Miniplane Paramotor Torque Tip
Propeller Torque Values
I try and use 80 inch pounds on wood propellers. On some wood propellers the wood is too soft so I try and go as high as I can, sometimes it can be as low as 70 inch pounds on some wood (Maybe even lower). On carbon props I go with 85 inch pounds.
More Torque Tips
My torque wrench is delineated in inch pounds. If you have a torque wrench that uses Foot pounds you will have to convert to Inch pounds first. Torque is a complicated subject especially if you’ve never had any experience with it. I should have added that it also matters which bolt you have (size and material). 1st. you determine what “material” your bolts are, (ie. heat treated steel, stainless steel, etc). This is usually marked on the top of the bolt. If you change the bolts it matters! I upgraded to stainless steel bolts which have better corrosion resistance near water but are not as strong.
They are marked A2 – 70. Next you verify the size of the bolts. Mine are the standard Miniplane M6. But I have used in the past the Miniplane bolt kit offered as a “fix” for larger props that were breaking bolts. If the paramotor was bought second hand you should check this… not all larger props use this larger bolt but if they do, the torque values would be higher. Once you are sure of the size and material of your bolts you can look up the torque values.
When I Googled torque values for bolts made from A2 70 stainless, in M6 size, it was 77.0 in. lbs. dry, or 69.3 in. lbs. lubricated. Lubrication is yet another variable that can make a difference. I don’t lubricate my bolts because I’m afraid they might loosen up in a high vibration environment holding on a prop. Torque values are theoretical science. There is some wiggle room. In the field is what really matters.
If your bolts are getting loose you are probably torquing them incorrectly or unevenly. If they are breaking you are probably over torquing them. I rounded 77 up to 80 and have never had a broken a bolt or had them come loose. Also, when you first put on a prop on and torque it, you should check after 1 hour to make sure it is still tight at the specified torque. After that it should be fine. If you remove it, you need to it check again after 1 hour. Hope this helps, feel free to use any of this info.
Bolts and knots Metric metric wrench (mm) Torque (N.m) Torque (lbf.in)
Cylinder-head studs M6 10 9 80
Prop M6 10 9 / 11 80 – 100
Engine mountings M6 Allen 4 10 90
… M8 Allen 6 15 140
5 mm diaphragm M5 Allen 4 or hex 8 4
carburetor and plastic flange
crankshaft nuts M 10 x 1,25 hexagon wrench 17 -35 330
(clutch and ignition flywheel)
Spark plug please refer to manufacturer manual (remind the 2 mm washer, use 2,5 or 3 mm washer with very poor octane number )
Muffler flange M6 hexagon wrench 10 hand fasten and stops 1-2 mm before the compression of the spring (5) about 1,5 turn.
For each bolt/nut you can use 1 or 2 drops of blue loctite.