Hand Held Tach

The radio modelers have developed a useful market for gadgets.
I bought a tach a while ago, and I keep meaning to mention it
here.

The price was right - around $25.
It's intended for measuring off two or three blade props.
In other words, it counts either two flashes or three as a revolution.

When I point it at this screen (Free Agent News Reader) it registers
1800 rpm i.e 60 flashes / sec if I select two blade, or
1200 rpm if I select 3 blade. If I point it at a compact fluorescent,
it indicates 3600 rpm (120 flashes/sec)

People apparently use it with reflective patches stuck on their props
Half inch numerals on an LCD display with a prop image (2 or 3 blade).
Battery lasts a long long time.

"Tower Hobbies Digital Mini-Tach"

Brian W

Brian Whatcott wrote in
:

The radio modelers have developed a useful market for gadgets.
I bought a tach a while ago, and I keep meaning to mention it
here.

The price was right - around $25.
It's intended for measuring off two or three blade props.
In other words, it counts either two flashes or three as a revolution.

People apparently use it with reflective patches stuck on their props
Half inch numerals on an LCD display with a prop image (2 or 3 blade).
Battery lasts a long long time.

"Tower Hobbies Digital Mini-Tach"

I modified one of those some years back... worked quite well. Never needed
any reflective patches for the prop of a real aircraft... works just fine
in daylight.

The two mods I made we

1. Changed the internal clock frequency so that it read out in tens of
RPM. The stock model I bought (only one they had back then) read out in
hundreds of RPMs. [Lots of model aircraft have props that turn in the tens
of thousands of RPM.]

2. Made the sensor a plug-in. This gave me the option of using it as
originally designed (fine for a SEL single), or on a cable from within the
cockpit (for a twin, with the sensor taped to the wing).

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1300 Koenig Lane West fax 512-371-5716
Suite 200
Austin, Tx 78756
-----------------------------------------------

Brian Whatcott wrote:


When I point it at this screen (Free Agent News Reader) it registers
1800 rpm i.e 60 flashes / sec if I select two blade, or
1200 rpm if I select 3 blade. If I point it at a compact fluorescent,
it indicates 3600 rpm (120 flashes/sec)


What rpm should I expect if I'm using MS Outlook as a newsreader?:-))

Seriously, I've seen several folks using the hobby store tachs at the
airport. As far as I know, they don't require any patches to be stuck to the
prop. The big upside is that they cost about 10% of what specialized
aircraft optical tachs (Prop Tach, TruTach) cost. As with most things, if
it's for an airplane, multiply the normal price by about 10.

John Galban=====N4BQ (PA28-180)

--
Message posted via http://www.aviationkb.com

On Wed, 20 Aug 2008 22:01:34 GMT, "James M. Knox"
wrote:

Brian Whatcott wrote in
:

The radio modelers have developed a useful market for gadgets.
I bought a tach a while ago, and I keep meaning to mention it
here.

The price was right - around $25.
It's intended for measuring off two or three blade props.
In other words, it counts either two flashes or three as a revolution.

People apparently use it with reflective patches stuck on their props
Half inch numerals on an LCD display with a prop image (2 or 3 blade).
Battery lasts a long long time.

"Tower Hobbies Digital Mini-Tach"

I modified one of those some years back... worked quite well. Never needed
any reflective patches for the prop of a real aircraft... works just fine
in daylight.

The two mods I made we

1. Changed the internal clock frequency so that it read out in tens of
RPM. The stock model I bought (only one they had back then) read out in
hundreds of RPMs. [Lots of model aircraft have props that turn in the tens
of thousands of RPM.]

2. Made the sensor a plug-in. This gave me the option of using it as
originally designed (fine for a SEL single), or on a cable from within the
cockpit (for a twin, with the sensor taped to the wing).

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1300 Koenig Lane West fax 512-371-5716
Suite 200
Austin, Tx 78756
-----------------------------------------------

I can see the virtue of that remote sensor mod. That would make it a
panel mountable.ay 2.5 X3.5 X 3/4 inch (about)
THe display goes to five digits now, so #1 mod would not be a concern

Brian W