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View Full Version : To Ed T and OP ...stove spark question



Dave R.
03-21-2005, 12:49 PM
Hi Ed....just got back from the North East Rondy and thought I'd hurl you a question. Several guys including me and OP got some more pin holes on this trip, even with screens in. I know you guys have thought about this and you have a good answer.....what about putting a spark arrestor on the top of the stove pipe too?? Your thoughts?

Dave

Ed T
03-21-2005, 01:31 PM
Dave,

A spark arrestor on the top of the pipe would probably help, but my experience with any type of screen on top, is they soot up much faster because it is cooler at the top of the pipe. On a Para Tarp or Para Tipi, not much problem to clean, except for having to go outside. On any of the bigger tipi's, pretty much impossible to clean without taking the pipe out.

What kind of wood is giving you the most problem?

My thought is to try a solid metal disk with some 1/8" holes in the bottem slot and the regular screen in the top. You might have to play around a bit so you don't smoke your self out. If you want to send me an e-mail with your address and which size stove you have, I will make one up for you.

I get pin holes ocassionally and just smear some silicone on them one a year or so.

Ed T

razorsharp
03-21-2005, 01:38 PM
You'll get less sparks if you stoke gently.

Woods Walker
03-21-2005, 02:56 PM
Donít put an arrestor on the top. It just clogs. I have tried it with the stove outside of the tipi (I only test things out outside of the tent incase it does not work). I can tell you one thing. A stack robber does kill almost all sparks without screens. I have tested one and had zero sparks with pine. With a screen I donít believe any would ever come out. Iseen none. I made one out of stainless today in the shop and tested it. ZERO sparks. But it is 4 inches wide and 9 inches long and comes in at about 10 oz (22 gauge stainless). This thing works very well. The heat output is fantastic. The stove was red; the stack robber was red even with coals only. The pipe had no flames and during high burn was only red for about 14 inches or so. But I donít know how it would work with other size stove or any pipe above 5 feet. Updraft was good. Razorsharp I tried to make the thing spark and got nothing. I stoked it hard. Everything.

Dave R.
03-21-2005, 03:26 PM
Hi Ed...the wood I used was mostly hardwood a little evergreen to get started...I think the pinholes came on the first night when there was no wind at all...not even the slightest breeze. I have a metal disk that I made for my stove years ago that has holes in it just as you mentioned. I was using it to slow down the burn out west when I was burning western pine. I had it last weekend but I didn't use it because I didn't think I needed it. Never gave much thought to helping to arrset sparks. I don't mind the pin holes...after 8 years, I have had very good luck avoiding them, just trying to figure out where I had trouble this time...I'll give my disk a whirl...I think I may have been getting lax also too, and leaving both screens out during the start up to encourage a strong updraft...that could be where I went wrong too....by the way , mine is one of the old stoves and stove pipes...I don't think you manufactured it. Thanks for your time Ed. Thanks also WW and Razor..

Dave

Dave

razorsharp
03-21-2005, 03:29 PM
What's the principle behind the 'stack robber'?
Never heard of it. Thanks rz

Woods Walker
03-21-2005, 03:49 PM
Razor a Stack robber or Heat exchanger works by direction the heat back into the stove and the exchanger itself rather than letting the heat energy escape up the pipe. The fact that it eliminates sparks is do to the intense heat and the inner plate of the exchanger. The one I made looks like a tub with a flat top and a hole for the pipe. Inside about mid way is a plate in the center and on the ends of the plate for about 2-3 inches on each side is stainless hole stock about ľ inch holes. This allows the smoke and fumes to escape up the stack. However any sparks bang against the center plate, the sides and the ľ inch holes. They are broken into nothing. The Kifaru collar and spark arrestors get anything missed. But I think only one spark arrestor is needed. Also I have only tested it in my (what has been called ďround stoveĒ). Basically it is a baffle that a person can decide to take on a trip or not. Baffle in a stove does much of what a stack robber does. I will send a pic of the robber in a few weeks when it is in action on opening day (fishing trip).

razorsharp
03-21-2005, 04:06 PM
I got ya...interesting. I've been wanting to try a single spark arrestor that sits diagonally inside the stove pipe. It would be longer, and maybe slightly thicker, and oval shaped, but would present a barrier for sparks to run into yet the smoke would zig-zag through. Of course some sparks would too...or maybe all would?

Woods Walker
03-21-2005, 04:16 PM
Nothing beat the robber for killing sparks. All of these things reduce updraft but the robber makes up for it with a big increase in heat so even if the stove runs slower the combustion is better. I just donít know how it would work in a bigger tipi or stove. The stove gets super hot and the robber does too but the pipe can be touched with your fingers 3-4 feet up during a good burn. In a bigger tent would a much hotter stove and the surface area of the robber make up the loss of the cherry red stovepipe? Some people like to see the flames shooting out. That too is mostly lost with the robber.

