Alcosa forge dimensions

[Toadstone]

OllyO, I would do an internet search for "boiler treatment" to find some rust preventatives that can handle the kind of heat that the water in your bosch will be subject to. That should get you moving in the right direction.

 

Also, you could look at automotive radiator rust inhibitors like Water Wetter, for example. Please note that I have no practical knowledge about any of this - I'm just tossing ideas.

[OllyO]

Cheers Toadstone, I'll look into it.

 

I had a thought regarding the fake tuyere plate, it doesn't really need the steel plate, I could make a casting and then black it, I'm sure that'd do the trick alright.

[VaughnT]

How hot does the water in one of these systems get?  I realize the tue's end sticking in the fire is going to transfer a lot of heat to the tank, but wouldn't the mass of the water and steel radiate that heat away rather quickly?  Would it be worth while to add a set of heat fins to the tank to create more surface area to help dissipate the heat?  Or, a second tank of water to draw the heat out of the first?

 

Oily, do you think the casting would spall off during the heat cycles?  I'm curious as to how one might be able to go about it....  I definitely like the idea of a backboard of some kind just for aesthetics.

[OllyO]

I shouldn't have thought it would spall off.  The castable fire cement I use is produced by VITCAS in Bristol and they make all sorts of fire resistant stuff for foundries and the like.  I've used it alot in woodburning stoves, Rayburns, fireplaces and ranges with great success.  I know these appliances don't get aywhere near welding temp (1200?) but I'd imagine the back of the forge really doesn't get particually hot either, maybe max 150-200 degress?  That's an uneducated guess so please correct me.  I'd have to cast the stone in such a way as to allow some tolerance for the expansion of the tuyere etc but other than that I can't forsee any problems.

 

I really like the look of Mike's forges at Greystone forge and want to make something similar to the design of the back plates he makes.  There is a photo on the page below;

 

http://www.greystoneforge.co.uk/products/forges

 

In terms of the temp of the water, I've been told during long sessions you can get the water to boil but I have a large bosch so hopfully this will be avoided.  With regard to the reasoning of using a backplate or my need for one, it is as before, purely a matter of aethetics.  Daft really but I'm enjoying making this thing so may as well enjoy looking at it as well as enjoy using it!

[Dan P.]

Olly, a few things;

First of all, as far as treating the inside of your tue/bosh goes, I wouldn't worry about it, it'll be fine for years. My mate has a set up which is over a decade old where the back bosh is mostly made of fossilized rust and it's not a problem. The heavier gauge the better, but you cannot expect something that has one side exposed to white hot fire and the other exposed to water at a rolling boil to last forever. When it fails, you patch it up or replace it.

Second; Cast refractory has one main problem for our applications, which is that clinkers will stick to it and eat into it, and removing them can be destructive to the casting. Keep it away from clinkers, though, and it will be fine.

Lastly, concerning the dimensions of your hearth, I would suggest that it should be roughly the height of your anvil, and the hood should be as low as possible while still being able to see the heart of your fire. If you are in an open sided space, you might want to enclose it as much as possible, because if you have ever been camping you will know that wind will always blow smoke in your face and up your nose if you give it half a chance. To the same end, the higher the flue, the better.

[OllyO]

Picked up the blower today, plugged it in and it works!  It has a variable control on the switch board and also the remains of a slide valve on the blower itself.  It's an Alcosa F20M.  Seems to push out a lot of air.  Does anyone know the approx age of this unit?

 

 

[VaughnT]

Great find!  Can't say for sure, but it looks very 1950-ish.  Sure to be a great addition to your smithy!!

[Dan P.]

OllyO, I had a speed controller like your one, it had metal casing and no earth. It had been used continually for 60 years or more with no one getting zapped, but who wants to be the first? 

[OllyO]

I got a chance to give the blower and reg a good clean this evening.  It all looks to be in good nick.  I soldered/ heat shrinked all the terminals and gave them all a good clean.  I also repacked the bearings that were easily accessable.  I'll give it a coat of paint in the next few days.  Anyone know what colour this unit would have originally been?  It looks to have been black by my eye.  Seems fickle I know but may as well return it to the original colour I think.

I'm really surprised how much air this puts out, I suppose having never used a forge I've nothing to compare it to but it's a really powerful motor when run up fully.

 

Forgot to say, I also got the chimney that was last used on this forge.  There are a few sections that are knackered but I'll cut those out and weld it together.  Looks like I'll have a 4m stretch.  I know woodburning stoves need min 3.5m to run some where near right but is there a rule of thumb for a side draft?

