Tach = tachometer. For model airplanes, its an optical device that when held behind the prop, detects the propellor passing in front of it. They can be had for $30-40, can be set for 2, 3, or 4 bladed props, and indicate how fast the engine is turning. I find it an essential element for fine tuning, since it is much more sensitive to small RPM changes than my ear. I use the [link=http://h1069795.hobbyshopnow.com/products/description.asp?prod=HAN156]Hanger9 ([/link]$35 from Hobbytown) but there are less expensive versions.

Brad

Oh yeah, i saw one at the field. It looks pretty cool. I dont have much cash though, so it will have to wait.

Tachometer: a device used to measure the rotational speed of a spinning device [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXPT31&P=RF]http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXPT31&P=RF[/link] For model airplanes, they're usually optical devices that can count the times a propellor blade breaks the light entering a photo sensor.

The most popular brand is Loc-Tite. It's a chemical you place on the screw threads before screwing your parts together, and it makes it difficult to unscrew so that it'll stay tightly put together even when the engines vibrations get to it. There are several different grades, as well. The red type is quite permanent. The blue holds well, but is removable with some effort. For most situations, I use the blue.