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  Using the Induction Heater – Removing a stuck fan


One of the banes in the lives of HVAC and maintenance mechanics is the removal of corroded, rusted in place fans, pulleys and other objects from the shafts they’re mounted on.  Gear pullers often do irreparable damage and acetylene torches can often overheat and warp.  Induction heat is perfect for this application.

I’m scrapping an old RV air conditioner so my friend Matt and I decided to demonstrate how the Fluxeon® Roy induction heater can be used to ease the job.

fan hub

Fan hub and induction coil

This photo shows just how bad the situation is.  The AC had been on the RV for almost 30 years.  Then it laid behind my cabin for several years exposed to the weather, until I could find someone to help me move it.

Not only is the shaft rusted to the shaft but the set-screw is also rusted up.  I bent an Allen key trying to turn it.

Finally, the work coil. Almost anything will do. In this case I found a hunk of electric motor hookup wire. I put some fiberglass sleeving on it in case the rubber insulation burned off and then hand-formed it to make about 3 loops around the fan hub.

End of the shaft showing rust.

End of the shaft showing rust.

This photo shows the other side of the shaft. Not only is the shaft heavily rusted but the end is mushroomed where someone had previously tried to remove the fan by beating on the shaft with a hammer. Therefore before we started, I took a Dremel tool and ground down the mushrooming on the end of the shaftSetscrew is now finger-loose

After just a couple of minutes of heating, the set screw loosened such that I could turn it with just a couple of fingers.

The heating begins

The heating begins

Let the heating begin! Notice the smoke rising from the hub area. This is oid oil and rubber insulation being vaporized. I heated the hub for about 3 minutes to about 900 deg F. The heat was very smooth and even, with no hot spots. Only the hub was heated. The blades remained cool and un-blackened.

shaft is out

Shaft is out. After the 3 minutes of heating, I laid one fan blade on my bench, held the opposite one and gave the shaft a gentle tap with a brass hammer. It fell right out!

after heating

The Work coil after heating

This is what the work coil looked like after the heating. The rubber smoked a little but was not melted. The sleeving proved to be un-necessary.

the corroded shaft

The corroded shaft

The shaft after the fan is removed. One can see just how badly it is corroded.


fan hub after heating

The fan hub after heating

The fan hub after removal. Notice that it is still tight on the blade spider, is not warped or ben and with the application of a little oil, is ready for immediate re-use.

The dent marks were made by someone else in the past trying to hammer the fan off without the help of Roy

The Bearing

After removing the fan, just for fun we decided to remove the sleeve bearing which was also stuck.

Stuck bearing

The stuck bearing and work coil

This photo shows the work coil I whipped out from some #8 solid copper ground wire and some siliconized fiberglass sleeving.


Work coil in place

Work coil in place

Work coil in place.

turn on the heat

Smoke from oil burning out of bearing

Turn on the heat! The smoke is from the oil burning out of the porous sintered Oilite sleeve bearing.


Hot bearing

Bearing at temperature

The bearing really likes induction heating! At this point, it is loose on the shaft and can be lifted up with a pair of pliers.

ready to be removed

Bearing ready to be removed

The bearing, ready to be lifted off. Notice that the shaft didn’t get very hot at all. Yet another benefit of induction heating.


Induction heating makes the miserable and time consuming job of removing stuck objects from shafts easy and painless. For more info on the Roy© line of induction heaters such as the Roy 2500 used here, go to

Posted by neonjohn on October 1st, 2014 under Electronics, HVAC, Induction heating, Misc |
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  DSO203 Open Source 4 channel digital oscilloscope


Front Veiw of the Scope

Front View of the Scope

Recently my business partner, Garett Churchill surprised me with a little goodie. A 4 channel DSO that will fit in my shirt pocket.

We’ve been very busy lately so I didn’t pay it much attention other than to charge it via the USB port. Today I decided to take a look.

The first thing I noticed on the back was the Creative Commons symbol. That really perked this open source advocate’s ears up! The first thing I did was go to their website (through Google Translate – the site is in Chinese. The whole site is a BBS/forum format which I found quite un-useful.


Scope Schematic

A mini-optical disk came with the scope so I popped it in the drive. There were many jpg photos that Irfanview could not render, though the Linux document viewer could. And a manual. And source code. And a schematic! This this truly is open source! Is that amazing or what?

