Chubby Warped Grate

Modern and vintage hand fired coal stove are similar to a wood stove and in some cases can burn either. They need to be regulated and fed by hand usually every 12 to 24 hours depending on your usage. They require no power to operate making them ideal for rural settings with long power outages.
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tcalo
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Post Tue. Feb. 12, 2013 4:36 pm

Wondering if other Chubby owners have run into this problem. I have a refurbished Chubby that I've been using since October. About a month ago I started to notice a piercing noise every time I shook the stove down. The grate didn't seem to shake quite as easily as it did when I first bought the stove. The grate used to glide as if it was on ball bearings, but recently it's been a little stiff to shake. After some research I found the sides of the grate rubbing on the pot support tabs. I didn't think anything of it, just figured the noise was from the grate rubbing on the pot and the stiffer shaking was from ash buildup. I decided to shut down the stove for a cleaning and inspect everything. I found the grate was warped! Hard to believe since I only put this stove into use in October 2012. In fact I'm sure the temps that I've run the stove at have been well below 500. I normally run the stove about 350 - 450. About a month ago the temps have dipped extremely low and I ran the stove about 550 - 575, occasionally hitting 600 - 625. I did run into the grate problem before the temp change. The only other time the stove may have seen a hot fire is during start up when I had a wood fire burning, but that was only a few times this season and only lasted for about an hour or two. I got a new grate from Larry and it's been in the stove for about 2 weeks now. So far so good, only time will tell! Could I have possibly had a bad grate? Any advice would be great.
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franco b
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Post Tue. Feb. 12, 2013 5:33 pm

Ash build up in the ash pan can overheat the grate.

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ONEDOLLAR
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Post Tue. Feb. 12, 2013 5:52 pm

tcalo

You very well could have a bad grate. It can happen. Anything that is manufactured can have defects.

The grate in my Jr is over 30 years old and it has taken a heck of beating over the years from its previous owners and myself as well when I first started burning coal. I didn't know it when I bought my Jr but someone had welded the grate on my Jr. Still works!

I will bet what happend is just a fluke. Please keep us posted.
It is the small things in life that push us over the edge........

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dcrane
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Post Tue. Feb. 12, 2013 6:03 pm

with cast iron in particular quality can vary greatly (several different foundry's were used over the years im sure), VC is about the only stove Co. that actually has their own foundry. having said that... the grate warping is one of the very few problems that do occur with the chubby (hinge pins and door hinge casting being the other one), my guess is most grates in the chubby last at least 10 years either way and its hard to complain about that. Its fantastic that Larry is still around and saved all his molds for these parts to be available for a reasonable price to anyone who needs them!

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tcalo
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Post Tue. Feb. 12, 2013 7:54 pm

Would it be possible to repair the old grate or is there a good chance it will crack? I was thinking about bringing it to a forge!

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dcrane
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Post Tue. Feb. 12, 2013 9:25 pm

tcalo wrote:Would it be possible to repair the old grate or is there a good chance it will crack? I was thinking about bringing it to a forge!
repairing a warped grate is all but impossible and is generally only done when the part is simply not available (with chubby this is not the case... Larry is readily available to help you http://www.chubbystove.com/ )

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LsFarm
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Post Tue. Feb. 12, 2013 10:14 pm

Did you 'season' the grate before you built a full-heat fire on the grate?

It's generally a good idea to gently heat and cool cast iron parts a few times before putting them into full heat.

Cast iron has a lot of internal stresses, These stresses can cause warping if not gently relieved by the seasoning process.

And as mentioned above, make sure you don't let the ashes build up in the ash pan, blocking air to the underside of the
grate.. this insulates the grate from the cooling effects of the incoming air, and the grates overheat and warp.

Greg L
Burning Pea/Buckwheat through an antique stoker [semi retired SSboiler],
Running an Axeman-Anderson 260M boiler burning Pea, About 150-250#per day
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lobsterman
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Post Tue. Feb. 12, 2013 11:07 pm

It seems the grate was overheated somehow, from overflow ash in the pan as was suggested or otherwise. Time to visit Larry and get a facelift.

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tcalo
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Post Tue. Feb. 12, 2013 11:44 pm

LsFarm wrote:Did you 'season' the grate before you built a full-heat fire on the grate?

It's generally a good idea to gently heat and cool cast iron parts a few times before putting them into full heat.

Cast iron has a lot of internal stresses, These stresses can cause warping if not gently relieved by the seasoning process.

And as mentioned above, make sure you don't let the ashes build up in the ash pan, blocking air to the underside of the
grate.. this insulates the grate from the cooling effects of the incoming air, and the grates overheat and warp.

Greg L
I did not season the grate, first time I heard of this. Good info, thanks.
franco b wrote:Ash build up in the ash pan can overheat the grate.
As far as the ash goes, I've never had it high enough to affect the grate. If the ash got to that point then I emptied the ash pan after shaking down.

