Tach on the Cheap . . .

[Steve]

Link for this Tach was posted on the Lonesome Buzzards: http://www.ebay.com/itm/4-Digital-Red-LED-Tachometer-RPM-Speed-Meter-Hall-Proximity-Switch-Sensor-NPN-/291122353744?pt=LH_DefaultDomain_0&hash=item43c83e9650

Photo attached shows it travels by the way of Hong Kong via USPS - took 10 days and postage free...

Needs a box 1.5"x2.75" and 2" deep to cover board and house a 9v disposable battery...

The Hall Sender cable could be longer for our application and it's minimal length calls for mounting the display at the firewall in the cab - display digits are robust and very visible up there - you actually could mount out on the top of the engine somewhere and see it...

The Hall sensor needs a magnet spinning about an 1/8" away at crank speed... My plan is bond the magnet to the end of the longest prop bolt with epoxy and a longitudinal wrap of fiber glass for good measure... A bracket will be fabricated to position the sensor pictured...

I would be remiss if I don't point out that Leonard didn't put a Tach on the LE prototype - he checked the engine with a hand held optical Tach on the ground and flew many hours with no Tach...

[cluttonfred]

The Tiny Tach and similar electronic tachs come in enough variations that one will work with just about any engine.  For the low price and negligible weight, it seems silly to do without.

[Steve]

The Tiny Tach and similar electronic tachs come in enough variations that one will work with just about any engine.  For the low price and negligible weight, it seems silly to do without.

Acquiring a clean impulse signal to the Tiny Tach & other similiar Digital Tach's has been problematic... See postings by Les H, Tom H & Joe S on the challenges... This Tach is my first encounter with one driven by a Hall Sensor AND inexpensive...

[riorex2002]

Will the Hall pick up  sensor function with the magnet imbedded in a rotating metal member or will the magnet have to stand out on its own to give a signal.
Rex

[Steve]

Will the Hall pick up  sensor function with the magnet imbedded in a rotating metal member or will the magnet have to stand out on its own to give a signal.
Rex

Info here that gets into that: http://www.allegromicro.com/en/Design-Center/Technical-Documents/Hall-Effect-Sensor-IC-Publications/Hall-Effect-IC-Application-Guide.aspx#Q27

[Sam Buchanan]

The Tiny Tach and similar electronic tachs come in enough variations that one will work with just about any engine.  For the low price and negligible weight, it seems silly to do without.

Acquiring a clean impulse signal to the Tiny Tach & other similiar Digital Tach's has been problematic... See postings by Les H, Tom H & Joe S on the challenges... This Tach is my first encounter with one driven by a Hall Sensor AND inexpensive...

The commercial version of the Tiny Tach I used for three seasons was quite reliable. It is sensitive to how the pickup wire is attached but once dialed in you can forget about messing with it.

I have to wonder what effect on prop balance a magnet on a prop bolt would have, and how hard it would be to fabricate a sensor mount that could withstand the pounding of the 1/2 VW.

But choices are good and it's valuable to see another option.

[rfeenstra]

I had a very difficult time dialing in the pickup for the TinyTach on my A65.  Never did get it to be consistent.  Have since put one in that works off the P lead.  Works well.

[Steve]

I had a very difficult time dialing in the pickup for the TinyTach on my A65.  Never did get it to be consistent.  Have since put one in that works off the P lead.  Works well.

The P lead driven Tach's are Ok if you have dual ignition - there is a precistent history of this method failing or making a mag erratic... See Teenie2 Yahoo Group... Joe S had an experience with it on this Forum...

[rfeenstra]

So far it has worked flawlessly. I do have dual ignition.