Denver Q&A

How much will it cost to build the Denver?

What kind of simple trottle and reversing valve do you suggest to upgrade this loco?

What sort of grade is this loco capable of?

Can Denver be built to 32mm gauge (0 gauge)?

I've used 'silver-bearing' solder, but I've never used real silver solder. I know that my hardware-store propane torch will be inadequate by itself for heating the boiler parts, but would I be able to heat up the copper sufficiently for silver solder by using a tank of MAPP gas on the burner head?

Do the drawings show an option for a double acting engine and a throttle?

What types of reamers and taps are needed?

How necessary is it to have a water glass and pressure gauge on small scale locomotives?

The engine shown on sheet #4 of the drawings has an engine block and a separate cylinder. Can these two parts be soldered together with soft solder, or must silver solder be used?

How does a person hold all the parts together to solder them up?

Any ideas on making the boiler ends...would think they should be rounded out?

How much will it cost to build the Denver?

This is difficult to say. It depends a lot on what you already have by way of materials and machinery. If you have to buy a lathe before you can build it, it will cost a lot. However, if you are already tooled up and have a pretty good scrap bin, then it shouldn't cost too much at all. At a guess, if you have tools but have to buy all materials, gears, wheels, safety valve, etc., the cost will be perhaps $150 or so. (12-2-01) (Back to top)

What kind of simple trottle and reversing valve do you suggest to upgrade this loco?

Jim Reyer built a throttle for his engine. It is basically a needle valve mounted on a banjo fitting that attaches to the boiler at the rear where the steam line comes out. A reversing valve for the existing design would be much more difficult. To reverse an oscillating engine, you must exchange the steam admission with the exhaust. This is commonly done with a rotary valve (as on a Mamod), but our design did not include one for the sake of simplicity. If you used a fixed-cylinder engine with a valve, you could easily incorporate a slip eccentric into the design, but, again, our design did not include this. (12-2-01) (Back to top)

What sort of grade is this loco capable of?

Probably 2% - 3% with a light load. (Back to top)

Can Denver be built to 32mm gauge (0 gauge)?

I think it could be done. You'd need a narrower channel. The channel specified is square and I don't know if you could find a rectilinear channel of the proper dimensions. The alternative would be to cut the middle out of the larger channel and put it back together with a small plate at either end held on with some screws. You can cut the channel on the table saw if you have a carbide blade. It's nasty, but it works.

You'd also have to remove the sprockets and chain between the axles from the inside of the channel. They could be moved to the outboard wheels, or you could just abandon them and have two-wheel drive. We haven't tried this, so don't know how it would work, but certainly the engine should power itself on just two wheels, and may pull a short train as well. (Back to top)

You'll need to use real silver solder to do the boiler properly. I don't have any experience with MAPP gas, although I've heard that it burns pretty hot. I've also heard that you need a special torch head for MAPP cylinders -- you can't just use a propane torch. (Back to top)

I use acetylene, with a tip about as big around as my index finger. Before that, I had a torch from Sears called "The Hot One". This is just a propane torch but somehow burns much hotter. It has a stainless-steel tip on it that gets red hot. It might be hot enough for a small boiler like this. Another alternative would be to get two or three friends, all with propane torches, to help you heat the boiler to red heat. You'll be astonished at how much heat is required to bring the copper to the proper temperature, but you must do it -- any less just will not work. (Back to top)

Do the drawings show an option for a double acting engine and a throttle?

No. As designed, the engine has no throttle and, to keep it as simple to construct as possible, we have only included drawings for single-acting engines (two different ones are included). However, both a throttle and a double-acting engine could be used, with a little ingenuity. (Back to top)

What types of reamers and taps are needed? In checking a catalogue for industrial supplies for these tools, I discovered that there are straight shank, straight flute reamers; straight or spiral flute chucking reamers with a 45 degree lead chamfer; HHS drill length reamers with straight shank and straight flute; combination drill-reamers; chucking reamers with taper shanks; hand reamers; and, finally, taper pin reamers with 1/4" taper per foot. Which type is appropriate for the project? Likewise there are standard hand taps; spiral point hand taps; spiral point taps; combined tap and drills; fluteless taps; screw thread insert taps (STI); hand taps penta blue-style; spiral point taps-penta gray-style; Greenfield gun taps for through holes; Greenfield fluted taps for blind holes. Again, which is the correct style for the project? As is probably quite obvious by now, this is my first metal project of any kind, but I have to start somewhere.

