Trying to make a gear pump

[Futterama]

Hi forum,

I'm new here but have been reading alot about your fine projects.

I have a small lathe and a small vertical mill and wanted to build a gear pump, later some valves and cylinders, just for fun and maybe it will end up with a wheel loader build of some sort.

Anyways, I have these module 1 10T gears I want to use for the gear pump. The flange section has to go for the gear to be used in a pump. Now how do I fasten the gear to the axle without the flange to drill and tap for a set screw?

The gear has a 4mm hole, the axle is a 4mm surface hardened pin.

Please advise :-)

Thanks.

Best regards,
Martin from Denmark

[Futterama]

Okay then. Lots of views but no replies.

I have changed tactics. I'm going to get a gear cutter and cut my own gear so the axle and gear is made from one piece. I have a few questions regarding gear pumps and I'll see if someone here can answer.

How does the following parameters affect the pump characteristics?

1. Number of gear teeth.
2. Gear width.
3. Teeth size (e.g. module 1 vs. module 2).

My idea of the parameters above are:

1. Low number of teeth: Low flow, high pressure. High number of teeth: Higher flow, lower pressure due to the increased load on the motor driving the pump.

2. Narrow gears: Low flow. Wide gears: Higher flow, increased motor load.

3. Small teeth: Low flow, high speed motor. Bigger teeth: Higher flow, lower speed motor.

The gear pumps I have seen around the internet, always have few teeth, around 10, which is AFAIK the smallest gear in the module system, and the gear width is somewhere around the same as the gear diameter.
Any particular reason for this?

If I was to make a hydraulic gear motor, would bigger gears be an advantage to get more torque or does the bigger gears have a negative impact on performance due to the changed angle at which the gears mesh?

[ihbuilder]

take off the hub then turn (lathe) a shaft so that you can press fit the gear to the shaft . what materials are you using ?

[civic83]

could you braze or solder the gears to the shaft?

[Futterama]

Yeah, maybe press fit is the only way, I just like that the cylinder pin is surface hardened and probably more smooth and straight than I can make with my lathe.

The gear on the picture is 11SMnPb30 / C45 steel and the pin is some surface hardened steel (so hard you cannot machine is with HSS).

Brazing could be an option if a suitable filler for steel could be found, I've never tried it or seen it done.

[JAMMER]

The easy way to press fit it is to have a shaft that is just larger than the hole in the gear then heat the shaft and put the gear in the freezer for a while and they should go together and you should not need a keyway this is called sweat fit and works great. Ed

[Trackerman]

Ed,
" just larger than the hole in the gear then heat the shaft and put the gear in the freezer for a while and they should go together " you mean the other way around don't you? freeze the shaft to shrink and heat the gear to expand, gear slips on shaft and the shaft heats and expands locking the gear in place.

cheers

Paul