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07-28-2017, 10:09 AM
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Join Date: Jan 2016
Location: Prior Lake, MN
Posts: 30
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Tach drive delete?
So quick trip to Oshkosh and new Lycoming cylinders are ordered, getting serious about assembling an 0-360. I wanted to check with engine experts here on the current thoughts of deleting the tach drive during engine assembly. Reading through previous posts I have noticed cons with both approaches.
1. Engine destroyed because tach drive was operating unloaded and failed.
2 Engine destroyed because I removed the tach drive and all the oil departed the breather line.
Hoping for more encouraging advice that does not result in engine destruction.
-Bruce 
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07-28-2017, 10:25 AM
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Join Date: Jan 2006
Posts: 307
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Bruce, install the drive gear assemble. There is no downside to installing it.
If you delete it please report your findings.
__________________
Tad Stripes Sargent
GRT HXr Glass
TITAN POWERED IO-370
Hartzell's advanced composite propeller
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07-28-2017, 10:44 AM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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Reassembly of my 540 saw me delete not only the tach drive shaft, but one magneto idler gear and shaft assembly, swapped the fuel pump eccentric idler with the just deleted idler gear, deleted the fuel pump pushrod, and the vacuum pump drive gear, shaft and housing.
One needs to evaluate oil flow when eliminating parts in the accessory case. Many (like the idler gear and vaccum pump drive) are integral to the pressure lubrication path. Many people pull the vaccum pump shaft and leave the housing, not realizing they have just created a massive internal oil leak.
Its great to reduce rotating mass, but think it through before you start deleting stuff.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
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Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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07-28-2017, 10:58 AM
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Join Date: Jan 2016
Location: Prior Lake, MN
Posts: 30
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I appreciate the thoughts and your experience. Looking at the accessory case there is not an oil path feeding the tach drive, looks to be splash lubrication. In this case there will not be a massive internal oil leak causing low oil pressure.
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07-28-2017, 11:40 AM
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Join Date: Jan 2005
Location: NC25
Posts: 3,508
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Quote:
Originally Posted by tadsargent
Bruce, install the drive gear assemble. There is no downside to installing it.
If you delete it please report your findings.
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Correct!
Have had mine for 20-years and more than 3,000 flight hours.
__________________
Gary A. Sobek
NC25 RV-6 Flying
3,400+ hours
Where is N157GS
Building RV-8 S/N: 80012
To most people, the sky is the limit.
To those who love aviation, the sky is home.
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07-28-2017, 02:10 PM
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Join Date: Jun 2007
Location: new iberia la
Posts: 768
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Tach drive
After some back & forth email with our very own Lyc guru Mahlon I left mine out.
Don Broussard
RV9 Rebuild in Progress
57 Pacer
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07-28-2017, 08:45 PM
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Join Date: Mar 2015
Location: Aurora
Posts: 81
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Quote:
Originally Posted by Toobuilder
Reassembly of my 540 saw me delete not only the tach drive shaft, but one magneto idler gear and shaft assembly, swapped the fuel pump eccentric idler with the just deleted idler gear, deleted the fuel pump pushrod, and the vacuum pump drive gear, shaft and housing.
One needs to evaluate oil flow when eliminating parts in the accessory case. Many (like the idler gear and vaccum pump drive) are integral to the pressure lubrication path. Many people pull the vaccum pump shaft and leave the housing, not realizing they have just created a massive internal oil leak.
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As an EFII user I am doing something similar to my 540. I had planned to leave out the mag drive gears, the tach drive gear, vac drive, and of course the fuel pump plunger. You're saying the vac drive shaft is crucial to moving oil to all the other gears?
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07-28-2017, 09:21 PM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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Quote:
Originally Posted by stringfellow
As an EFII user I am doing something similar to my 540. I had planned to leave out the mag drive gears, the tach drive gear, vac drive, and of course the fuel pump plunger. You're saying the vac drive shaft is crucial to moving oil to all the other gears?
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Depends on the gasket used. If you use the "cover plate" gasket which blocks the oil port at the accessory case then you are golden. I'm guessing you will delete the vac drive extension and just install a cover plate directly on the accy case which makes the gasket use moot. Where people run into trouble is removing the shaft, but leaving the extension. This leaves the 1/8 inch oil supply port to the shaft wide open and makes a massive internal leak. Block that leak with the gasket or a blank cover and you are fine.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
Last edited by Toobuilder : 07-28-2017 at 09:29 PM.
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07-29-2017, 03:55 PM
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Join Date: Mar 2015
Location: Aurora
Posts: 81
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Quote:
Originally Posted by Toobuilder
Depends on the gasket used. If you use the "cover plate" gasket which blocks the oil port at the accessory case then you are golden. I'm guessing you will delete the vac drive extension and just install a cover plate directly on the accy case which makes the gasket use moot. Where people run into trouble is removing the shaft, but leaving the extension. This leaves the 1/8 inch oil supply port to the shaft wide open and makes a massive internal leak. Block that leak with the gasket or a blank cover and you are fine.
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Thank you. Always worried about stuff like this that falls into the "i don't know what I don't know" category.
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07-30-2017, 03:22 PM
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Join Date: Aug 2015
Location: West Liberty, Kentucky
Posts: 89
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Fuel pump drive?
Along the same lines, what about the fuel pump pushrod?
If the mechanical fuel pump is not going to be used, can the pushrod for the fuel pump be left in place, or does the accessory case need to come off and the rod removed?
Thanks
__________________
Kevin Holbrook
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