Looking for acurate Rumford measurements

[seamad]

Re: Looking for acurate Rumford measurements

seamad,

would be interesting to share notes on this. I have been experimenting with different heat resistant mixes myself over the years. A lot of the stuff that is readily available in the US is just ridiculously expensive over here (or not available at all)

Casting the throat can be a challenge in itself. The best approach I have found so far is explained here:
Richards Rammed Earth
Just build the fireplace out of brick and make the curved section of the throat out of ferrocement (chickenwire and rebar)
A mix of 1:2 portland cement/plaster sand on three layers of chickenwire is surprisingly heat resistant.


I have tried this myself (adding 0.5 part lime putty to a 1:3 portland/sand mix to make it easier to sculpt) and so far so good.

Here is some research into the fire resistant behaviour of ferrocement:

https://www.doaj.org/doaj?func=fulltext&aId=1465260

here is another forum discussion about alternative throat designs:
Casting Rumford Throat - Masonry - Contractor Talk

As for casting, I have not tried this yet but three sources on the web seem to confirm that this is the best homemade recipe:
Homemade furnace refractories
Making DIY Refractory For Your Foundry Furnace.

2/1.5/2/1.5 (fireclay/portland/silica sand/perlite)

But, in the examples given (foundry from melting metal) this mix is cast into a container and the final form is thick and solid. The throat on a rumford has thin, curved walls, so it can't be to brittle.

I would probably stick with the ferro cement, or, add some reinforcing metal mesh to your casting.

Let me know how you get on.

Cheers,

thijs

Bit of a thread hijack sorry.
Had a look at the chicken wire method awhile ago and thought it looked pretty simple.
For some reason my IP address is banned for contractor talk and I can't sign up, have tried a few times ans sent them a coupke of emails with no response.
Just started cutting some bricks for my wfo. Haven't finished the new deck for them both yet, missus wants it done for xmas
Will keep you up to date.
cheers

[seamad]

Re: Looking for acurate Rumford measurements

9 posts and you know of my rough sketches? How bizarre....

A rough one then it is.....

I've been a' lurkin awhile.
Thanks for the sketch, like you sailor soldier one the best

[thijsatteiltje]

Re: Looking for acurate Rumford measurements

What mods ?
I'm planning on building an outdoor one, and will reduce the height of the opening slightly as per the rumford site.
Am also planning on casting my own throat and smoke chamber as postage to australia is exxy.
Would anyone with experience know what material would be best ?
Would a castable insulator be better than refractory material for example ?

seamad,

would be interesting to share notes on this. I have been experimenting with different heat resistant mixes myself over the years. A lot of the stuff that is readily available in the US is just ridiculously expensive over here (or not available at all)

Casting the throat can be a challenge in itself. The best approach I have found so far is explained here:
Richards Rammed Earth
Just build the fireplace out of brick and make the curved section of the throat out of ferrocement (chickenwire and rebar)
A mix of 1:2 portland cement/plaster sand on three layers of chickenwire is surprisingly heat resistant.

I have tried this myself (adding 0.5 part lime putty to a 1:3 portland/sand mix to make it easier to sculpt) and so far so good.

Here is some research into the fire resistant behaviour of ferrocement:

https://www.doaj.org/doaj?func=fulltext&aId=1465260

here is another forum discussion about alternative throat designs:
Casting Rumford Throat - Masonry - Contractor Talk

As for casting, I have not tried this yet but three sources on the web seem to confirm that this is the best homemade recipe:
Homemade furnace refractories
Making DIY Refractory For Your Foundry Furnace.

2/1.5/2/1.5 (fireclay/portland/silica sand/perlite)

But, in the examples given (foundry from melting metal) this mix is cast into a container and the final form is thick and solid. The throat on a rumford has thin, curved walls, so it can't be to brittle.

I would probably stick with the ferro cement, or, add some reinforcing metal mesh to your casting.

Let me know how you get on.

Cheers,

thijs

[brickie in oz]

Re: Looking for acurate Rumford measurements

That's an awesome looking fireplace. How deep is it ?
Any chance you could draw one of your rough sketches of the throat design ( a X- section ) ??

