Thanks everyone for your input.
In real life the metal also has a blue tint, so heat is definitely a factor.
It's not a VFD. The pump hangs off a PTO which is mounted to an Allison transmission with a heavy duty diesel engine as the prime mover.
In a different thread we did an analysis of...
As promised, here's an album of the wear on the internal splines of the PTO: https://picasaweb.google.com/dmb2000/ChelseaSplines?authkey=Gv1sRgCNznvcufhd3hJQ
Thanks,
David
It's puny! :) Again, thanks for your help Ron. Now I know why they don't last. I can move to the SAE BB shaft (1"-15T) and that will give me:
1) a 'compressive stress in teeth' margin-of-safety of 0.349 versus -0.129, and
2) a 'shear stress in teeth' margin-of-safety of 0.487 versus -0.032...
Ted,
Attached is a chart showing pressure, rpm, and flow requirements.
Thanks,
Davidhttp://files.engineering.com/getfile.aspx?folder=14c84bbf-9d1f-44ab-b89b-e3df6fecc71c&file=HP_and_GPH_PTO_Pump_Requirements.JPG
Hi Ron,
You're correct. After paying special attention to the correction factors in your spreadsheet (at zakgear.com) it appears that the compressive stress of the SAE 'B' shaft is on the edge.
I have the following factors:
Application Factor, Ka, 2.2: (driven by diesel engine, light shock)...
Thanks swall,
I notice that when looking at a spline tooth in the radial direction, the wear is curved; i.e., there's more wear in the center then the ends - the center is knife edge while the ends still have machine marks on the top edge of the tooth. Is this fretting or load imbalance or...
Folks,
Here's a photo album of the splined shaft from my hydraulic pump. The interior splines of the mating PTO are identically worn.
I'm in the process of identifying the steel, but I believe it to be a high tensile steel (4140 or 4340). My apologies for not being able to narrow this down...
Thanks Ted and Ron,
Ron, I used your link to check my numbers and they do checkout, but these are steady state conditions. There may be transient conditions which likely push the compressive stress well beyond my 6K psi steady state.
The pto is constant mesh, so the pump is always spinning. A...
Thanks Ron,
The pump external shaft uses DU bushing journals, one on either side of the pump gear, width: 1.125" x ID: 1.30".
The PTO helical shaft is supported on cone bearings with a lock ring. It's an SAE 'B' shaft. I don't know the bearing dimensions. The shaft is 1.25" OD, and the...
Here's a photo album of the cleaned up external spline.
https://picasaweb.google.com/dmb2000/PTOPumpSplines?authuser=0&authkey=Gv1sRgCNSloqW9qonCaQ&feat=directlink
Thanks,
David
hydtools and Tmoose, thanks for your help. Avoiding idle is a possibility. Thanks for the tip on Kluber spline grease. I still haven't had a chance to take new photos of the cleaned up worn splines but hopefully today or tomorrow.
Thanks,
David
The manufacturer of the PTO says that the wear is caused by engine idle time.
The application is a hydraulically driven fan motor. The fan produces a variable load on the pump. The fan control is proportionally driven and the fan motor has built-in trim speed control.
There are 5 components...
Thanks Ron, I'll produce a better picture, in the meantime attached is a slightly cleaner photo of the PTO internal splines.
Thanks,
Davidhttp://files.engineering.com/getfile.aspx?folder=843abcf9-7d23-4765-8822-99d4238d0e62&file=PTO_Shaft.JPG
I have a hydraulic pump with a 7/8"-16/32DP straight involute external HT alloy steel spline shaft. The splines are experiencing contact fretting. (See spec's below and pic attached). The pump connects to internal splines of a constant mesh PTO, which in turn is bolted to a truck transmission...
