Retrofitting VS Governor and PTO to M923

I'm contemplating how I'd like to add a knuckleboom crane to my new M923, and I'm thinking about the PTO and engine speed governor aspects at the moment.

My first inclination would be to add a PTO hydraulic pump to the PTO mount on the transmission. I think I'd like to use an air-shifted one, either by adding an air shift cylinder to an M925 PTO or by picking out a suitable aftermarket PTO. I found this guide from Muncie with some useful background on PTOs:

Understanding Power Take-Off Systems

One of the cranes that I'm considering for my knuckleboom conversion is the Wajax/Palfinger PK19000M from the back end of an MK17 LVS rear body unit (RBU). If I recall correctly, the TMs I found on Scribd indicated that the MK48 front power unit (FPU) supplies about 11 GPM to the crane, so I presume that I'd need to provide a similar flow rate to power similarly-sized crane.

So, would a transmission PTO pump be suitable for this sort of hydraulic flow rate, or would I need to use a transfer-powered PTO like the M936 wreckers use?

I'd also want to govern the engine speed at a suitable constant rate for running the crane. My first inclination would be to retrofit the governor used on the M936 wreckers. I've learned a tiny little bit about those governors from the TMs and searching here on the site. I gather that the "VS governor" on the wreckers has a lever that should be pushed all the way forward or backward to engage/disengage the governor (or maybe vice versa), so it seems like it'd be easy to add on an air cylinder to actuate the lever.

Can any of y'all shed more light on what's involved in retrofitting the wrecker's governor to the existing engine in my M923?

It seems to me that it'd be nice to engage the governor with an air cylinder, too, so that the same dash-mounted control valve would engage the PTO and governor. An interlock with the gear selector and/or parking brake might be a good safety feature, and Mr. Google suggests that there are commercial PTO air shift controls that include air or electrical interlocks to disengage them automatically if the parking brake is turned off, for example.

BTW, I see there's another brand new thread asking similar questions about a deuce knuckleboom installation. I wanted to ask my questions in a separate thread since they involve a different kind of truck/engine/etc.

Any other brainstorming along these lines will also be welcome.

The M939 trucks with front winch have a trans PTO powering a Vickers pump. the stock pump is rated for 14 GPM @ 1200 RPM. In reality the pump is producing close to 25 GPM at wide open throttle. So the answer is yes, the trans PTO is more than capable for running the knuckleboom.

I don't have the numbers in front of me but there are several PTOs commercially available to fit your trans. Get one with a air shift and you are good to go.

You can just use your hand throttle to control engine speed while running the pump. There's really no need to install a governor because the pump won't be very much of a load. The TM for the winch equipped trucks state to just pull the hand throttle to WOT when using the front winch.

Thanks for the information!

I just went through all this installing a lime spreader bed on a M936- http://www.steelsoldiers.com/5-ton-mods-hot-rodding/85285-m936-m936-no-more.html .
Of coarse I used the stock winch pump for my application. I researched the specs for the stock pump and they were more than enough for my needs.

I was even considering getting my hands on a set of the standard winch controls from an M925, but then I decided I'd rather use an air-shifted PTO.

I'm still thinking about putting in a governor, though... I like to over-complicate things.

nf6x, thanks for that Muncie PTO file, it is a good primer for guys like me who only know a little about a few things.

Rick

I'm glad it helps! I don't know very much about PTOs yet, either.

subscribed. I just bought a crane from an mk17a1.

Very nice! I'm interested in seeing pictures of whatever you do with the crane, especially if you mount it on your M936A2. I think I'd prefer the knuckleboom from an MK17 for my project, particularly because of the way its outriggers swing up above frame level for stowage. I'm still curious about the MK17A1 cranes, though. Feel free to threadjack here and/or link to your own crane thread .

I do not have any actual pictures of mine yet, but its a grove crane like the HEMTT's use.