Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

First off, making your own heater blanket isn't for the faint of heart or anyone scared of electricity.  I have been around electricity all my life and at one time I thought I'd be in some kind of an electronics repair guy.  Some how I ended up going into Broadcast TV Engineering and while I did do a lot of component, microwave, UHF transmitter repair in my 1st 5 years and been in software for the 25+ years. 

Basically, treat electricity like a whore - you can ha a lot of fun but if you get a STD you are screwed and might die a horrible death!  AKA - Don't blow yourselves up!

Items used:

• McMaster-Carr (85825K42) Flexible Electrical-Insulating Mica, 23" x 39", 0.008" Thick
• McMaster-Carr (69405K54) Noninsulated High-Temperature Ring Terminals, 900°F Maximum Temperature, for 16-14 Gauge and Number 10 Screw
• McMaster-Carr (2573K41)  Electrical-Insulating Tube Sleeving, Expandable, 0.080" ID (7,000V -65° to 390° F)
• Jacobs Online (RW132035100) Nichrome Ribbon Wire, 1/32 X .0035 X 100ft
• Latex Gloves - the kind you get 50 in a box from drug store.

The #90 heater is split into parts and straddles the one mounting screw.  It goes Tank, Heater Blanket, Iron Mount Plate.  Then one nut to squish Iron Mount Plate to the tank (with the heater blanket in between).

There was one side of the heater that didn't blow - it measured 16.7 ohms (no power tab and disconnected from the other side).  The first time I put it together I didn't make the Electrical-Insulating Mica wide enough, as I could see it glow.  While it looked really cool to see, I turned it off to create new Electrical-Insulating Mica sheets!

Each of the strips I made, I used some mica from the original strip that did blow - I divided them up and balanced them on my hand made ones.  So two larger sheets on top and bottom.  Then two strips I made, with original mica for each side.  I then wrapped Nichrome Ribbon Wire, 26 times, around these strips.  Each measured 16.4 ohms (no power tabs / not connected.  I'd say that is pretty close!

Next I used about 1/4 of a McMaster-Carr Ring Terminal, where I drilled two tiny holes to pull the Nichrome Ribbon Wire from the two strips. Original bridge was unusable. Next I was able to use the original power tabs to attach to each of the newly made strips.  Once together and tied to the heater box power leads, my DMV read 33.7 ohms.

Photos attached are:

• Mock up - making up the basic setup of mica strips.  Note: I did end making the larger ones wider and a just a tad longer.
• Comparing old and new Nichrome Ribbon Wire - they are darn near equal.
• Heat Pattern - when I saw I needed wider mica, this let me see the heat patter.  The mica gets really hot and when I first turn her on I did get some smoke but it dissipated pretty quickly.