The International Cessna^® 170 Association

I have a Whelen rotating beacon p/n 0700120-1 mounted on top of my fuselage. Surprisingly it still works. I disassembled it to see if there was any preventative maintenance that I could do so that it would keep working. It all looks quite sealed--I didn't see any obvious places to lubricate. Later, in researching documentation on the beacon, I found a flyer from Whelen which says "Maintenance: Periodic inspection of fittings, bulb, lens and dome. No lubrication required." Back in the '60s Cessna or Whelen must have had some problems with this unit - especially the bulb - as there were several Service Letters issued on it. SL62-17, SL62-77, SL63-60, and SL66-22 all announced improvements made to components of the beacon. SL66-22, a page of which is shown below, adds a new diode to the motor to "eliminate 'spike voltages' from adversely affecting the electronics of the motor and premature burn-out of the bulbs." So here's my question: My rotating beacon doesn't have this diode (Sarkes-Tarzian p/n 2VR18) added. Is this a solution looking for a problem? After all the beacon seems to have been working for the last 40+ years without the diode. If it will help in extending the life of the beacon motor and bulb, what would be an acceptable substitute p/n for this diode?

All that diode is doing is preventing a collapsing flux-field from surging backwards through the unit when the beacon or the aircraft master is turned on/off. Pay attention to the drawing to place the diode in the correct polarity. (See that "band" at one end of the diode?)
A good subtitute is Radio Shack 1N4005, cost 99-cents. (1-Amp, 600 PIV)
http://www.radioshack.com/product/index ... Id=2049728

n2582d wrote:Is this a solution looking for a problem? After all the beacon seems to have been working for the last 40+ years without the diode. If it will help in extending the life of the beacon motor and bulb, what would be an acceptable substitute p/n for this diode?

Using a diode like this is also a good idea on your master and starter solinoids and would probalbly negate the need to put one on your beacon since it would protect your whole electrical system.

n2582d wrote:I have a Whelen rotating beacon p/n 0700120-1 mounted on top of my fuselage. Surprisingly it still works.

If after 40 years it ant broke....why fix it?

The most likely things to fail are the motor brushes and bearings. I've repaired many electric motors with brushes purchased at the local ACE or True VAlue hardware store, from their repair-parts for electric drills, saws, etc., bins. The bearings are usually sintered-bronze and a drop of motor oil on them anytime they are opened up will extend their lives.

(The electric motors in my Baron's cowl-flap motors were back-ordered and $2400 EACH from Beech. I rebuilt mine with brushes for a Makita hand-drill, which were a near-perfect fit. (I had to shave them slightly thinner using the side of the wheel on my bench-grinder.) Those cowl-flap actuators are still in service 8 years later. Total cost: $3.95 and an hour-and-a-half of rewarding labor. I rationalized they were "owner-produced" parts.

Thanks for the responses.

Service Letter 62-77 says, "present parts catalogs do not show the motor assembly as a separate spares replacement item; however, it is now available from the Cessna Parts Department - - the Part Number is WRM-39 and is priced $20.70." I tried the standard Cessna parts look up websites and couldn't find it. Aircraft Spruce does have a couple of other spare parts for the beacon. http://www.aircraftspruce.com/catalog/e ... beacon.php

Whenever I've had difficulty with the Cessna websites, I've called and talked to the parts guys at Hill and/or Yingling and found them knowledgeable, and have usually found the part.

I have a Grimes rotating beacon I'm presently going through, and it looks like other than cleaning and lubrication the only thing I need is a new contact for the arm which provides the power for the lamps. I'll try to post a picture of it later but the arm is basically a spring with what looks like it used to be a graphite pad on the end of it for a contact, which sets down on the rotating post on the center of the gear wheel the lamps are attached to. I've looked at some old tractor points at the auto parts store but they look to flimsy, even if I could get them off the point arm they would probably break when I tried to attach them to the beacon contact arm. Anybody have any suggestions for a source on these contacts? I can't seem to find any parts for these Grimes beacons online.

That's not graphite. That's a carbon brush. Similar set-ups are found inside distributor-caps, etc. Have you contacted the mfr'r?
Here's another possibility, but for not much more you can replace it with a Whelan strobe:

http://www.aircraftpartsandsalvage.com/ ... ing+Beacon

I couldn't find anything on Grimes, I assumed they were out of business. I'll look into the distributor cap idea.

Oh Oh, found them now. My bad, I kept digging under grimes rotating beacon, I found them with grimes mfg.

Surprisingly it still works. I disassembled it to see if there was any preventative maintenance that I could do so that it would keep working.

ROFL! Nothing good can come of this!