35 Amp Generator

[wa4jr]

I am down here in San Antonio for vacation and to deliver my wife to her mathematics conference. Flew down in our 170B after a $4500 annual to catch up on years of pencil whipping paper annuals. Had a gen shaft leak prior to annual so I took the gen off and had it opened up. My IA found the O ring split in two, and so we replaced it. IA did not think the shaft seal was leaking since it was still "pliable". During the flight down from VA to TX, I noticed an increasing oil leak. Landing at Stinson Municipal in San Antonio, I got out to see oil not only dripping from the engine area, but also from the tailwheel....not good...especially after shelling out so much money from my rear opening for the "mother of all annuals". Upon taking the gen apart again, the newly installed O-ring is badly damaged where it rides along the woodruff key area. How can O-ring damage be prevented so that this problem does not happen again. I asked the shop to apply some orange or gold RTV to the new seal so as to completely fill the sealing cavity and ensure a good seal even if the O-ring is damaged upon installation. I am also replacing the shaft seal even though it was still "pliable". In my experience, even if the seal is still pliable, once the sealing "lip" is worn down, a leak can develop...and then there is the possibility of scoring.

I'll be down here at Stinson Municipal at Stinson Aviation if anyone wants to drop by and shake my oily hand! Maybe you can come by and convince me that I AM on vacation and that it is possible to get these 35 amp gens to seal. After not thinking about an alternator conversion, I am thinking about one just to get rid of the fiddly little oil seals of the factory generator.

Thoughts and ideas to help me dry my generator up?

[zero.one.victor]

Don't be thinkin' that an alternator never leaks oil! My ragwing has a 60-amp alternator,which has an oil leak I was unable to eliminate. It leaks along the shaft &/or shaft bushing back into the aircooled area of the alternator,then drips out onto the top of the oil filter adapter. For a while I thought the adapter was the source of the leak,as I had just had the alternator rebuilt by a local auto-electric shop (mistake!). I was able to reduce the amount of leakage by siliconing the shaft/bushing junction in question,then reassembling.
Since I was able to greatly reduce the leak,now I just wipe off any oil in that area when I check the oil level during my preflight & it never gets onto the belly or firewall.
I think the 60 amp alternator is bigger and probably heavier than the 35A generator,and it's greater capacity is probably overkill for the needs of most of us--I know it is for mine! I would just as soon have the 35A generator back.

Eric

[Koop]

One good thing about my 170 b, is the lowly 20 amp. Gen. It does not leak, knock on wood! koop

[GAHorn]

The 170 Book, page 94 contains an article about this issue. Several generator models can be fitted to the engine other than the original 1101898 Delco, which may have this problem. (That's the original 35A gen. 1101897 is the 25A, 1101890 is the 20A, and 1101876 is the 12A.)
The generator drives differ on several models that also can be mounted on this engine in ways not depicted in the overhaul manual.
The fix, on those with O-rings and woodruff keys is to grind/file the end of the key smooth so that it doesn't destroy the O-ring. TCM doesn't approve of this, but it's been done on many gens that have that type drive. "Ray" at Sacramento Sky Ranch has apparently been helpful to those whove contacted him about this.
Remember my own oil leak problems last year at the LAS convention. That generator mount gasket must be replaced entirely, without cutting or modification. This also means the tach drive housing seal must be replaced, for the same reason you never want to re-use a seal (including the one you're telling them not to save, John.)
And, Oh Yeah! Remember that that seal has it's open end face the engine,...not the generator. Sometimes even knowlegeable overhaul people do this backwards. Remember, you're tying to keep the oil in the engine!! Even though pliable, they take a "set" and will likely leak. The seals are cheap...less than a couple of bucks, and very irritating if it leaks after spending all that time and labor.
RTV is never a good idea inside an engine or accessory that is submerged in oil. RTV is not oil-proof, and it will break down into particles and go visiting throughout your engine,...sometimes with damaging results.
An alternator is not a fix for this problem. The fix is using the correct part numbers and installing them correctly with correct materials. (Permatex is permissible on the gaskets.)

[zero.one.victor]

RTV: the first time I changed the oil of my 170,I found a long strip (about 3" by 1/16") of orange/red RTV caught in the pressure screen. I don't know where it came from,& I never saw any of it there again,but it sure was a surprise! So who sez those screens never catch anything?