For reamers, you'll want a straight shank, straight-flute reamer. Most reamers I've seen have a chamfer to help them into the hole. Most low-cost reamers (all you'll need here) are made of HSS (high-speed steel).

For taps, you'll want standard hand taps. Taps generally come in three varieties for any given thread -- taper, plug, and bottom. If they aren't specified, they're probably plug, which is fine. A taper tap tends to get into the hole a little easier. A bottom tap is for making a fully formed thread all the way to the bottom of the hole. A spiral-point tap is nice, but not necessary. With a regular tap, the tap must be backed off a little every half turn or so to break the chip. A spiral-point tap can be turned right in without backing off, as it pushes the chip ahead of it. This is fine for through holes, but with blind holes, you may end up with the entire chip stuck at the bottom (which may make no difference). A general rule of thumb, especially for beginners, is to buy cheaper, import tools. These tend to be general purpose, are made to reasonable tolerances, and will last a reasonable amount of time. You can always upgrade later when you are more experienced and know more. (Back to top)

How necessary is it to have a water glass and pressure gauge on small scale locomotives? I've noticed many locos, including Denver, do not have them. Yet a friend, who models in larger scales, feels they are indespensable.

On larger-scale locomotives, I would definitely agree with your friend. However, on small engines, especially simple ones, these amenities are not as important.

The Denver, and other simple engines, run at relatively low pressure -- usually under 40 psi. Most pressure gauges, especially miniature ones, will not read accurately in those low ranges anyway. Also, the copper tubing out of which the boilers are made has a built-in safety factor of several hundred times, so even if pressure did rise above design specifications (which it won't if you have a good, working safety valve), the engine is still safe.

A water glass, while useful, is also not necessary on small, simple engines. On an alcohol-fired locomotive, the biggest risk you run by running a boiler dry is damaging the paint. An alcohol fire is not anywhere near hot enough to damage a silver-soldered boiler. An engineer worth his salt will not let the boiler run dry anyway, because he'll keep a constant eye on the engine. When it stops, you blow out the fire.

With practice, you learn how the engine behaves given various internal conditions. (Back to top)

The engine shown on sheet #4 of the drawings has an engine block and a separate cylinder. Can these two parts be soldered together with soft solder, or must silver solder be used?

Normally you might be able to get away with soft solder. However, on this engine the steam motor is on top of the boiler and is, effectively, in the fire (the fire comes up around the sides of the boiler and there's still plenty of heat at the top). For this reason I'd strongly suggest that you use silver solder.

There are two main points to remember when silver soldering: cleanliness and heat. Make sure the parts are mechanically clean and properly fluxed with the correct flux. When heating the parts, make sure they are hot enough before applying the solder (usually a dull red heat for silver solder). And remember, solder flows toward the heat. Heat the parts from one side and apply the solder to the other for a good joint. (Back to top)

How does a person hold all the parts together to solder them up?

Are you talking about boiler parts? If so, a boiler is usually silver soldered in several heats. The ends should be soldered in first, one at a time. Then the top bushings, which will stay in place if they are on top while they are being soldered. To solder the bottom pieces that mount the boiler to the frame, I made a little fixture to which these pieces were screwed. This kept the pieces in line with each other and also the proper distance from each other. This assembly was then placed in position in the holes on the boiler bottom and soldered in. Then the fixture was removed and the boiler was ready to be installed.

Having said that, there is a lot to learn about making miniature boilers from copper (even simple, little ones), silver soldering (or silver brazing, as it is sometimes called), and testing. I suggest that you avail yourself of one of the excellent boiler-making books out there. (Back to top)

Any ideas on making the boiler ends...would think they should be rounded out?

No, they shouldn't be rounded out. For our engines, we flanged the ends around simple wooden forms (maple) turned in the lathe. Again, consult a book on boiler making regarding flanging. A flanged boiler end is a satisfying thing to make and it provides a very strong boiler.

For material for the ends, we used a piece of the same tubing that the boiler barrel is made of. First, split it lengthwise with a hacksaw. Then anneal it and fold it out flat. You can use a soft (plastic) hammer to flatten it on a piece of wood. Material this thick will not bow out under the working pressure of this engine. (Back to top)

Questions and answers
If you have questions about any aspect of Denver, send them to bannerworks@comcast.net. Within a couple of days, your question, along with its answer, will be posted on our Q&A page.




