Wing bolts

[868RM]

Does anyone know if liquid nitrogen is too cold for shrinking the wing bolts. I am concerned about messing up the heat treat properties. Thanks Ron

[FLTENG]

I found that dry ice worked very well.

[ChiefPilot]

Originally Posted by 868RM

Does anyone know if liquid nitrogen is too cold for shrinking the wing bolts. I am concerned about messing up the heat treat properties. Thanks Ron

I really don't think you need it, and I'm not sure it would really help all that much anyway given the relatively minuscule reduction in diameter it would offer. A brass set for your rivet gun (low-to-moderate air pressure) combined with some light grease is all you really need to tap the interference fit bolts home.

[Bavafa]

I used dry ice in alcohol and it helped tremendously. The bolt went in with a lite tab on them and shortly later it started tightening up just in time to get the nut on it.

[868RM]

Thanks I will try to find some dry ice. There is plenty of liquid nitrogen around but not much dry ice. I will look some more.

[LAMPSguy]

Try at your largest local grocery store. Dry ice is often available in the front near the checkout counters.

[RV6AussieNick]

If you have liquid nitrogen handy i'd use that, it's a lot colder, just don't burn yourself.

Like the other guy said you probably wont need it, either grease or sealant (pro seal) will work well when tapping the bolts in.

One negative with cooling parts is, as they normalise in temp they attract condensation, that can lead to corrosion later on, that is why sealant is a good idea.

Use a wood or brass drift so you don't mar the cad plating finish.

Good luck with what ever you decide..

[krw5927]

Can't mess up heat treat properties by getting too cold. Once the bolt gets back to room temp the properties are exactly the same as before.

There's probably a point where the bolt would become more brittle and whacking on it with a hammer may not be wise, but I doubt that would be at liquid N2 temps.

[longranger]

Originally Posted by krw5927

...There's probably a point where the bolt would become more brittle and whacking on it with a hammer may not be wise, but I doubt that would be at liquid N2 temps.

I'm a bit skeptical about the last (blue) part of this statement. I'm only a lowly intrumentation engineer, and I know nothing of the metallurgy of Van's wing bolts (other than assuming they are some alloy of high-strength carbon steel) but in several decades of working around liquid rocket test stands I've never seen anything intended to be exposed to cryogenic temperatures (-150F or below) made of carbon steel, due to the loss of ductility at those temperatures. Even with stainless, only certain alloys are used. I know there have been cases of car/truck frames failing in the range of -50 to -100F.

Probably a moot point though, as the bolt at -320F (boiling point of nitrogen) the bolt probably wouldn't require a hammer...

[DanBaier]

Just a little Boelube on bolts that had been kept in the freezer worked for me.

Dan