank and a couple of single stage pumps that may be of use to you. Of course if you are too far shipping won't make it feasable.
good luck,
dave

 

[12barber12]

Cleveland ohio

 

[3v0]

Hi all I'm back again with more questions I've been messing with my homemade backhoe and people have been telling me that the fluid is getting too hot that is why am losing pressure any ideas on what I can do

I had been wondering why mine came with a 12 gallon tank.

 

[12barber12]

Does Anyone know what would cause Hydraulic fluid to look like this

 

[Farmerford]

I think that is entrained air from one of three sources: a leak in the suction line from your tank to the pump or an undersized tank or the use of a fluid that does not have additives to reduce air entrainment.

The tank size is important for cooling, but it also affects how quickly entrained air that normally does get into the fluid comes to the top (like in your jar of fluid) and how well contaminants settle out of the fluid. THe larger the tank the longer each bit of fluid gets to rest before it goes through the pump again. If the discharge from the return line filter into the tank occurs above the fluid level aeration can occur. iF the discharge outlet for the return line is too small it will create a fast moving stream of fluid that stirs the tank and causes aeration. Some outlets have a diffuser inside the tank to soften the stream of returning fluid.

Fluid with air entrained is compressed as it goes through the gear pump and the actual volume of fluid pumped is reduced by (almost) the amount of air. If your tank is too small and the fluid gets hot, it thins out and the internal leakeage in the pump increases. It is possible that a combination of air entrainment and increased leakeage due to heat would limit your pump's output.

 

[12barber12]

Thank you so much it explains a lot why I'm losing pressure after running it for a while it has to be to small of a tank it currently has a 5gl do you think a 10gl will be good enough