		Denver Q&A
*How much will it cost to build the Denver?* What kind of simple trottle and reversing valve do you suggest to upgrade this loco? What sort of grade is this loco capable of? *Can Denver* be built to 32mm gauge (0 gauge)? I've used 'silver-bearing' solder, but I've never used real silver solder. I know that my hardware-store propane torch will be inadequate by itself for heating the boiler parts, but would I be able to heat up the copper sufficiently for silver solder by using a tank of MAPP gas on the burner head? Do the drawings show an option for a double acting engine and a throttle? What types of reamers and taps are needed? How necessary is it to have a water glass and pressure gauge on small scale locomotives? The engine shown on sheet #4 of the drawings has an engine block and a separate cylinder. Can these two parts be soldered together with soft solder, or must silver solder be used? How does a person hold all the parts together to solder them up? Any ideas on making the boiler ends...would think they should be rounded out? How much will it cost to build the Denver? This is difficult to say. It depends a lot on what you already have by way of materials and machinery. If you have to buy a lathe before you can build it, it will cost a lot. However, if you are already tooled up and have a pretty good scrap bin, then it shouldn't cost too much at all. At a guess, if you have tools but have to buy all materials, gears, wheels, safety valve, etc., the cost will be perhaps $150 or so. (12-2-01) (Back to top) What kind of simple trottle and reversing valve do you suggest to upgrade this loco? Jim Reyer built a throttle for his engine. It is basically a needle valve mounted on a banjo fitting that attaches to the boiler at the rear where the steam line comes out. A reversing valve for the existing design would be much more difficult. To reverse an oscillating engine, you must exchange the steam admission with the exhaust. This is commonly done with a rotary valve (as on a Mamod), but our design did not include one for the sake of simplicity. If you used a fixed-cylinder engine with a valve, you could easily incorporate a slip eccentric into the design, but, again, our design did not include this. (12-2-01) (Back to top) What sort of grade is this loco capable of? Probably 2% - 3% with a light load. (Back to top) Can Denver be built to 32mm gauge (0 gauge)? I think it could be done. You'd need a narrower channel. The channel specified is square and I don't know if you could find a rectilinear channel of the proper dimensions. The alternative would be to cut the middle out of the larger channel and put it back together with a small plate at either end held on with some screws. You can cut the channel on the table saw if you have a carbide blade. It's nasty, but it works. You'd also have to remove the sprockets and chain between the axles from the inside of the channel. They could be moved to the outboard wheels, or you could just abandon them and have two-wheel drive. We haven't tried this, so don't know how it would work, but certainly the engine should power itself on just two wheels, and may pull a short train as well. (Back to top) I've used 'silver-bearing' solder, but I've never used real silver solder. I know that my hardware-store propane torch will be inadequate by itself for heating the boiler parts, but would I be able to heat up the copper sufficiently for silver solder by using a tank of MAPP gas on the burner head? You'll need to use real silver solder to do the boiler properly. I don't have any experience with MAPP gas, although I've heard that it burns pretty hot. I've also heard that you need a special torch head for MAPP cylinders -- you can't just use a propane torch. (Back to top) I use acetylene, with a tip about as big around as my index finger. Before that, I had a torch from Sears called "The Hot One". This is just a propane torch but somehow burns much hotter. It has a stainless-steel tip on it that gets red hot. It might be hot enough for a small boiler like this. Another alternative would be to get two or three friends, all with propane torches, to help you heat the boiler to red heat. You'll be astonished at how much heat is required to bring the copper to the proper temperature, but you must do it -- any less just will not work. (Back to top) Do the drawings show an option for a double acting engine and a throttle? No. As designed, the engine has no throttle and, to keep it as simple to construct as possible, we have only included drawings for single-acting engines (two different ones are included). However, both a throttle and a double-acting engine could be used, with a little ingenuity. (Back to top) What types of reamers and taps are needed? In checking a catalogue for industrial supplies for these tools, I discovered that there are straight shank, straight flute reamers; straight or spiral flute chucking reamers with a 45 degree lead chamfer; HHS drill length reamers with straight shank and straight flute; combination drill-reamers; chucking reamers with taper shanks; hand reamers; and, finally, taper pin reamers with 1/4" taper per foot. Which type is appropriate for the project? Likewise there are standard hand taps; spiral point hand taps; spiral point taps; combined tap and drills; fluteless taps; screw thread insert taps (STI); hand taps penta blue-style; spiral point taps-penta gray-style; Greenfield gun taps for through holes; Greenfield fluted taps for blind holes. Again, which is the correct style for the