REFLECTOR: Franklin Accessory Gears

[Laurence Coen]

John,

That gear is what is known as a helical cut gear and should not produce end 
thrust.  There was an AD issued for Franklin engines that warned against 
using American made gears mating with PZL built gears or visa-versa.  Since 
your gears need replacing that could be the real problem.   The US built 
gears were made from cast iron blanks and the PZL were steel.  They were 
also machined on different gear cutting machines.

Larry Coen
N136LC

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From: "John Dibble" <aminetech at bluefrog.com>
Sent: Saturday, April 28, 2012 1:32 PM
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Subject: Re: REFLECTOR: Franklin Accessory Gears

> On 4/28/2012 10:45 AM, Laurence Coen wrote:
>> John,
>>
>> There shouldn't be wear between the gear and the housing under normal 
>> circumstances.
> Are you saying that the gear should not touch the housing?  Mine does and 
> the bevel of the gear forces the gear against the housing making wear 
> inevitable.
>
>>   Check for proper alignment of the alternator and the drive pulley.  I 
>> think that bronze is the proper material to use for a shim.  If the 
>> bronze wears down you have to replace the shim.  If you use steel and the 
>> shim spins with the shaft the housing will wear.  Replace the shim or 
>> replace the housing? Your choice.  Think of the crank which is steel and 
>> is supported by soft bearing material.
>
> That's the other area I'm concerned about.  I'm hoping the metal analysis 
> will indicate if the bearings are wearing.
>>   Any wear that takes place is of the bearing not the crank.
>>
>> Larry Coen
>> N136LC
>>
>> --------------------------------------------------
>> From: "John Dibble" <aminetech at bluefrog.com>
>> Sent: Friday, April 27, 2012 5:47 PM
>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>> Subject: REFLECTOR: Franklin Accessory Gears
>>
>>> During my last oil change I got a big surprise, finding a lot of metal 
>>> on my ADC oil filter screen.  This is a great filter and lets me see 
>>> everything that's filtered from my oil. A magnet indicates that it is 
>>> mostly steel.  There are shiny aluminum particles also.  My Franklin 
>>> mechanic told me that the gears are the most likely problem, so I have 
>>> removed them.  A local mechanic told me that the gears need replacing. 
>>> He checked the cam and that looks good.  I sent the metal from the 
>>> filter for analysis so I can make a final determination if I need to 
>>> look for any thing else.  I took apart the alternator gear and there is 
>>> wear between the gear and the housing.  I want to install a shim washer 
>>> between the gear and the housing.  Bronze was suggested, but after 
>>> seeing the wear, I think bronze will get eaten up fast, so I'm thinking 
>>> of mild steel.  Any comments or ideas will be appreciated.
>>>
>>> John
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>
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