Shippable cores

[briank]

I’ve gone back to the drawing board and based on a lot more research and experimenting I’ve created a shippable core “kit” that is more generic/universal.

I’m working on a batch box firebox shippable core kit that will utlilize three types of insulating material:
1) high temp high density insulating fire brick (cut from 24”x9”x2.5” slabs) for the first 9” of the walls that will be in contact with the firewood. It’s 4x as dense and resistant to abrasion as regular insulating firebrick but only loses about 1/3 of the insulation value as regular insulating firebrick, so itstill has insulating properties for the firebox but can withstand abuse
2) regular insulating fire brick (cut from 24”x9”x2.5” slabs) for the next 4.5” of the walls of the fire box, and
3) ceramic fiber board insulation for the roof of the fire box as well as the expansion chamber/riser combo.

The floor of the firebox will be 4 flat dense firebricks or Peter’s design, whichever the buyer prefers. However secondary air still arrives via a central channel in the ceramic board under the fire brick floor. 

I’m thinking of having a vacuum formed ceramic fiber shape made to cap the dense insulating fire brick walls in place of the 4.5” regular insulating fire brick (which is considerably cheaper but not as insulating as the ceramic board) as well as a vacuum formed ceramic fiber expansion chamber / riser that could be used with either a rear port, left or right sidewinder, or top port similar to Peter’s latest invention. So it will be generic enough to be used with the vast majority of current popular designs. That will depend on whether the final price per unit is somewhat comparable to building it out of ceramic fiber board by hand and/or making the last 4.5” of the firebox walls out of regular insulating fire brick.

Regardless I’m picking up a skid of the various bricks and multiple cases of ceramic fiber board insulation tomorrow so I can show what this type of shippable core kit will look like, what a handmade kit would cost, and what packaging and shipping will cost.

Also I’m getting 24”x9”x3” regular insulating fire brick that can be set vertical in a pinwheel fashion so that 4 bricks make a perfect 6” square vertical riser 24” tall. Add two more bricks, cut them in half lengthwise, and you’ve got a 36” tall vertical riser. Although with these new designs a vertical riser is no longer as important with batch boxes, they’ll remain so with J tubes.

If anyone has any input or constructive criticism, I’d really appreciate it. I’m going several thousand dollars in dept tomorrow to set up a rocket heater supply, probably on eBay, and I’m flying blind as to whether there will be a demand for these materials.

[briank]

Also I have a design and all the parts to convert one 55 gallon smooth sided drum into a full sized self contained 6” rocket heater using a readily available prefab door assembly that simply bolts to the side of the barrel. On a straight sided barrel there’s about 7” clearance (smooth sided drums are 34” high internally) between the riser and the inside top of the drum and the exhaust exits the rear next to floor level underneath the firebox assembly through a bolt on barrel stove flue collar. So the entire rocket heater will be self contained in one barrel with a shippable firebox and riser kit and bolt on door and flue collar and it will utilize more than 3/4 of the barrel’s total surface to radiate heat.

This unit will definitely be “portable” insofar as total weight will be less than 130 pounds. But the insulating fire brick are still fragile and would need to be disassembled and packed separately for transport.

[Orange]

Nov 16, 2017 17:33:31 GMT -8 briank said:

1) high temp high density insulating fire brick (cut from 24”x9”x2.5” slabs) for the first 9” of the walls that will be in contact with the firewood.

so you're not satisfied with the ceramic board lined with thin firebrick?

[briank]

Nov 17, 2017 2:49:43 GMT -8 Orange said:

Nov 16, 2017 17:33:31 GMT -8 briank said:

1) high temp high density insulating fire brick (cut from 24”x9”x2.5” slabs) for the first 9” of the walls that will be in contact with the firewood.

so you're not satisfied with the ceramic board lined with thin firebrick?

Honestly, no, not for longevity. It’s fine for short term but I have no way of knowing how it will hold up to years of use and abuse. 

My “partner” in all of this is a close friend, a retired engineer. We both use the same model of an excellent hybrid wood stove so we’re coming at this from long term use. His constant concern is that you can’t design assuming the end user will be careful and delicate with firewood placement. You have to assume the end user is just going to open the firebox door and throw/force wood in any way he can, and design for that. 

Plus, while it would have had a definite edge in insulation value, making the entire firebox out of a vacuum formed ceramic fiber shape was going to price this thing above a reasonable limit. And insulation value isn’t as important in the firebox as resistance to the forces of loading firewood so we’re saving it for the roof of the firebox and the expansion chamber/riser. 

[briank]

A skid load, 3/4 of a ton worth of various 24”x9” insulating fire brick slabs and cases of ceramic fiber board insulation, followed me home today. (More ceramic fiber boards and a 5 gallon pail of rigidizer - consisting of water glass, small ceramic fibers and a refractory binder - were already in the bed of my truck.) I’m going to have to sort everything out and learn how to use eBay, but at least now what was just an idea is taking concrete form.

