Shinn Brake Spring Tool

Seems like nobody likes to install new springs on the Shinn brakes.  It can be done (sometimes) with a screwdriver using the pry and pop method.  But after one frustrating day spent struggling with my springs (4 of them, 2 on each side), I decided to take the time to may a spring stretcher tool.

I used a gas welder, a hack saw and a die grinder to make the tool.  It's constructed of scrap steel tube.  Photo 1. 

The stationary part of the tool is 2inches of 1/2" tube with a 1/4-20 nut welded to one end.  Also on the nut end of the tube a 3/4 inch by 1/2 inch piece of steel flat is welded on with a slot hack sawed in it to fit the loop end of the spring (the "fork").  (Photo 2)  A 1/4-20 bolt is screwed into the nut on the end of the stationary tube and provides the force to stretch the spring.

The movable part of the tool is a 2 inch length of 3/8" tube that fits nicely inside the 1/2" stationary tube.  One end of the tube is welded closed so the bolt can push it.  And the other end has a 1/2 by 3/8 flat welded on with a "spur" that can grip the hook end of the spring.  (Photo 3)  The movable part also has a 1/8" peg that rides inside a 1/8" slot in the stationary part.  The slot/peg is to keep the movable part of the tool from rotating when the tool is under tension.  (See "IF I make another"  below)

The spring tool is easy to use.  Install the spring loop end onto the brake, Push the fork end of the tool down over the loop to lock the tool in place, Engage the spur in the hook end of the spring and, Crank the bolt actuator until the tool expands the spring as much as you need.   Great for an old geezer like me because everthing happens in slow motion and I can even expand a spring and pause, go get a coffee or something, then come back later and finish the job.  Wonderful!

IF I make another tool.   If I made another tool I would eliminate the peg/slot setup and just have the 1/2 by 3/4 flat ride in the slot.  In other words, make the stationary tube a little longer with a longer slot and no peg.  I'd also put a big handle on the bolt, that little wing nut thing really hurts the fingers!

 

 

Ethanol Fuel Test

If you run auto fuel in your aircraft engine it's best to avoid the kind of auto fuel that contains ethanol.  Sometimes you cannot be sure if the fuel you're using has ethanol or not.  This test is an admittedly unscientific version of the ethanol test on the EAA website.

I use a pint size Mason jar for the test with about a inch of water.  Photo 1 shows the jar with water and a black strip of tape marking the water level.  I colored the water with a little grape juice for the photographs.

Next add 2 or 3 inches of the fuel to the jar.  Put the lid on the jar and shake it for a minute or so to mix the water and the fuel.  Photo 2.  The water will dissolve any ethanol in the fuel sample.

Finally, let the jar sit for several minutes.  The water/ethanol will settle to the bottom of the jar and the gas will rise to the top.  Note in Photo 3 that the "water" level is now nearly to the top of the tape.  The increased volume of water is due to the dissolved ethanol.  If there is no ethanol in the fuel sample, the water level will not rise.

Most folks only care if ethanol is present or not, but (Photo 4) you can calculate the approximate percent of ethanol in the fuel as follows: (1) measure from the tape mark to the new water level, in this example the water level went up 7/16 inch (.437") and (2) measure from the tape mark to the top of the gas, in our example it's about 2 1/4 inch (2.250")  then (3) divide the ethanol amount (.437) by the total fuel added (2.250) and we get  0.19 or 19% ethanol.

How accurate is this test?  Well, the pump where I got my fuel sample was labeled 15%  ethanol (and I measured 19%).  I've also tested several samples labeled "pure gas, no ethanol" and only one of them showed a slight indication of ethanol (the water level on that one sample rose about 1/8 inch, suggesting about 5% ethanol).  So I'm thinking this test is plus or minus 5% accurate...or maybe the fuel compounders have a 5% tolerance!