[John B]

Hi Olly,

Are you getting confused between side draft and side blast?

 

Side blast is the hearths description, (or back blast)

 

Side draft is a flue that has an aperture at the base of the flue which sits on the hearth (plenty of examples if you use search) and appears to "suck" the flames and fumes into, and up the flue.

 

What you have is a hood and the flue sits on top of the hood, 4M should cope well, so long as the top is at least a couple of feet above the roof it should be fine, the higher the better, and clear of roofline apex and other obstructions which could cause turbulance also helps. Once the fire is going, it should draw well.

 

You do not say what diameter the flue is, many were 6" or 8" diameter, 10" to 12" is more preferable.

[OllyO]

Yep, my mistake John, there are so many new terms drifting about in my mind I'm liable to get muddled from time to time!  I just went outside to check the flue and it's a bit of an odd one at 9".  When I measured the top of the hood (flat area where collar for flue is) it seems as though my forge built to the original dimensions couldn't take a flue exceeding 9" so this seems right but I've only ever seen flue supplied in increments of 2. 

 

Just checked the top section with the rain cowl on and found that to be 10".  Hmm.  May just have to bodge that on as it's the piece in best condition.

[John B]

Yep, my mistake John, there are so many new terms drifting about in my mind I'm liable to get muddled from time to time!  I just went outside to check the flue and it's a bit of an odd one at 9".  When I measured the top of the hood (flat area where collar for flue is) it seems as though my forge built to the original dimensions couldn't take a flue exceeding 9" so this seems right but I've only ever seen flue supplied in increments of 2. 

 

Just checked the top section with the rain cowl on and found that to be 10".  Hmm.  May just have to bodge that on as it's the piece in best condition.

The original was probably 8" diameter, if you need to fit larger all you need to do is to remove the top register plate and lower the overall height by cutting off the top edges until you get the aperture size you require, then make and fit a new register plate for the new flue.

[OllyO]

I've nearly finished the forge now so I've started work on the shed.  I've been looking at how to seal the flue where it punctures the roof and come across these silicone flashing/ gators;

 

http://www.ebay.co.uk/itm/130793372020?var=430103232927&ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

 

My ceiling height is around eight foot so it's a good few feet above the hood of the forge.  What do people reckon, do I need the high temp one or the low temp?  I'm running a very tight budget so if I don't need the more expensive one I'd rather not buy it.

[OllyO]

PS>  Also, is there any reason why I can't join the blower to the air pipe at the rear of the bosch with some radiator/ water hose from a car? 

[Alan Evans]

PS>  Also, is there any reason why I can't join the blower to the air pipe at the rear of the bosch with some radiator/ water hose from a car? 

 

Ha Ha! I don't believe it!

 

I started reading your thread this morning and thought Blimey! deja vu! You have been reproducing my first hearth building history to the weld fillet!

 

The only thing I thought I could add was to tell you that I had a remote bosh made up from a 25 litre oil drum with some Morris 1000 1/2inch bore heater hose connected to a blanking plate on the back of the tue and the air blast was connected with a bit of vacuum cleaner hose....and then I read your afternoon post`!

 

The answer to your question is there is no reason why you can't, it works okay-ish.

 

I have not understood how you are making the bosh / tue connection. If you do that with rubber hoses like mine....the water flow went from the bottom of the drum to the lower connector on the tue and the return went from the upper tue connector to a copper tube which hooked over the top of the drum. It used to boil like crazy on a good day but I found I could unhook the return and drain a bit of hot water out and refill with cold.

 

I tried anti freeze to start with but it got expensive when it boiled away. I did have the pipes freeze a couple of times, the first time I only realised that had happened after the tue water boiled and blew the pipes off! I used to unhook the return pipe and drain it out if I remembered in the winter.

 

My tube and hosepipe tue lasted for a good few years. I think the tinplate oil drum bosh lasted as long, five or six years at least of full time operation. I eventually replaced it with a bottom blast hearth which I built with a long bed so I could heat 600mm lengths when I got my power hammers.

 

The sheet work of the hearth lasted over ten years and I eventually rebuilt it with stainless steel and that is still going on 20 odd years later...still using the old original Alcosa back frame angle irons!

 

The fire back I use is a bit of 25mm mild steel plate. I would not waste time with the castable.