Eric

[wa4jr]

Thanks for the pointer on the woodruff key George. I didn't get the message until after my generator was rebuilt at Navajo here in SAT. I put the unit back on Wednesday afternoon. I used the original gasket as it was new 10 hours ago and was a combo tach drive/gen gasket. The gasket was not stuck to the accesory case so I gently lifted it up and cleaned both sides as well as the case face. Ground ran the engine and although the gen no longer leaked....I saw oil coming out of the crush washer between the case and oil filter head. The filter head had been removed, cleaned and reinstalled to accomodate the larger 48109 filter. Check Six at Stinson gave me the crush washers but before I took the head apart and spilled the rest of my oil, I just tried cutting away the safety wire and re-torqueing the filter head. After several tries...being careful not to pull the threads out of the accessory case, I was successful in getting the crush washer to seal and ended my leak A test flight yesterday down to Pleasanton and back revealed the gen and filter head free from leaks and we are ready to start back to Virginia on Saturday afternoon! Guess I will keep my generator a bit longer...the repair shops seem to have fun with them when they come in as they just don't see many of them anymore! Thanks again for the tips.

[GAHorn]

Yeah, and with a generator, if you leave the master on and kill your battery, you can still prop it and it will recharge the battery. With an alternator, you must either remove the battery and recharge it, or you must "jump" start it, and leave the starting battery connected long enough to close the charging circuit.... A sometimes dangerous task with whirling meat-cleavers nearby.

[zero.one.victor]

I don't mean to start anything,but that filter adapter (if it's an El Reno/F&M) is STC approved to use the 48108 filter. It's probably ot especially legal to use a different one.
Why did you want the larger filter?
Also,be advised that at least some of the alternators out there (like mine) need to be relieved a little with a grinder for the filter adapter to clear.

Eric

[GAHorn]

That's an excellent point, Eric. The longer filter has greater "moment" during normal engine vibration and poses a greater stress on the mount, the accessory case, and the fastners, subjecting them to greater liklihood of failure. This was one of the criteria examined in obtaining the STC. The STC for the El Reno/FM Enterprises adaptor for the C145/O300 specifies the 48108.

[wa4jr]

I asked my AI the same exact question. Seeing the longer filter I envisioned it putting more stress on the filter head as the engine vibrates in it's mounts. My AI did not seem worried at all, but if the STC for the El Reno filter head adapter indeed specifies a 48108, I will be going back to it. I'll check my MX records for the STC on this topic.

[Dave Clark]

I had a hard enough time keeping that adaptor leak free so I'd stick with the short one. Better yet change to a Firewall mounted one.

[GAHorn]

The early FM-Enterprises/El Reno adaptors used a different mounting gasket and chamfer that was sometimes leak-prone. FM will modify your early adaptor to the later standard free if you send it to them. They will also loan the correct thread clean-out tool necessary to acheive the proper torque for installation to prevent leaks.
http://www.fm-enterprises.com/mainmenu.html
The chief advantage of the FM Enterprises adaptor is that there are no hoses to maintain or leak, and no stress or holes are applied to the firewall. A drawback may be clearance with an alternator conversion. Minor modification of the alternator case by grinding/re-positioning may be necessary.

[David Laseter]

You're not going believe this!
While I'm at work, my local maintenance shop has been doing an annual on my plane. The annual went real well and they were impressed with how well preserved it is. Anyway I asked them to stop the oil drips, which I figured were coming from the new generator I installed last fall. Today they told me the leaks are stopped and that they had replaced the generator gasket. NEXT QUESTION (easy George) Ya'll used a one piece generator/ tach gasket right? Well actually the Tach part was good, so we put a new round gasket around the generator and trimmed the tach part back. So, your saying there is a split in the gasket between the gen & tach? yep! So we've had this big discussion and he assures me it will be fine. He's a friend and plans on flying with me in the regular future.

* Could I try it for a while, checking after every flight for leaks, until next annual OR

* Should I just order the gasket now and take the plane right back down there and tell them it's got to be done with a one piece gasket?

[GAHorn]

Ask them where they got the approved data to modify that part number gasket. (There's a reason that gasket is one-piece. What's their authority and reason to defeat the purpose?)
I've already told everyone what happened three times with my gasket so modified, so I won't take you all back through it again.
Change the gasket, intact, and also the garlock seal within the tach drive housing.

[zero.one.victor]

I recently replaced just the generator portion of said gasket myself. Maybe it's not strictly according to Hoyle,but suffered no apparent problems. What trouble did you have with doing that,George?

Eric