How To Remove The Drive Pulley On The
QCU Propeller Speed Reduction Unit (PSRU)
By: George Hurt
On the QCU Propeller Speed Reduction Unit (PSRU), or redrive, the drive pulley is attached to the crankshaft on a tapered shaft. The shaft is steel, the pulley is aluminum and once the pulley is installed it is hard to remove. This assembled interface between the two components is so positive that it does not require any kind of key to lock the two together.
The only way to remove this drive pulley without totally destroying it is to use proper tools. The attached photo shows a 'split plate bearing puller' which is the proper tool to use to remove this pulley. This type of puller does not work on the new style drive pulley with the starter ring gear attached. A different puller is required for that and will be illustrated later in this article.
Removal of the pulley takes a lot of pressure and when the attachment releases it does so with a BANG! and a lot of energy is suddenly released. This can cause the puller and parts to fly about, so if you are doing this while the engine is on the aircraft be sure that you have the puller and parts secured in some suitable manner. I use some type of overhead bar, board or beam and loosely tie all the pieces overhead with a small rope. Then when it all comes apart the parts do not hit anything and cause possible damage.
A good puller set up as described in this article is rather expensive for occasional use but can be rented reasonably from most rental stores.
A split plate bearing puller cannot be used to pull the bottom QCU drive pulley when it has the QCU starter ring gear attached because the drive tower cannot be removed without first removing the pulley.
The illustration above shows the type of puller needed to pull the bottom pulley with the ring gear. This type of puller will also pull the bottom pulley without the ring gear and with the tower removed but is rather hard on the aluminum pulley and may mar it. This tool may be rented from various rental centers as well.