 

The tue was set high so its air pipe was at the level of the hearth sides. The bed of the hearth was a mix of earth and ash the whole box was filled to within an inch of the top edge but formed a mound above the level of the air pipe in the centre, with a "swans nest" bowl scooped out to contain the fire. An arc of wagon tyre was laid across the front to create a removeable coke retainer and was a solid rest for hearth tools.

 

If you have the tue set low it means you have to have an unecessarily huge fire to heat the middle of a long bar. Setting it high obviates the need for the removable side plates...which if used invariably mean half your coke goes on the floor!

 

As others have said the tue only needs to poke into the hearth enough to keep the fire a bit forward of the back plate say 150mm at most on that size of hearth.

 

I was looking for a drawing of the configuration of the hearth that I copied originally, have not found it yet, I will do a sketch for you if it is not clear from my description. 

 

Alan

[Alan Evans]

I've nearly finished the forge now so I've started work on the shed.  I've been looking at how to seal the flue where it punctures the roof and come across these silicone flashing/ gators;

 

http://www.ebay.co.uk/itm/130793372020?var=430103232927&ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

 

My ceiling height is around eight foot so it's a good few feet above the hood of the forge.  What do people reckon, do I need the high temp one or the low temp?  I'm running a very tight budget so if I don't need the more expensive one I'd rather not buy it.

Definitely the high temp one out of those, but I certainly would not buy one. I have always made my own out of aluminium sheet (reclaimed from a caravan)... cut out a 25mm undersized hole and turned up the flange with a mallet. You can also make or buy a clamp on rain-collar but given the open shelter it is in it is probably not necessary.

 

Alan

[OllyO]

Thanks for getting back to me Alan.  I've attached a photo of my bosch tue below.  I originally intended to have it bolt together so the bosch and tue were seperate but the general consensus was that they have approx the same life span so there was no need.  Sadly I'd already welded on the tue on recommendation from some people locally before getting all te responses on here regaridng it's length.  I'll either have some spacers turned up by my neighbour or do as John says and made up an angle iron shelf for the bosch to sit on so it's adjustable.  I fitted a little drain valve yesterday that I got from screwfix for a few quid.

 

 

 

You can see the air pipe protruding from the back of the bosch, that's where I want to use automotive rad hose to connect it to the blower.  There's a place locally that makes up hose with any bends and flares etc.

 

I decided to run with the castable idea.  I can't afford steel to buy steel in 10mm plate let alone 25mm.  Minimum order size is 1m x 2m sheet and I've search the local scrap yards already.  I've used this castable a lot and it is very good se we'll see how it stands up.

 

 

 

The blower and reg have been stripped back and primed ready for painting.  I've welded in some frame around the old (way too big!) cut aways so now there is a steel plate that sits behind them and blanks them off completely.  I will then cut a cut away in this plate as and when I decided upon a good size.

 

[Alan Evans]

Looking very professional...almost like a real one!

 

You could just mount the fan directly onto the bosh, either just bolts through the tank wall and cut off the pipe flush or weld on a plate to the end of the air pipe, any particular reason why you are thinking of rubber?

 

The advantage of having a slide valve somewhere between the fan and air pipe is well worth the time to make one up.

 

I have one of those lovely old rheostats as well, identical, I make up electronic controllers now, but it is still in the shop as a standby. The only things I have done to my F20M over the 35years I have had it (bought second hand from a school) is about ten sets of brushes and a pair of bearings. Be careful that you do not over grease the bearings, I had to have my 35hp hammer motor rewound due to over zealous greasing! £600 of Ouch!

 

The big advantage of using a bit of flexible tube for your air would be to put the fan in a box to cut down the noise. Makes a huge difference. I now use my F20M for my gas furnace and have put it in a box with an offset air inlet and connect to the burner with a vacuum cleaner hose.

 

I just happened to have a bit of 25mm plate offcut which I propped up for the fire back. but I think that arrived a couple of years after I had started using the hearth. The Alcosa cast "cape" was higher and narrower than yours, but they were only fitted to the 36'' square hearths AFAIK.

 

We had a saying around here along the lines of "anything'll do, nuthing wunt" go with what you have!

 

Alan

[OllyO]

Thanks again Alan, good to here the F20M is still in action.  The whole set up seems to be really sturdy in construction.  The shed that my forge was in rotted away around it, the blower/ reg had been used for well over ten years when I got it and had been left in this rotten old leaky shed.  I plugged it in and away it went.