I'm hoping it was a fluke! I normally shake down and poke the coal bed from underneath until the bottom of the coal bed is completely glowing. I've been easing up on the shaking and poking hoping to leave a bit of ash on the grate to help insulate it from the coal bed. Trying everything I could think of, I don't want to warp another grate. Although the old grate is still usable!Thank you for your advice...much appreciated!

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tcalo
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Post Sun. Feb. 17, 2013 11:36 pm

Question about ash pans. I shake my stove down and leave the ash in the pan for about 12 hours. I empty the pan right before I shake the stove again. I don't think the ash could have contributed to the warped grate. It seems there is plenty of space for the grate to breath, but you never know! I was told to leave some ash in the ash pan to help insulate the bottom of the stove. Could I damage the stove if I leave an empty ash pan in it? What are your thoughts and how do you tend your stove?

buck24
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Post Mon. Feb. 18, 2013 12:45 am

Before I shake the stove down I empty the ash pan which has been in the stove since the last shakedown, about 12 hours. Been doing it this way for 34 years and never had a problem. Even when the ash pan is full there is still plenty of space between the grates and the ash in the pan. This should not effect the grates when you have space in between them.

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DennisH
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Post Mon. Feb. 18, 2013 5:16 am

I just had to replace one of the two shaker grates in my Yukon-Eagle Klondike furnace. The grate itself was fine, but the lug for the shake tool over time went from being square to somewhat diamond shaped, causing the shaker tool to stick on the lug. Not cool with a hot coal fire going. The other parallel grate also has a lug so shaking down wasn't an issue, but I thought it best to replace the grate anyway. Company was great. Got a replacement grate out same day. A custom craft blacksmith lives just a mile down the road from me. I may take old grate to him and see if he can heat and reshape lug back to a shape that allows shaker tool to fit on smoothly again.

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jjs777_fzr
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Post Mon. Feb. 18, 2013 7:10 am

As for seasoning the grate before going full tilt - here is a set of instructions I got when I bought some cast iron burn shields for my Upland - it goes something like this :

throw in electric oven set for 300F
after 20 min increase the temp by 25 degrees and then after another 20min increase by another 25 degrees
rinse and repeat until you max out the electric stove highest heat setting

At least that was the curing process I followed - not for the chubby but certainly not a bad idea for all things cast iron I suppose.

I've accidentally gone nuclear with my Chubby nearing 1000F or higher as measured by my IR Temp gun.
Not that I wanted it to go that high - but it has happened on more than one occasion where I leave the air and mpd open all the way while trying to get a reluctant coal fire going - only to realise it wasn't so reluctant after all.

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dlj
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Post Mon. Feb. 18, 2013 10:45 pm

jjs777_fzr wrote:As for seasoning the grate before going full tilt - here is a set of instructions I got when I bought some cast iron burn shields for my Upland - it goes something like this :

throw in electric oven set for 300F
after 20 min increase the temp by 25 degrees and then after another 20min increase by another 25 degrees
rinse and repeat until you max out the electric stove highest heat setting

At least that was the curing process I followed - not for the chubby but certainly not a bad idea for all things cast iron I suppose.

I've accidentally gone nuclear with my Chubby nearing 1000F or higher as measured by my IR Temp gun.
Not that I wanted it to go that high - but it has happened on more than one occasion where I leave the air and mpd open all the way while trying to get a reluctant coal fire going - only to realise it wasn't so reluctant after all.
I hear about seasoning grates fairly often on here but kind of wonder about the ability to do this in a home oven. Commercially there are a number of heat treatments that are done to grey iron (cast iron) with the lowest temperature process being stress relieving. A common stress relief cycle is to slowly heat the grey iron up to 900 to 1100*F, hold for an hour and then cool at about 100*F per hour back down to between 400 and 600*F.

I find interesting that your rate of temperature increase is roughly 75*F per hour, nice and slow which is good. But household ovens usually top out around 500*F. That seems pretty low for much of an effect on grey iron. I'm not saying it doesn't work, you are getting up hot enough to run into the tempering range for grey iron, so some kind of change could be happening. I don't understand what you mean above when you say "rinse"...

Also, just as an FYI- super critical annealing of grey iron is done up to 1700*F so running your stove up to 1000*F isn't doing much to the cast iron...

dj

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jjs777_fzr
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Post Tue. Feb. 19, 2013 2:15 am

dlj wrote:I don't understand what you mean above when you say "rinse"...
dj
rinse and repeat

a google search offers the following -->

It could have some sort of origin in the advertising of shampoo:

Lather, rinse, repeat is a phrase that is a common part of the instructions on shampoo bottles. It is sometimes also used as a humorous way of saying that a certain set of instructions should be repeated until an explicit or implicit goal is reached, or as sardonic commentary on some people's practice of taking descriptions, instructions or expressions literally and without common sense. Often the phrase is shortened to simply "Rinse and repeat".

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