Relocate Oil Reservoir to Prevent Hydraulic Oil Lock 912 Model 3

[atosrider]

Has anyone relocated the oil tank to have it lower, and less likely to cause hydraulic lock? There is enough room on the people side of the firewall, where the header tank used to be.

Have other owners with early 912 installations experienced hydraulic lock?

I just went through the hydraulic lock recovery process on my other ultralight. It too has the oil tank bottom at the upper design limit of about equal to the crankshaft / oil pump. Hydraulic lock was never an issue, until I dismantled the plane for ground transport. During disassembly the fuselage was on a slope, which must have been enough to start the syphoning. Not what you would want to happen anywhere else than your home base.

So as I rebuild this model 3, why not add a few more weeks to design and fabricate yet another better way of doing things? <many times I envy the new kit builders>

If the oil tank moves behind the firewall, there will be a huge open cavity over the motor, as I have scrapped the hot air box in favour of heat probes in the carburettors. mmmmm, will that mess with the air cooled cylinders?

[Dusty]

I would recommend leaving the tank in the stock position as access for checking is good. If you are getting hydraulic lock there may be a problem somewhere else, possibly non standard filter? Keeping the oil lines short is more of a priority as the oil feed is mainly suction. 5 years with my current fox I haven't experienced a hydraulic lock yet.

[Av8r3400]

X2 what Dusty said.

I've been flying 912 powered model 4s for over 10 years and have yet to have a hydraulic lock situation. Rotax filters have a check valve in them that prevents this problem.

[jrthomas]

I agree with Dusty and av8r3400. It's not worth the effort. Hydraulic lock doesn't happen unless your plane sits for months at a time. I completed my model 4 late 2015 and I've never had a problem. I just pull the prop through by hand for a few turns if I'm not able to fly.

[atosrider]

Good to hear of no problems with the model 3 layout. I don't want to fix a problem I won't have!
On my other ultralight it has the official oil filter, but it never sat for a 16 months without turning a prop. It was only supposed to be 4 or 5 months, covid made it another year.
oops, did I start another debate - how to store a 912.

thanks for the comments

[Eric Page]

There's also the issue of putting oil through the firewall. A leak of hot engine oil onto your feet and lower legs in flight would be catastrophic. The tank would also be a significant and uncontrollable source of heat in the cabin. That might be nice in the winter, but not so much in the summer.