I flew 5 years with a Ross. I've disassembled and inspected 5 or so, just to help out other builders. Just want to offer a different viewpoint based on my findings:

 

First, all of the Ross's have large bearing that absorbs the prop thrust forces. I'm quite puzzled your statement that they don't. A very important part of the installation is to verify you have clearance to flywheel. I'm wondering if you are just confusing the pilot bearing damage issue with prop thrust? Ross redrive had one significant design oversight. This oversight caused around 80% of their field failures. Basically Ross picked a poor method of controlling input shaft clearance. Input shaft is the short shaft that goes between flywheel and gears. Low rpm torsionals caused that shaft to slam back and forth between flywheel and gears. This caused pilot bearing damage, fatigue failures on the drive plate. I changed the design by controlling thrust at the sun gear. All of those failures then disappear.

 

Second, Ross decision to restrict oil flow to redrive is very sound design. It limits flow because excess oil flow to redrive has significant effect on hp loss. A friend actually measured hp loss related to oil volume. I verified flow on my redrive gears & bearings, absolutely no issues. I do believe there were lube issues on some Ross applications, but definitely not true on mine. I don't understand why the difference.

 

 

There is a method of proving design changes that Tracy doesn't use often enough. Basically you measure how close the design is to failure. You don't rely on theory. For example, I verified oil flow just by placing aluminum slivers at key oil locations. Operate drive for a minute, disassemble. Slivers were washed away by oil flow. Likewise, you operate it, then quickly disassemble and measure temperature of various components. A friend slapped a plastic cover on his redrive, then watched the oil flow. These methods let you predict future failures. Too much design theory, not enough actual measurements. If you can force yourself to test your theories, you'll find tons of things you believe in, that just aren't significant.

 

I am in agreement that Tracy version of the Ross design is looking pretty good. When asked by builders which redrive to consider, his gets high marks. I don't have rose colored glasses. There have been a couple design oversights that resulted in failures. I like the solutions.

 

-al  wick

 

 

----- Original Message -----

From: Ed Anderson

To: Rotary motors in aircraft

Sent: Friday, July 31, 2009 3:46 PM

Subject: [FlyRotary] Re: EC2 and Ed's EFISM - a great combination

Actually, George, The RWS drive was not just a redevelopment of the Ross drive.  

 

Tracy basically started from scratch and engineered a redrive that was designed to meet certain objectives while achieving a reasonable cost.   There is no other redrive I am familiar with that has anywhere near the number of flying hours that the RWS redrive has with none of the problems associated with the Ross.

 

While there is a superficial similarly to the Ross (Prop on one end and rotary on the other, planetary gears in the middle {:>)) in appearance, the internals are considerably ahead of anything Ross had.  Pressure lubrication of the prop shaft for one thing, an integral thrust bearing for another, a removable propeller shaft for yet another, full oil pressure lubrication.  The Ross drive required a restrictor in the oil line to (can you believe this) reduce oil pressure – otherwise the thing leaked like crazy – even with the restrictor, the rear seal frequently was a leaky mess.  But, reducing the oil pressure was one reason the Ross had marginal lubrication in my opinion. Even then, the oil distribution inside the Ross was also not well designed.

 

Don’t get me wrong, I was glad to get a Ross – because it was the only thing around at the time.  Had old man, Lou Ross, lived longer he may have eventually fixed a lot of these issues, but unfortunately he did not and I won’t go into the situation with his son, Chris.  But, we are fortunate that Tracy took on this challenge and did it right.  

 

One thing I really appreciate about the RWS design is that it has a considerably different internal set up with easily replaceable parts – which was not the case with the Ross.  If you wanted to completely disassembly a Ross unit you most likely had to take it to a machine shop.

 

Just wanted to make it clear that in my opinion the RWS should not be associated with the Ross unit which many have found shortcomings in.

 

Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm

---

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of George Lendich
Sent: Friday, July 31, 2009 5:20 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: EC2 and Ed's EFISM - a great combination

 

 

Steve,

The Ross drive was redeveloped by Tracy Crook of Real World Solutions (RWS). Tracy now uses the 6 planet planetary (Ford Unit) and is about the best you will get  weight wise and value for money.

 

There are other similar units - all have slightly different construction, however Tracy's is well proven. I will probably make my own, but only because of the tyranny of distance and associated costs.

George (down under).

 

Steve,

I went with the RD-1B PSRU from RWS.

 

T Mann

__________ Information from ESET NOD32 Antivirus, version of virus signature database 3267 (20080714) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com