 

The reason I wanted to use flexible hose was becasue I'm going to mount the blower below the bosch between the diagonal braces on the legs of the rear of the forge (not sure if that makes sense.  This means the tube will have to do a a 180 to reach the tube in the bosch.  Becasue the forge is in an open sided structure I want to keep the blower tucked away, I'm also short on space.  

 

Forgot to mention, I've already made the slide valve from the remains of the original seen in the first picture of the blower.

[Alan Evans]

I have just revisited your earlier images and note the direct bosh tueyere connection I managed to overlook before, sorry.

Every time you put a bend in the pipe you restrict the flow so the slower the curve the better.

For very similar lack of space reasons to yours I mounted my fan on the back of the hearth with the motor tucked underneath and the air delivery pointing up which meant only a 90 degree bend if I remember correctly. The slide valve was bolted to the delivery flange of the fan with an extension handle to bring it out to the side of the hearth, and I made a sheet metal funnel reducer to the diameter of my flexible pipe and another to reduce down to the air pipe.

My first forge was in a 3.8 x 2.8 metres (12' x 9') od shed which was extended to 3.8 x 4.4 (12' x 14') when I put in my second power hammer. Talk about tight squeeze, it finally had three power hammers a treadle hammer which could be swung over the 3cwt anvil a hulking great 5+cwt anvil and an old cast iron pillar drill apart from the leg vice tool racks and hearth! On the 50kg Reiter and the 1cwt Alldays I was standing out in the rain if I was forging anything over a metre. Happy days!

[OllyO]

It sounds like we really are on the same tangent.  I've made a funnel to reduce diameter off the slide valve to the 35mm OD pipe I'm using for the air.  My  flexible hose (wire reinforced) has to do a 180 degree loop though.  The shed I built had a roof coverage of 14ft x 12ft, looks to be a handy size.  I've only got an avil and a small leg vise in with the forge though so sounds like I've got a little more room to manouver than you!

 

Here's tone half of the slide valve ready to be painted (excuse the welds, low on gas) and below is the forge as it stands.

 

 

[OllyO]

Here's the reg plate as well,  I made a flange for it so I can seal the flue with rope.

 

[Alan Evans]

I will send you some photos of my Mk. 3 hearth. It is now used mainly to support my gas furnace. It has hinged flaps hanging off the hood which reduce heat and fumes from big fire. I was always on the lookout for a glass oven door to hang off it so I could see through. A tinted one would be best if it could cut down the glare. I will sketch a really handy stand which I copied from Ivan Smith's hearth. it hinged up off the hearth with a loosely atached prop  which could take up any height, great for longer bars. The only thing I would do with your hearth is to lift the tuyere so the hot spot of the fire is in line with the  top edge of the tray so you can heat the middle of the bar without taking out those beatifully made but horribly impractical panels on either side. You will need either some castable /fire bricks or my earth and ash mix under the fire. Whatever you go for you will need something to create a "swans nest" to contain the fire. You can imagine if the tray is just full of coke the fire will just keep moving around and spreading out across the whole hearth.

 

Alan

[OllyO]

Cheers Alan, any infor would be greatly appreciated.  Who'd have thought a tray with a fire on could be complex?!

 

Unfortunatly I can't move the tuyere up as the hole in the back of the forge has been cut as has the back plate.  I'll give it a try and see how it goes.  The doors on the side are now essentially redundant as I've made some panels to go inboard of them.  When the doors are dropped it reveals the panels that at present have no cut out cut into them.  Here they are from inside the hearth;

 

 

Here's the blower, slide valve and funnel bolted onto the forge.  I've got a length of pipe ready to connect this to the air tube on the back of the bosch once it's mounted.

 

 

 

 

 

I've lined the bottom of the hearth with some vermiculite board stuff that is used in woodburning stoves.  It's a bit broken up but looks alright to me.

 

My shelter is finsihed so I'll move the forge in tomorrow and fire it up all being well!

[Alan Evans]

I was given the remains of Alan Knight's hearth when we moved the forge to Hanbury. He bought a new one and the first thing he did was cut a new hole in the back plate and raise the tue up.

 

I am really sorry I did not start reading your thread until you had already got so far and can well understand your reluctance to ruin your lovely metalwork on the word of some faceless cove on an internet forum. Alcosa have always made them to that design I can't understand why they never changed, presumably most of their customers have coped!

 

You can always do it later if you find it a problem! If most of your work is on the end of bars you may never need to get at the centre. You can just log my configuration away in your "to solve a future problem compartment"