project? As is probably quite obvious by now, this is my first metal project of any kind, but I have to start somewhere. For reamers, you'll want a straight shank, straight-flute reamer. Most reamers I've seen have a chamfer to help them into the hole. Most low-cost reamers (all you'll need here) are made of HSS (high-speed steel). For taps, you'll want standard hand taps. Taps generally come in three varieties for any given thread -- taper, plug, and bottom. If they aren't specified, they're probably plug, which is fine. A taper tap tends to get into the hole a little easier. A bottom tap is for making a fully formed thread all the way to the bottom of the hole. A spiral-point tap is nice, but not necessary. With a regular tap, the tap must be backed off a little every half turn or so to break the chip. A spiral-point tap can be turned right in without backing off, as it pushes the chip ahead of it. This is fine for through holes, but with blind holes, you may end up with the entire chip stuck at the bottom (which may make no difference). A general rule of thumb, especially for beginners, is to buy cheaper, import tools. These tend to be general purpose, are made to reasonable tolerances, and will last a reasonable amount of time. You can always upgrade later when you are more experienced and know more. (Back to top) How necessary is it to have a water glass and pressure gauge on small scale locomotives? I've noticed many locos, including Denver, do not have them. Yet a friend, who models in larger scales, feels they are indespensable. On larger-scale locomotives, I would definitely agree with your friend. However, on small engines, especially simple ones, these amenities are not as important. The Denver, and other simple engines, run at relatively low pressure -- usually under 40 psi. Most pressure gauges, especially miniature ones, will not read accurately in those low ranges anyway. Also, the copper tubing out of which the boilers are made has a built-in safety factor of several hundred times, so even if pressure did rise above design specifications (which it won't if you have a good, working safety valve), the engine is still safe. A water glass, while useful, is also not necessary on small, simple engines. On an alcohol-fired locomotive, the biggest risk you run by running a boiler dry is damaging the paint. An alcohol fire is not anywhere near hot enough to damage a silver-soldered boiler. An engineer worth his salt will not let the boiler run dry anyway, because he'll keep a constant eye on the engine. When it stops, you blow out the fire. With practice, you learn how the engine behaves given various internal conditions. (Back to top) The engine shown on sheet #4 of the drawings has an engine block and a separate cylinder. Can these two parts be soldered together with soft solder, or must silver solder be used? Normally you might be able to get away with soft solder. However, on this engine the steam motor is on top of the boiler and is, effectively, in the fire (the fire comes up around the sides of the boiler and there's still plenty of heat at the top). For this reason I'd strongly suggest that you use silver solder. There are two main points to remember when silver soldering: cleanliness and heat. Make sure the parts are mechanically clean and properly fluxed with the correct flux. When heating the parts, make sure they are hot enough before applying the solder (usually a dull red heat for silver solder). And remember, solder flows toward the heat. Heat the parts from one side and apply the solder to the other for a good joint. (Back to top) How does a person hold all the parts together to solder them up? Are you talking about boiler parts? If so, a boiler is usually silver soldered in several heats. The ends should be soldered in first, one at a time. Then the top bushings, which will stay in place if they are on top while they are being soldered. To solder the bottom pieces that mount the boiler to the frame, I made a little fixture to which these pieces were screwed. This kept the pieces in line with each other and also the proper distance from each other. This assembly was then placed in position in the holes on the boiler bottom and soldered in. Then the fixture was removed and the boiler was ready to be installed. Having said that, there is a lot to learn about making miniature boilers from copper (even simple, little ones), silver soldering (or silver brazing, as it is sometimes called), and testing. I suggest that you avail yourself of one of the excellent boiler-making books out there. (Back to top) Any ideas on making the boiler ends...would think they should be rounded out? No, they shouldn't be rounded out. For our engines, we flanged the ends around simple wooden forms (maple) turned in the lathe. Again, consult a book on boiler making regarding flanging. A flanged boiler end is a satisfying thing to make and it provides a very strong boiler. For material for the ends, we used a piece of the same tubing that the boiler barrel is made of. First, split it lengthwise with a hacksaw. Then anneal it and fold it out flat. You can use a soft (plastic) hammer to flatten it on a piece of wood. Material this thick will not bow out under the working pressure of this engine. (Back to top) Questions and answers** If you have questions about any aspect of Denver, send them to bannerworks@comcast.net. Within a couple of days, your question, along with its answer, will be posted on our Q&A page. .
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