Dave R.
03-21-2005, 04:32 PM
WW...would appreciate seeing a pic...how much does it weigh??

Dave

Woods Walker
03-21-2005, 04:59 PM
I think the thing comes in at under an lb. I busted my digital camera so that pic will have to wait until I get another one (soon) Maybe 26 gauge stainless would make it even less. But 22 are all I have. I donít see a way to collapse it down. But that is not an issue for me as I made it to fit inside the round stove. The extra 10 or so oz wonít be an issue to me as the stove seemed to run longer on the same amount of wood. Less work. I donít think the extra heat would harm my small stove. Might make some more warping but with the rods the stove comes into shape anyway. Patrick may have done some work with a robber. After all someone said he worked on an oven. Why not a heat exchanger? I would be interested in finding out if he tried such a thing. I only have experience with alcohol stoves and hobo wood stoves. My round stove worked out great but even with a heat exchanger I could only see it being able to do no more than a 6-man tipi. There is no way a person could carry a non-collapsible stove for a big tipi. Mine comes in at 10 oz more than my small stove. If it was bigger the disparity in weight and size would get more extreme, He has been working at this lightweight wood stove thing for a long time.

OP
03-21-2005, 06:02 PM
Hey Dave,
upon breaking my stove down sunday I noticed there was about a 1/4 inch gap between the end of the spark arrestors and the back of the stove pipe. Apparently they were not 100% slid in.I could see how sparks could sneak through that gap.
The problem I think is the stove collar.The thin slots where you insert the screens bind down on the spark arrestors(this is evident because it is difficult to slide the screens in and out freely).This can make it difficult to get the screens COMPLETELY in to the back of the pipe.Even though they feel pushed in there is no way of knowing. The weight of the pipe on the collar is the culprit of binding the screens.I noticed the ends of my screens have bent and broken wires which can cause agap and binding
I realize no one is getting the amount of holes I am but I'd bet some of they're occassional holes are showing up at once because the screens aren't in 100%
I hope this doesn't come across as a slam on the tipis because it's not. I love my tipi and stove but I need to figure out why Im getting so many holes.
Dave, had agreat time over the weekend met alot of nice people. Looking forward to the next one /images/%%GRAEMLIN_URL%%/wink.gif

Ed T
03-21-2005, 06:15 PM
OP & All,

The collars for about the last year have slightly wider slots so the screens are easier to insert. Make sure the screens are as straight as possible as well.

Woods Walker
03-21-2005, 06:40 PM
You are in luck Dave. My Sister took a pic today afer I finished the thing. I didn't even know she did it. So take a look.

http://images5.theimagehosting.com/Jay_stove_2.th.jpg (http://server5.theimagehosting.com/image.php?img=Jay_stove_2.jpg)

Click on the pic to see it better.

Dave R.
03-21-2005, 07:07 PM
Right back at Ya OP!!1 What a great weekend!! Maybe Ed can send you a collar with bigger slots??

Dave

Dave R.
03-21-2005, 07:10 PM
WW....wow that's something!! Thanks! Now that I see that, I remember seeing something like this...a small square box that fits between two pieces of pipe...some stove comapny sells it...Dave

Woods Walker
03-21-2005, 07:58 PM
Op--Kifaru told me that new spark arrestors $5 each. Add $7 shipping to that. Maybe you should get a new set. The only time I got a pinhole was my fault. I started the stove without the screens. I have never had any issues with the collar and screen I got from Kifaru. Also I think keeping two in at all times is the best way to go.

Woods Walker
04-04-2005, 07:36 PM
I have an update on that heat exchanger. I used it this weekend in my paratipi. It rained very hard and we had wind up to 45mph. In fact the wind was so bad I had to readjust the pegs on the paratipi. That is saying a lot considering that the tipi is so darn stable. I had ZERO smoke. The wind was not able to create a downdraft though the exchanger to push any smoke out of the stove. I ran it without any spark arresters. During a low point in the storm I had my camping buddy stir up the stove real hard. He did everything possible to create sparks. Nothing was seen. Not one spark. The exchanger stayed cherry red even with just coals. I got a new record temp of 160 before I had to vent it out. That was with the wind blowing like crazy.

Dave R.
04-04-2005, 07:44 PM
Woodswalker...that's really saying something. You have really proven this. You do have me thinking!! Dave

Dave R.
04-04-2005, 07:49 PM
WoodsWalker...have you tried your contraption on a kifaru stove??