An engineer from the ceramic fiber plant told me today that once the initial molding fees are retired, the price per unit of the vacuum formed ceramic fiber shape to cap the firebox and the separate expansion chamber/riser shape would be about the same cost as buying ceramic fiber boards and assembling them by hand, and would obviously save considerable time and labor. This is the first I’ve gotten that solid of a commitment out of them regarding cost comparisons between the two options, and it’s a good sign to continue to pursue that path in the near future. It looks like I’m going to follow that route. 

Anyone know a good tutorial for building an eBay marketplace?

[briank]

Getting closer. I expect to open a website and eBay store the first week of the new year. I have also sourced 30”x12”x3” or 24”x12”x3” regular dense firebrick to use to cap a masonry bell, and I’ll be picking them up at another factory on Tuesday, but the biggest ones weigh 86 pounds each, so I won’t be able to ship these via UPS like the shippable core kits. They’ll either be local pick up, or I’ll deliver them within a 250 mile radius of Altoona PA for a fee.

[briank]

I just registered the domain tonight, www.pennrocketheaters.com, and a friend is going to build the website for me over the next month and link it to my eBay store, which will go by the same name, Penn Rocket Heaters.

I’ve found a source for marine grade 316 stainless tubing and mounting brackets that are really going to simplify creating and mounting secondary air tubes.

I’m also eventually going to import firebox doors with glass and primary air vents that will really simplify that aspect of building a rocket heater, as well as cast iron cook tops.

[briank]

The 6” batch box shippable core kit will consist of 2/3 of the height of the left and right firebox wall, 9”, to be made from continuous 21”x9”x2 1/2” bricks of high density 2600•F insulating firebrick. It’s about 4 times stronger than regular 2300•F insulating firebrick and should withstand the loading of firewood in the firebox well. It will use regular insulating firebrick for the next 4 1/2” of the firebox walls. The rear wall will be 9” of the dense and 4 1/2” of the regular insulating fire brick. It will then use ceramic fiber board insulation for the roof. The port can be placed in a rear port, left or right sidewinder, or top (roof) port configuration.

You only lose about 1/3 the insulating value of regular insulating firebrick but this denser insulating firebrick has 4x the strength and seems strong enough for the left and right hand and rear walls and the port.

It will use regular dense non insulating firebrick for the floor though, as that gets the most abrasion and abuse from loading firewood. It seems a decent compromise to decrease mass and maintain insulating value for the firebox build . The upper walls and the roof maintain the highest insulation values for the rising heat inside the firebox.

The floor can either be flat dense regular firebrick splits, which is the best configuration for burning the flat bottomed compressed sawdust fire brick fuel I’m using, or the traditional PVDB “V” shaped configuration. The firebox will be 9” wide, 13 1/2” tall, and 18 1/2” deep (to accommodate 4 flat firebrick splits, a sill and a 1/2” gap to the firebox door.) The kit will NOT include the heavy firebrick for lining the floor. That can be sourced locally by the purchaser.

Roof can either be 1” or 2” ceramic fiber board. For a top vent, 1” might suffice, because the expansion chamber / horizontal riser will be built directly over the firebox roof. With a left or right sidewinder configuration the roof will extend over both the firebox and the expansion chamber/ horizontal riser which will be the same height as the firebox along the left or right side. The kit will include the expansion chamber / horizontal riser for all the configurations.

Secondary air will still be delivered via a recess in the ceramic fiber board under the firebrick floor. I’ve sourced marine grade 316 stainless steel tubing and mounts to make it easily attachable to a piece of metal plate between the ceramic fiber board under the floor and the layer of firebrick for the floor.

The expansion chamber/horizontal riser needs to maintain the highest temps so will be made of ceramic fiber board. It will be included unless the purchaser requests just the firebox.

Vertical 6” square risers can easily be constructed from 24”x9”x3” regular insulating firebrick arranged in a pinwheel fashion. Four bricks will create a 24” vertical riser, six will create a 36” riser, and 8 will create a 48” vertical riser. These bricks will be available separately

All of this kit will be robustly packaged to protect the fragile insulating firebrick and shipped in one box via UPS or USPS. Assembly will be simple with easy to follow directions.

Photos this week hopefully.

I’m still contemplating having a vacuum formed ceramic fiber shape made that would take the place of the 4 1/2” regular insulating firebrick wall extension and ceramic fiber board roof and serve as a cap for the HD 2600 9” walls. It would further simplify creation of the firebox but cost a lot of money up front for molding fees. I’m also contemplating having one vacuum molded ceramic fiber shape for the expansion chamber / riser.

At present the shippable core kit will not include these vacuum formed ceramic fiber shapes.

My website is not up and runnng yet, but will be www.pennrocketheaters.com and the eBay store will be Penn Rocket Heaters.

I’ll have a price with the week. I still have to sit down with multiple invoices and do the math. (Designing, building and experimenting was the easy/fun part! I’m not procrastinating, I’m just not a numbers person.)



Each of these cases on the bottom row contains five 24”x9”x2 1/2” or four 24”x9”x3” insulating firebricks: