Does anyone know of a hydraulic mule that could be used for gear swings on twin cessnas? Or has anyone ever built one? The MX manual calls for this thing but I can't find much on it.

I built one for my 210 years ago. I bought most of the parts from Northern Hydraulic and used an old pressure washer motor for power. I only have a couple of hundred bucks in it. It has variable flow and works great. I’ll try to find a picture of it next week and post.

Northern tool sells hydraulic units, similar to what would be used on hydraulic bi-fold doors, for a few hundred bucks. They will effortlessly swing the gear on piston planes.

The BEST way to ground run the hydro system is to use an electric motor to run the pump WITHOUT opening the system.

That's what I do on trailing link twin Cessnas.

Here's the pro solution: https://pilotjohn.com/new/dehaut/robomule-5000

But mine is home brewed.

Hi Michael,

That idea is great. I love how you can just spin the ship's pump without breaking any lines. But I don't think you'd be able to pull the pump out far enough from behind the accessory case to fit it to an electric motor. I don't know that the lines are long enough, at least on a conquest. That works on a 421?

Scott

Indeed, the 425 lines are too short and stiff to get proper access, so you will need to hook-up extension hoses to get access to the drive on the pump .

And you're right: on the 421 there is more room and hoses are longer & more flexible allowing direct hook-up.

I know nothing about this. I saw this video once and easily found it with a google search. It may and may not be helpful.

Best

https://m.youtube.com/watch?v=w67UYBa48Lg

[youtube]https://youtu.be/w67UYBa48Lg[/youtube]

I built a mule for my T210, here's how I did it:

I sized the gpm and max working pressure to match my engine-driven pump. In my case, that turned out to be quite a bit more than cheap harbor freight type power units put out.

I found a Parker D-Pak hydraulic power unit was a good match for the onboard pump. I found a lightly used one on eBay with a high-pressure (output side) filter cartrige as well as suction-side filters. This is important, you don't want to push FOD into your system from the pump. It cleaned up well, I replaced all the filters and changed the fluids, cleaned out the reservoir, etc. I set the pressure relief valve to the max pressure in the Cessna manual (the secondary pressure relief valve setting in the power pack).

The local hydraulic power shop made me a pair of 25' hoses, that's way longer than needed but I like not having the cart right under the airplane. I had them use quick-coupling fittings and assemble them with opposite genders, so that I can't mistakenly switch the return line for the supply line. The shop was happy to pressure test their hoses. I used only crimped-on fittings. (Just tell the shop your working pressure and they'll select the right hoses and fittings etc)

It works great, it swings the gear at the same speed as inflight.

Quirks of my setup: I also run a tube from the firewall overflow tube to the mule's reservoir. I had to add a 3-phase converter because my hangar only has single-phase AC power. I plug the hoses into eachother (male to female quick coupler) to keep the system closed when I'm not using it. (I am somewhat strident about cleanliness in hydraulic systems) I put a ball valve (shutoff) on the pressure hose, but not on the return hose to the mule.

Ask an expert, they'll steer you away from the eBay and Harbor Freight type of cheap hydraulic pump. It doesn't take much FOD (such as shavings from the pump gears scraping the pump housing) to harm your airplane's hydraulic system, and those units probably don't run at the same gpm while making the same pressure as your onboard pump.

Picked this one up for a certain BTr who got it from a surplus auction for .01c (literally one cent).
Japanese unit in perfect shape with 16 hours on it.

Perhaps overkill and needs 400v 3 phase but would do the job lol.
Conveniently it was at a facility a mile from my office at KDVT.

Man, don't Cessna high wing retract gear swings on jacks make ya nervous...

Ain't that the truth. I have to jack my Cardinal 20" off the ground to get the gear to swing. And the Cardinal is about 2" too short to get the heavy duty jacks under the wing.

Vince

Here are a couple of pics of my mule for my 210. The black valve with the knob on it is a needle valve to regulate flow. I had the best luck plumbing it into the return from the pressure regulator. That way when I open it up, it lets the pump run unloaded. That keeps the oil a lot cooler that it would be if running with pressure built up all the time. I first tried installing it on the output hose but the 5606 got hot really quickly.

Wait till after the election they will be lying around everywhere.

Actually, Cessna high wing gear retractions (and extensions) makes me nervous, always. Jacks or airborne.