DOM Tubing??

[poohbear2767]

First questions, what does DOM stand for.

I have a 3/4 shaft mounted on pillow block bearings.

I have a tractor with a shaft coming off the PTO
and the yoke on the other end fits a 1.25 shaft.

So to drive the 3/4 shaft off the tractor I need a bushing to adapt it.

Something like this from McMaster Car.
Part Number: 7767T691 $23.63 + shipping.
This comes in 1 foot long size, I only need about 3 inches.

OnlineMetals will sell me 3 inches of DOM tubing for $3.42 + shipping.

Tractor PTO is rated at 540 RPM, so I'm thinking 600 RPM max.
And I plan to use this at idle speed, so probably 200 RPM.
The pump motor is rated at 2800 RPM. So 1:14 increase does that.

I'm using this to drive a 1/2 HP water pump.
This is one of those little cheap Harbor Freight clear water pumps.
Cost about $35. The motor is severely underated. But it pumps great.

I don't have a generator. And I can't run electric that far to power the pump.
So I removed the fan cover and the fan impeller from the back of the pump motor and replaced it with a lovejoy coupling. I built a 1:14 belt and pulley transmission to drive the pump off the tractor PTO.
The tractor can sit there at idle and pump water and not use a lot of fuel.

I tried running the pump off of an inverter hooked to the tractor battery
but I had to run the tractor at full power to keep up with electrical load.
This is an antique tractor. 1949 8N. Must have a weak alternator.

So, opinions on using the DOM tubing??

Thanks.

Pooh Bear

[RET]

Hi,

Can't tell you for sure what DOM stands for, but its probably some sort of heavy wall drawn mechanical tube.

I do have a couple of other concerns though. First, aren't most tractor PTO shafts splined? Any that I've seen are. If so, while the shafts are hardened, you really need the spline connection to transmit the torque you require; a straight keyway is going to be iffy. Remember, if you are doing a speedup of 14:1, you are also increasing the torque on the PTO by more than 14 times (because of losses), so even on a little pump, the torque will be fairly high. You don't want to take a chance on damaging the PTO shaft.

Second, both pumps & PTO shafts are designed for straight torque, not side loading, so be sure you take that into account when you design your speedup pulley system.

I hope this helps, although you may already have considered this.

Richard Trounce.

[jwekalaka]

AS far as I know, DOM is drawn over mandrel

Jon Wimmer
Ekalaka MT

[poohbear2767]

The other end of the PTO shaft is splined to fit the tractor PTO.
The end I am working with is smooth bore.
This is the PTO shaft off of my brush hog.

I won't be hooking directly to the pump.
I will be hooking to a belt and pulley transmission.
The shaft I will hook to is on pillow block bearings.
And it will sit almost directly inline with the PTO. As close as I can get.
So not much side loading there.

The electric motor on the pump is rated at about 375 watts.
That's where they get the 1/2 HP rating. (yeah, right)
But I think the motor is no where near 1/2 HP output.

The tractor PTO is rated 540 RPM and 23 HP at 2/3 throttle.
I plan on running it at just above idle. Should be plenty to run this setup.
If that little motor can run it off my 700 watt inverter I think
my tractor PTO can surely drive the pump at idle.

Pooh Bear

[Steve_in_Mich]

belt and pulley transmission?

You can purchase a 1-1/8 6 spline to straight shaft coupler at TSC. You can choose from a variety of ID sizes. I run one on my 8N to drive a hydraulic pump for my backhoe.

I think your PTO speed is only going to be about 66 RPM at 200 RPM motor speed. If correct that will require a 42:1 speed increase to get the pump to 2,800. Much more than a single step pulley to pulley will provide. I'm sure the tractor will not feel the addition of a pump and gearbox to get the job done. If you have a Sherman Step-Up transmission it will increase the PTO speed by an additional 60%. If the pump is a NON-positive displacement type (i.e., centrifigal) you will need to get the RPM's high enough to cause flow, where a gear or piston pump will have some output even at low speed but proportional to speed.

I don't know your pump application but would it be possible to set up an elevated loop that you only have to get started and then let siphon take over?

[poohbear2767]

PTO speed for the N series tractor is engine RPM divided by 2.25
Idle RPM is 450. Divide that by 2.25 and you get 200.

I updated my old 1 1/8 shaft to the modern 1 3/8 shaft.

I have all the pulleys, shafts, and pillow block bearings.
All I had to buy was the lovejoy coupler and a couple of belts.

This transmission works in two step ups.
First the PTO drives a shaft with a 12 inch pulley. 200 RPMs
The twelve inch pulley drives a 3 inch pulley. 1:4 increase, 800 RPMs
On the same shaft as the 3 inch pulley is a 7 inch pulley.
The 7 inch pulley drives a 2 inch pulley. 1:3.5 increase, 2800 RPMs.

I'm pumping water from the Sequatchie River up to my House.
It's about 15 to 20 feet gain in elevation. The pump handles it just fine.
But the river is 500 feet from the house. Can't afford to run electric down there.

Pooh Bear's Place

I plan on getting a bushing to bring the 3/4 shaft up to 1.25.
Then weld it onto the shaft and drill a hole thru it for the shear pin.

I just needed to know if DOM tube will work for this.
Never worked with the stuff before that I know of.
Didn't even know what it was till yesterday.

Thanks.

Pooh Bear

[Booger]

It will work fine,That's what the driveshaft in a car is made out of.DOM means drawn over mandrel,so that you get a consistant size/round tube.

[poohbear2767]

I placed the order on Sunday evening with Online Metals.
Expecting to get it any day now. I ordered a 4 inch piece.

Thanks.

Pooh Bear

[poohbear2767]

Got it today.
The inside diameter is a little undersize.
But I can work with this.

This project is coming together beautifully.
A work of pure redneck genius.

Pooh Bear