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Mission Statement 

The purpose of FLAPS-2-APPROACH is two-fold:  To document the construction of a Boeing 737 flight simulator, and to act as a platform to share aviation-related articles pertaining to the Boeing 737; thereby, providing a source of inspiration and reference to like-minded individuals.

I am not a professional journalist.  Writing for a cross section of readers from differing cultures and languages with varying degrees of technical ability, can at times be challenging. I hope there are not too many spelling and grammatical mistakes.

 

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I use the words 'modules & panels' and 'CDU & FMC' interchangeably.  The definition of the acronym 'OEM' is Original Equipment Manufacturer (aka real aicraft part).

 

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Journal Archive (Newest First)
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Thursday
May262016

Trim Wheel Nut Tool - New Design

A potential problem when using an OEM Boeing throttle unit, is removing the nut that secures the trim wheels to the side of the throttle.  The nut has been designed in such a way that loosening it can only be done with a specialised tool.  Attempting to use a screwdriver or pliers may burr the nut, or slip causing damage to the trim wheel.

LEFT:  The redesigned Trim Wheel Nut Tool (click to enlarge).

In an earlier post I examined how a simple tool had been designed to easily remove the nut from the spline shaft that holds the trim wheels in place.   Although this tool was functional there was room for improvement in its design and manufacture.

New Design and Improved Engineering

The tool, has been redesigned and incorporates an aluminium cylinder that has been produced from a solid block of aluminium using a milling machine.  The inside of the cylinder has been milled and a set screw securely inserted.  

The outer flange, adjacent to the set screw has then been machined so that two ridges, approximately 1mm in height are either side of the set screw.  The set screw mates with the female located on the end of the spline shaft while the ridge provides extra purchase by mating with the indents in the nut.  In addition, a circular hole 8mm in diameter has been drilled through the cylinder enabling a similar sized piece of metal, or the shaft of a screwdriver to be inserted.  This allows additional purchase and leverage should the nuts be difficult to loosen.   Finally, the aluminium on the outside of cylinder has been slightly scoured to facilitate better grip.

Round and Round

The trim wheels are continually rotating back and forth as the aircraft is trimmed.  This rotation causes the nut, that secures the trim wheels to the spline shaft to, over time, become tighter and therefore more difficult to loosen.  This firmness is often exacerbated if working on a throttle unit removed from a real aircraft, that has not had the spline nuts removed for several years; corrosion and caked grease can easily cement the nuts in place.

LEFT:  New design has easier mating which enables greater purchasing power for removing tight spline nuts (click to enlarge).

This tool, although not an OEM part, is more than adequate to loosen the most determined nut.

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Reader Comments (4)

I want one..........

May 26, 2016 | Unregistered CommenterHarold Stoldt

Funny thing - after I reassembled my TQ I did not install this shaft and nuts back. It works fine without them over 2 years. :)

May 26, 2016 | Unregistered CommenterElephantAir737

You are fortunate that the main cogs (that the trim wheels attached over) did not come away from the throttle housing. If this occurs the cogs and bearings that are held together by the main cogs will fall into the central unit. Putting the bearings back together is a very tricky, if not an impossible process. The long metal shaft and nut hold the trim wheels and main cogs together.

I guess if your trim wheels are only moving slowly then there isn't a problem, however I have 4 speed trim which changes the rotation speed depending upon the aircraft configuration. Sometimes the trim wheels rotate quite fast!

Cheers, WilloW

May 26, 2016 | Registered CommenterFLAPS 2 APPROACH

Thanks Iain, I will install it back, but first I will make the same tool! ;)

May 26, 2016 | Unregistered CommenterElephantAir737
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