Mounting Air-Core Inductors

D

DWCriss

New Member
I've had a few inductors that have come loose from the hot glue or other glue mounting to a crossover board.

I'm wondering if securing an air-core inductor with a bolt and washer would have any effect on the inductance of such a conductor. If so, would a different metal bolt have any lesser effect? (stainless steel, brass, etc.)

Thank you....

Dave
 
Register to hide this ad
Yes, putting anything metal around the inductor could affect the coil. If you put one through the center you will most likely alter the mH value of the coil.

They do make nylon bolts that will not alter the mH value and there are other methods to mount it as well.
 
Last edited:
Thank you for your replies.

I didn't think of nylon bolts - I'll give that a try. Zip ties would be easy but would make it harder to mount the cross-over board flush with the back panel.

Dave
 
I have used liquid nails to glue 18 gauge air core inductors in place.

For some very large 12mh 14 gauge air core inductors I use brass screws to secure a piece of wood over the inductors.
The brass screws are used a couple inches from the the outside of the inductors to hold the wood over the inductors in place.
 
Thanks Jim and Don.

I may have to look closer at zip ties or glue. Nylon bolts are hard to come by in the lengths I'd need.

Using liquid nails, I'd need to have some of the glue spread back over the plastic hub the coil is wound on. I have two boards on which 4 inductors have come loose from the hot glue or whatever glue was used.
 
You can use stainless steel screws to hold the air core inductors down. They are easier to find than brass. Just check the screws with a magnet. If the magnet will not pick them up, they are good to use.
 
You could also use "real" brass machine screws. Brass is non-metallic. Just cut a scrap 1/4" ply to hold down the top of the inductor. Drill a hole, and thread thru to the base.

Kinda pricy, but you're only using a couple. Any hardware store should carry them.

Good Luck.
 
I used aluminum screws through plastic washers for my last pair. Troels Gravesen uses wood dowels in the middle and glue underneath.
 
cablephil212 said:
You could also use "real" brass machine screws. Brass is non-metallic.
Click to expand...

Umm, not to be picky or anything, but don't you mean non-magnetic?

If you do use stainless steel screws be sure to use ones that are not hardened. SS generally has very low magnetic properties but as it is hardened it gets more and more magnetic. If you are going to use metal screws brass or alluminum would be best.

I like the wood dowel suggestion, so much so that I think that I will borrow it. :thmbsp:

Cheers,
James
 
Bratwurst7s said:
I like the wood dowel suggestion, so much so that I think that I will borrow it. :thmbsp:
Click to expand...

Cool! Details here:

http://www.troelsgravesen.dk/tips.htm

attachment.php
 

Attachments

  • image.jpg
    image.jpg
    18.8 KB · Views: 59
Metal, brass, aluminum or anything else through the center is bad. Inductance will change and distortion will go up, sometimes a lot. Metal screws on the outside don't bother much. Cut a strip of masonite to go across the coil and use some long wood screws on either end to hold it down. Me, I just use hot glue.

OT- There used to be a thing called a "tuning wand" used by radio service people. It was a wood or plastic rod with a ferrous slug on one end (iron or ferrite), and a copper, brass or aluminum slug on the other end. To find out which was a coil had to be adjusted, you'd stick the thing in the coil. The ferrous end would raise the inductance, the brass end would lower it. http://antiqueradios.com/forums/viewtopic.php?f=6&t=160010 Never had a need for one, but always thought the idea was way cool.
 
ConradH said:
Metal, brass, aluminum or anything else through the center is bad. Inductance will change and distortion will go up, sometimes a lot. Metal screws on the outside don't bother much.
Click to expand...

That reminds me. I bought a pair of Grundig HiFi Box 650b's for a friend at the end of the year and when checking the crossovers for cap values I noticed what looked like steel screws through the middle of 2 of the 3 coils as fasteners. Got to remember to remove them when we recap them later this month. Thanks for the reminder.

Cheers,
James
 
Bratwurst7s said:
Umm, not to be picky or anything, but don't you mean non-magnetic?

If you do use stainless steel screws be sure to use ones that are not hardened. SS generally has very low magnetic properties but as it is hardened it gets more and more magnetic. If you are going to use metal screws brass or alluminum would be best.

I like the wood dowel suggestion, so much so that I think that I will borrow it. :thmbsp:

Cheers,
James
Click to expand...

OK. You Got Me there. :D

Yes, non magnetic.
 
Bratwurst7s said:
I bought a pair of Grundig HiFi Box 650b's for a friend at the end of the year and when checking the crossovers for cap values I noticed what looked like steel screws through the middle of 2 of the 3 coils as fasteners. Got to remember to remove them when we recap them later this month.
Click to expand...

Although maybe they were voiced that way?
 
You must log in or register to reply here.
Back
Top Bottom