Woods Walker
04-04-2005, 08:18 PM
Dave,

Not yet. That weekend my small kifaru stove was doing a very important job under a tarp. Cooking pork tenderloin. I will have to test it outside of the tipi using my small stove. I like the shelter too much to risk anything happening to it. I canít see any reason why it would not work on the small stove. I am very excited about the exchanger. The heat increase was super. It burned trash wood down to nothing. Not having to fool around with the spark arresters is big too. I donít see any reason for them anymore. I tested the wire spark arresters compared to just the heat exchanger. Lots of sparks during a hard stir of the coals compared to zero sparks. But then again the holes on the sides of the inside plate on the exchanger are not much bigger than the stainless wire stock gaps (I took it apart and rewelded smaller hole stock to remove the need for the wire ones). The only difference is that my hole stock is welded to the sides so there is no chance of anything slipping though. I am starting to look at the 6-man tipi. I will not need to buy a medium stove for it. I will just need a longer pipe for the small stove. The only downside is that the wire screens weigh next to nothing and my exchanger is about one pound. But on the plus side I can boil two GI canteen cups (one on each side) on the flat top of the unite. It boils super fast. The exchanger did not get clogged up. I used the very worse wood I could find. The holes are just the right size so it is hard to clog. The heat inside is so intense that there was not even a bit of ash. It all got vaporized to nothing keeping the holes free of build up.

Woods Walker
04-04-2005, 08:21 PM
Dave I will photo the thing running when I make the photos of the HOBO stoves later this week or early next week.

Woods Walker
04-13-2005, 07:33 PM
Sorry this took so long. I deleted the photos of the thing running. I will take more next time I set the tipi up. But it did find some photos of the building of the heat exchanger. You can't see the baffle plate do to the angle but will see the spark arrestor part. These photos are before I cut the holes for the stove pipe, stove etc and welded the end cap on.

http://images5.theimagehosting.com/exchanger1.jpg (http://www.theimagehosting.com)

http://images5.theimagehosting.com/exchanger2.jpg (http://www.theimagehosting.com)

http://images5.theimagehosting.com/exchanger3.jpg (http://www.theimagehosting.com)

http://images5.theimagehosting.com/exchanger4.jpg (http://www.theimagehosting.com)

http://images5.theimagehosting.com/exchanger5.jpg (http://www.theimagehosting.com)

http://images5.theimagehosting.com/exchanger6.jpg (http://www.theimagehosting.com)

Dave R.
05-19-2005, 03:39 PM
WW...have you tried one on your kifaru stove yet??

Dave

Dale Lindsley
05-19-2005, 05:49 PM
Woods walker: Not to be an alarmist, but when using the stack robber in a tipi you might want to keep a sharp eye out for burning soot flakes. Cooling the smoke may lead to condensation in the pipe ABOVE the spark arrestor. These flakes may eventually catch fire and exit the stack, causing nasty holes in the tipi. I had this happen to me in my paratipi when I shut down the air to the stove for a while. Luckily it was raining so I just got big (1/2 inch square)black smudges on the tipi instead of holes. A good hot flame out the top of the pipe has some advantages.

Woods Walker
05-19-2005, 07:23 PM
Does not happen Dale the pipe is still over 600 degrees up to 3 feet above the robber. I have burned with this robber 40 times (testing) and 9 times in the tipi for long periods with every type of wood. There was no more ash build up than with the screens. In fact there was less. For condensation the pipe was just too hot but then again I looked at the pipe the next day.I believe that zero condensation (I never even thought to look for that) and the low ash was caused do to the superior combustion from the super heated firebox and the insanely hot heat exchanger. Shutting down the airflow is not the same thing as the stack robber as the updraft is no more effected than with a spark arrestor screen. Only the down draft is reduced do to the baffle. Tested in winds of 40 mph. I have never had anything come out of the pipe in the form of burning ash and almost no sparks. I can still see small flame coming out of my 5-foot paratipi pipe (I got one with and extra foot) when I burn dry small hard wood sticks. The reason is that I made the robber to not reduce the airflow too much. I donít get the dragonís breath flame and the pipe is cooler above 3 feet. My original exchanger did cool down the pipe more but the reduced airflow was something that I didnít want. The original one is of mild steel up against the white wall.

But thanks for the heads up.

Dave R.
05-20-2005, 06:41 AM
WW..any chance of making something like that smaller, and lighter, maybe collapsible, out of stainless steel?? You know....kifaru style, feather wieght......

Dave

Woods Walker
05-20-2005, 02:41 PM
I was thinking about it. This weekend I am going to work on a collapsible HOBO stove. What makes the stack robber a good spark arrester is the screened sides. If it were not wedded then the metal would warp leaving gaps and allowing sparks I would have to come up with something else. Maybe use the collar and screens I got from kifaru above the baffle. Even if the box did warp the baffle should act to retain the heat and kill lots of sparks. The kifaru screens would get the rest. Maybe something to work on. But making it too small would slow down the updraft. Something I didn't want to do.