The first thing to do was to connect it to a signal generator and see what it can do. The photo above shows it displaying a 500kHz square wave. The fluff on the edges of the square waves are caused my my less-than-perfect connection


probe connection

A not-so-50-ohm-connection


Don’t hardly think that’s 50 ohms across there!

Next I connected to my Rigol DSO and compared the amplitude and time interval measurements. Right on the money. For a little scope that cost around $169 (sleazebay), I’m getting more and more impressed.

Another thing that is impressive is how easy it is to upgrade the firmware. No special PC software needed. Just hold a button for a few seconds and it mounts like any other drive. Here are the complete instructions.:

If you want upgrade the firmware of DS203, PLS follow these steps:

1. connect the DSO to PC with a USB cable ,then press
“>II” key when power on.

2. After a few seconds , you can see a “DFU storage”
in your PC , copy your firware file “*.hex” to the
“DFU storage” . Note that only one file can be
copied each time. And waiting for auto-reboot.

3.Restart the DSO.


Simple enough, eh?

I next took the scope out to my truck and repeated some of the tests I outlined here. The results were the same.

Needless to say, I’m pleased! Here are some more photos of the instrument

back side

Back View

left side

Left Side View

right side

Right Side View

I really hate to recommend anything where sleazebay is the only source so I went looking. Good old came through. Go here and type in “DS203″. Several vendors will be reurned. Bear in mind that the posted prices are very soft! Feel free to haggle. Be sure you get the version with the two probes, a carrying case and the mini-CDROM.




Posted by neonjohn on August 11th, 2013 under Electronics, Neon and other lighting, Product Reviews |

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Yep, got hacked about 3 weeks ago.  Very slick hack that didn’t alter the operation of this blog while it tried to inject bad stuff into the reader’s machine.  The very fine folks at my host, found the malicious code during one of their periodic security scans and informed me about it.  They also helped me get rid of the bad stuff.  That basically involved saving off all my content, deleting WordPress, installing a virgin copy and copying back over my content.  A nice afternoon wasted.

I did a dumb thing that allowed the hack.  A couple of years ago I was about to make some major changes to my blog so I copied the existing blog over to  There was a vulnerability – later fixed – in that version of WordPress.  So while my active copy got its automatic updates, that saved copy just laid there waiting for a malicious robot to find it.

Lesson learned from this: Never leave any detritus laying around on a computer exposed to the web.

This is the first time I’ve ever experienced any form of maliciousness.  I run Linux here at home so I’m pretty well shielded from the cruft that attaches to Windows.  I agree with others who have said that it makes one feel violated.  Just 5 minutes alone with the perp…







Posted by neonjohn on August 4th, 2013 under Computing, Hints and Tips, Internet |
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  Cutting My Way To Paradise


Inverter Ready to go

Inverter Ready to Go

When I say “cut my way to Paradise (here in Green Cove) I mean it literally.  On my to the metropolis of Tellico Plains, I navigate about 25 miles of winding country road that follows the Tellico River.  On any given day there can be one or more trees down across the road.  That’s a sure bet after the monsoon we’ve had this summer.

What this means is that you either carry a chain saw or you sit and wait on someone who does have a chain saw.  In the winter, that wait can be a long time!

Ever since I’ve lived up here I’ve carried a small gas powered chain saw in my vehicle.  Several problems with that.  First off, it stinks up the vehicle with the smell of gasoline.  Two, fresh gasoline must be kept in the thing.  Three, in cold weather it’s hard to start.

Being an electronics nerd, I knew there had to be a better way.  The Better Way is an electric chain saw powered by a 2000 watt inverter and 100 ft of light gauge cord.  Since I didn’t want to drill holes in my new truck body and didn’t really want the inverter exposed to the elements, I used a pair of Anderson connectors to make the inverter to battery a quick connection.  The details of how to do this are described here.

And as long as the battery was equipped with an Anderson connector, I decided to make a heavy duty set of theft-resistant jumper cables.  Somewhat theft-resistant because they’re useless to anyone without an identical setup to mine.  The details of that project are here.

I’ve had this installed about 2 weeks and already I’ve had to use it once.  Returning to my cabin late night I found a small tree across the road.  Only about 3″ in diameter, I could have probably put the truck in 4WD and creeped over it.  But this was a perfect opportunity to try out the new toy :-)  10 minutes later, the tree was cut up and off the road and I could continue home.  Success!


Posted by neonjohn on July 26th, 2013 under Cool Stuff, Projects, RV/Camping |