[coastrc]

I think I have a pretty good feel for tightening bolts, but was thinking of getting one because I like things to be "done right" Probably more important to have if I rebuild one of my engines, so there would be other uses.

My research has lead me to believe that decent one is going to cost me $150. otherwise doing it by "feel" is probably as good or better than buying a cheap one.

I also read that some guys replace prop bolts after every 3 times of torquing them...that seems extreme! Anyone else do that? or how often do you replace bolts?

[itizme]

Most good techs know the right feel and have proven time and time again that they are correct BUT you will always know you are in the correct range when metered.

Prop bolts, don't know why anyone would change that often, I suspect that a loose bolt incident sheared someone's bolts so it is likely an effort to be safe. It has been suggested that a Cf backplate not be used but I don't know if anything has been proven on that one.

[coastrc]

The reasoning for changing bolts was because they "stretch" each time they are torqued.

I'm not buying that they need to be changed after being torqued 3 times, otherwise I better order a box of bolts lol.

[Lazy Ace]

Where does one find the torque specs for the engine bolts and prop bolts. I would think there are different ones for each prop depending on manufacturer and composition of the prop itself.

Dennis

[JoeT]

Originally Posted by Lazy Ace

Where does one find the torque specs for the engine bolts and prop bolts. I would think there are different ones for each prop depending on manufacturer and composition of the prop itself.

Dennis

Bolts are torqued according to the material (Grade) and diameter of the bolt. It's an SAE thing, you do not torque according to the prop.

http://www.portlandbolt.com/technica...-torque-chart/

https://www.engineersedge.com/calcul...orque_calc.htm

http://www.futek.com/boltcalc.aspx

[coastrc]

DA has specs for there engines somewhere but i read a report of a wood hub being compressed by using their recommended torque.

Sounds like 45 in/lbs for wood & 65 in/lbs for CF is good for M5 bolts. For the bigger engines with M6 bolts I read 75-90 in/lbs.

[coastrc]

Do you use one Joe?

[Flypaper]

All wood props will compress with the constant pressure on them. They need to be retightened every so often. I'll wager if you torque the bolt to 45 ft. lbs., 6 months down the road you'd be lucky to have 30 ft. lbs. on it. That's enough to fling the prop off. Had it happen!!

[hsh]

Originally Posted by Flypaper

All wood props will compress with the constant pressure on them. They need to be retightened every so often. I'll wager if you torque the bolt to 45 ft. lbs., 6 months down the road you'd be lucky to have 30 ft. lbs. on it. That's enough to fling the prop off. Had it happen!!

The torque quotes are for inch/pounds. DA manual for my DA100L says
75 in lbs for wood props
90 in lbs for carbon fibre
also 90 in lbs for spark plugs

[JoeT]

Originally Posted by coastrc

Do you use one Joe?

Yup I do when I'm at home. At the field, I don't. I do check it on a regular basis, as wood props tend to "crush" at the hub which requires re-tourquing.

I now use only CF props on the big planes, so no issues with them, they torque up just fine and stay that way.