50-93 Sketchy metallic adjuster

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wilder11354
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Hand Fed Coal Boiler: Harman SF260 Boiler
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Other Heating: crown oil boiler, backup.if needed
Location: Montrose, Pa.

Post Mon. Oct. 30, 2017 8:25 pm

yesterday i layed behind stove....warm it was, and looked up from bottom, as to how draft door spring works. not absolutely sure, ..bimetallic springs a C/(s-tine shape) like a cultivator spring, adjuster knob for adjusting it turns a thick steel plate, that has a spiral cut groove it in , like a pinwheel?!. Way excessive movement of plate until tensions transmitted to bi-metallic spring. cut slotin wheels shot? bolt/pins worn?! not sure. So i been adjusting best i can with balls on chain. REALLY do think its time for new adjuster assy for fire control draft door.
IMG_20171030_180000[1].jpg
Got it adjusted to burn at about 300* on coal box side, using rutland thermometer, Winds have been great since last night, got MPD choked down to about half..... lower draft door adjuster about...1/2 moon size gaps. 200* on firbox doesn't keep up with nightly outside temp drops, like it to always be 70>75* in section of house.

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freetown fred
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Post Mon. Oct. 30, 2017 9:25 pm

Very rarely do bimetallic springs go. As anything with coal, it would take 1 + hrs. for that to show any change/movement. When the stove was cold did you shut the flap all the way & set ball chain so ya got approx. 1/8 reveal? Are you cracking ash door vents? I'd lighten up on those ash vents. I never use mine unless we get into sub-zero temps.

DENNIS BAUER
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Post Tue. Oct. 31, 2017 3:20 pm

Freetown, can you explain setting the 1/8 reveal a little bit more? new to the stove and I'm not sure I'm understanding that part?

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freetown fred
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Post Tue. Oct. 31, 2017 4:39 pm

It was shared with me if --when the stove is cold-- if I left the 1/8 inch reveal (flap open1/8) when I started burning she would close all the way & it did work out that way with my 50-93. I bought mine used & the chain was unhooked so it just gave me a starting point & worked out well. I hope that clears my post up a little for ya D. If not get back with me.

DENNIS BAUER
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Hot Air Coal Stoker Stove: Keystoker 105 - SOLD
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Post Tue. Oct. 31, 2017 5:11 pm

THANK YOU!

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wilder11354
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Location: Montrose, Pa.

Post Tue. Oct. 31, 2017 7:37 pm

with the cold stove, adjusted to 25 balls, but ZERO setting pulls open up on chain, 1 setting or so its no up or down change. so i adjusted some for that....Yet turning adjuster higher for more draft knob turns .... MANY numbers before (bimetallic)retensions chain with heat. Knob scale starts at 0 goes to 14 i believe. right now avg settings in 6>8 range.area. lower draft vents are about sliver moon or so. This stoves about 15 years old..... no idea of past history other than... serious over heat situations to warp grates and burn away grate cradle.

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freetown fred
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Post Tue. Oct. 31, 2017 7:49 pm

Now ya just gotta tinker Bill. Be patient with the old girl!

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windyhill4.2
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Post Tue. Oct. 31, 2017 8:11 pm

wilder11354 wrote:
Mon. Oct. 30, 2017 8:25 pm
..bimetallic springs a C/(s-tine shape) like a cultivator spring
I always thought those bi-metallic springs were flat steel wound into a circle..
I tried to find a picture of the Hitzer spring ,but no luck.

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Rob R.
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Post Wed. Nov. 01, 2017 6:00 am

David, I thought for sure I had a picture of the inside of that control, but I do not. My memory is the same as yours, flat steel wound in a coil, like an automatic choke on a car.

The control itself is not expensive, so if it appears to be messed up it is not the end of the world. When working correctly, it keeps the temperature of the stove very stable. Some people have even adapted the control to other makes of stoves.

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freetown fred
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Post Wed. Nov. 01, 2017 7:03 am

Been yrs but I'm thinkin--flat spring wound up--YES just like a choke spring--pix always help!!

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lsayre
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Post Wed. Nov. 01, 2017 9:13 am

It's actually a strip of two different metals bonded (glued) together, and although they are generally wound into a spiral they don't have to be. Since the two different metals have differing expansion and contraction rates due to applied heat or cooling, the strip bends whenever the temperature it is exposed to is different from the temperature when the metals were first glued together. Generally the ones made for stove application are configured to relax and thereby lengthen upon temperature rise, and contract and thereby shrink in length (coil up more) upon temperature drop.

My first guess is that in order for them to naturally wind up into a spiral in the first place they are initially bonded together as a flat strip at very high temperature. Cooling then naturally causes the strip to coil up.

Dial thermometers work the same way. As the coil relaxes a bit with the heat of the day it moves the attached dial pointer toward higher temperatures upon the scale, and as it cools at night it winds up a bit and moves the attached pointer toward lower temperatures upon the scale. Since the contraction/relaxation with temperature change is highly linear, the dial thermometers temperature scale is linear.

I assume that at least some aquastats and T-Stats work the same way. They contract or expand a strip of bonded dissimilar metals to somehow make or break an electrical circuit. In the older T-Stats there was a tube attached to the bimetallic coil with a bead of mercury in it, and as the tube was tilted by temperature change, it either made or broke the circuit due to the mercury moving in the tube. Perhaps most aquastats however use "thermal expansion/contraction wax" instead of a bimetallic strip.

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windyhill4.2
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Post Wed. Nov. 01, 2017 9:20 am

My suspicion on the s shape is that someone turned the knob the wrong way when the stove was running hot & bent the end of the spring the wrong way,making it look like an s.

BUT, i could be wrong,they may have made it in an s shape.I am having a hard time picturing how an s shaped spring would work tho.

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freetown fred
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Post Wed. Nov. 01, 2017 11:48 am

I'm gonna pull mine apart & get to the bottom of this----NEXT SPRING!!!!!!!!!!! LOL WH's explanation seems to ring true.

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wilder11354
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Hand Fed Coal Boiler: Harman SF260 Boiler
Hand Fed Coal Stove: Hitzer 50-93
Coal Size/Type: nut or pea, anthracite
Other Heating: crown oil boiler, backup.if needed
Location: Montrose, Pa.

Post Wed. Nov. 01, 2017 7:29 pm

s-tine/c- tine.... point is... either both ends of spring caputered, or one end uncaptured...rests with tension by design. Excessive dial play is what i question..WHY 6 numbers by scale cold or heating to make it adjust??

Den034071
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Post Wed. Nov. 01, 2017 9:16 pm

Wider call Hitzer .Last year I replaced the Whole Bi Metal thing .I think it was around 25 bucks an gave me peace of mind .I damaged mine while moving it to my shed for painting .Call Dean at Hitzer . jack

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