Gearbox Home at Last!

Good Morning,

I drove to Port Huron MI on Friday and picked up my Auto PSRUs BW350 gearbox and I am very excited to get it out to the hangar. The only thing holding me back from getting the gearbox reinstalled on the engine in my RV-10 is the weather. We have been under siege here in Southwestern Ontario as of late. The snow just keeps coming and coming. The temperatures have been consistently below -10degC during the day and as low as -30degC at night. Not very conclusive for working in an unheated hangar.

Auto PSRUs BW350
BW350 Shipping Container

Here is a photo of the gearbox in the shipping crate. Stuart did a great job of packing it and as such it arrived from Texas unscathed.

My next step is going to be the disassembly of the clutch. When we had the rear seal come out of the gearbox the gear lube was dumped all over the clutch.

Now, most of the oil has had an opportunity to drain away as the aircraft has been inactive for over a year. I just want to be sure that the oil gets out of the clutch disk.

To do that, I need to get it out and then soak it in warm water. After that I think I should ready to put the whole affair back together. I am also going to take this opportunity to go through all of the hardware used in the attachment of the gearbox and engine to the engine mount. I have noticed a number of fasteners that have become rusted over time. I am going to replace all of them with equivalent stainless hardware. I will also replace all of the locking nuts as they have been installed and removed a number of times.

I have to thank Stuart Davis from Auto PSRUs for all of his hard work in getting this gearbox back into running condition. He has walked the walk and talked the talk. He has done the testing and documentation that I have requested and much of the work on his own dime. He has a lot invested in the new company and wanted the investigation into my gearbox failure to come to a definite conclusion. In light of this, I gave him free reign regarding the type and duration of testing.

This resulted in a number of discoveries relating to the design of the lubrication system that we believe led to the input shaft seal becoming unseated from its proper location. The result of this was the cascading failure of the bearings and ultimately the output shaft.

Stuart has communicated his findings to the BW350 owners group and has offered repair solutions for those flying and for new gearboxes being sold. The modification and testing of my gearbox has resulted in it running at a consistent 185-190degF. We are now seeing the constant speed propeller actuation in about 5 seconds compared to 14-15 seconds  previously. We have gone from having a pressure drop across the oil filter of 12-14 psi to a very low 2 psi when using a screen filter.

In addition to these modifications, Stuart has incorporated an internal circlip to retain the input shaft seal and a larger external retainer bracket to keep the output shaft seal in place. He has installed a removable plug that will allow the owner to check the oil level with a dipstick and has moved the breather location from the fill hole to a location higher on the gearbox to eliminate the possibility of the fill/breather hole from being covered by oil. It is thought that this might have caused cyclic pressure build ups that could have assisted in forcing the input shaft seal out.

Lots to say today! Everyone please pray for warmer weather. I want to get my baby back in the air.

Have fun building and flying,



Leave a Reply

Your email address will not be published. Required fields are marked *