flyrotary@lancaironline.net Mailing List Archive

Hi Marc: I purchased Dennis’s 7A the end of last Sept. and now have about 5.6 hrs. total hrs. getting to know it. I visited Dennis in 2023 and at that time he was down for both the described PSRU issue and an intermittent EC2. Dennis worked on the EC2 and he told me that in looking for the “gremlins” that had caused the intermittent issues, the engine had “backfired” a few times rather violently, and he believed that is what ultimately caused the pin on his PSRU to fail.

Dennis mentioned the pin had sheared and the shaft then spun about 3/32ds, and that is visible here. While working at Langley AFB from 2020-22 I heard about Pat Parker who had been building a 7A with RX-7, and was calling it quits and gonna send stuff to the dump so I purchased TECH Welding RADs, a spare 13B, EC2, EM2, prop/spinner and most importantly a zero time “C” Model PSRU. I already had a spare “A” model (Bernie Kerr flew it in his 9A) which is what my 9A is using, so I gave Dennis a good deal on my “spare” “C” model, so he could get flying again. He installed that and started doing some ground runs and everything was running well, but he decided to sell his a/c and listed it on Trade a Plane (w/out the engine), and he graciously offered it to me “with” the FWF still attached, so I purchased that the end of Sept. Since it hadn’t flow in over 1.5 yrs.; I worked on it for two months and performed a first flight in my local area in early January, and have since put another couple hrs. on it until life got in the way a bit.

Anyways, that’s how Dennis solved his PSRU issue…swap out the input shaft and gears with a zero time unit. :)

Doug

767TX RV-7A / RX-8 13B 932 hrs.

????? RV-9A/RX-7 13B 4.2 hrs ground run time :)

Dennis,

How did you end up fixing this, and was it a RD-1C redrive? Contrats on 920 hours on your rotary engine! Is it a series 1 or 2 rx8 engine?

Marc

From: Rotary motors in aircraft
Sent: Monday, November 27, 2023 9:09 PM
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: RD-C input shaft failure

The shaft between the RX-8 engine and the reduction drive unit has a gear secured to the shaft with a steel pin. (The gear drives the planetary gear set). The steel pin sheared off allowing the gear to rotate on the shaft. I understand this has happened to others in the past. I’ve heard that several fixes were proposed or tried – welding the pin to the gear, doing more deforming of the pin at the gear surface or installing a tighter or larger pin. I have another new shaft/gear assembly I plan to install after I incorporate improvements.

When the pin sheared the gear only rotated about 3/32 inch on the shaft. The two pieces of the pin outside the shaft were thrown out of the gear and apparently were chewed into very small particles by the planetary gear assembly.

Any info. You may have will be highly appreciated!

I have about 920 hours on my RX-8 engine in my RV-7A

Dennis Haverlah

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