9 posts and you know of my rough sketches? How bizarre....

A rough one then it is.....

[seamad]

Re: Looking for acurate Rumford measurements

Here is one I built for myself at home last year, no fancy cutting in the throat, it draws like a beauty and kicks out tons of heat.
FYI the opening is 1600mm wide and 900mm high at the the top of the intrados.

That's an awesome looking fireplace. How deep is it ?
Any chance you could draw one of your rough sketches of the throat design ( a X- section ) ??

[seamad]

Re: Looking for acurate Rumford measurements

The entire Rumford design, both regular and modified can be built with standard firebrick, no need to cast anything.

For dimensions and design of both: Rumford Fireplaces

If I don't have a cast throat section then I'd need a steel lintel to support the bricks ? Haven't seen any all brick ones on the rumford site, nearly all are the bought cast sections and a few who have cast their own.

[seamad]

Re: Looking for acurate Rumford measurements

A modified Rumford has different firebox dimensions ( ie: deeper wider firebox
) than a true Rumford, which is tall and shallow in depth. But it is not built like most modern, cavernous fireboxes built today.

My idea was for a rumford 900mm wide, 800mm high and 400deep with a 400 wide back wall. How much can I deepen and widen it ?

[brickie in oz]

Re: Looking for acurate Rumford measurements

Here is one I built for myself at home last year, no fancy cutting in the throat, it draws like a beauty and kicks out tons of heat.
FYI the opening is 1600mm wide and 900mm high at the the top of the intrados.

[Tscarborough]

Re: Looking for acurate Rumford measurements

The entire Rumford design, both regular and modified can be built with standard firebrick, no need to cast anything.

For dimensions and design of both: Rumford Fireplaces

[stonecutter]

Re: Looking for acurate Rumford measurements

A modified Rumford has different firebox dimensions ( ie: deeper wider firebox
) than a true Rumford, which is tall and shallow in depth. But it is not built like most modern, cavernous fireboxes built today.

[seamad]

Re: Looking for acurate Rumford measurements

Rumfords are not really suitable for a true outdoor fireplace, although they work fine for a protected, covered outside area. Even then a modified Rumford will perform better than a true rumford.

What mods ?
I'm planning on building an outdoor one, and will reduce the height of the opening slightly as per the rumford site.
Am also planning on casting my own throat and smoke chamber as postage to australia is exxy.
Would anyone with experience know what material would be best ?
Would a castable insulator be better than refractory material for example ?

[Tscarborough]

Re: Looking for acurate Rumford measurements

Rumfords are not really suitable for a true outdoor fireplace, although they work fine for a protected, covered outside area. Even then a modified Rumford will perform better than a true rumford.

[stonecutter]

Re: Looking for acurate Rumford measurements

Hi all,



I have been experimenting with smaller Rumford fireplaces for outside and have
created a Rumford Calculator...........to help with different
sizes. I now realise the Calculator is probably off the mark
considerably.

That is because an outside fireplace doesn't function like an inside fireplace, because of the infinite variables which effect draw outside.

[thijsatteiltje]

Re: Looking for acurate Rumford measurements

Al,

fully agree with you. Sorry if I was not clear.

My intention is not to experiment with the design, just with building materials (as availability and price are a factor, plus it is fun to come up with something unique)

But I have searched high and low and it is very difficult to get clear, complete an unambiguous specs about the size, area and relations of the different components.

I even have the old Count's papers somewhere but those also require some interpretation.

Someone might mention he uses a throat that is 4 inches deep, but then fails to mention how wide it is (not to mention most throats are trapeziod shaped)

So what I am curious about, are the design specification for a Rumford based on airflow, pressure, expansion of gasses, venturi effect and how the column of rising gasses in the flue behaves.

Cheers,

Thijs

[brickie in oz]

Re: Looking for acurate Rumford measurements

If you have read about the Rumford design you know what is required to make the fireplace work.

Dont try to reinvent the wheel.