Ignore this topic

[joe d]

Works for me. I'd never seen this one before, now that I have, I like it! (last time that happened, I married her :big

Joe

 

[GailInNM]

I have attacked a photo of the engine I built 20 years ago. I oiled it up and ran it on air last night. I was running it without a flywheel. It runs fine down to about 5 PSI and fairly well screams at 35 PSI. It does rattle and clank a little bit as the roller cam followers have too much end play in them, about 0.020. It should be about 0.005 so there is a little knocking. I will fix that before I put it away this time. I have never posted a video, so I really don't know how. I did check out my camera a few years ago to see if it really could make a video and it seemed to work OK, so maybe I can try it with a little hand holding from someone.
Gail in NM,USA

Edit: Couldn't polish then, can't polish now.

 

[bretk]

Gail,

I see you made the piston/rod as abuilt up assembly as opposed to one pc. I like that idea, 8) it seems like alot of brass to waste doing it the original elmer way. Is your engine sized per the dwg or scaled up?

-Bret

Vids are just as easy to upload via you tube, I reccomend 30 fpsand 320 image size settings on your camera, that will give a nice 10 sec video.

Let me know if you have any probs

 

[GailInNM]

Bret,
My engine is to print as far as sizes go.

Yes, I did build up the crankshaft/cylinder assembly. I can't remember right now for sure, but I think that I did three pieces. A 5/8 square brass for the cylinder, a 1/2 inch diameter brass for the valve, and a 3/16 diameter 12L14 shaft. Drilled and reamed the brass parts 3/16 and then fluxed everything and slid them on the well cleaned steel shaft and soft soldered them all together. I would have to pull it partway down to make sure. It's been 20+ years and I can't even remember what I had for breakfast any more.

While the built up assembly saves a lot of brass, it also saves a lot of time and reduces some of the more awkward turning of doing it Elmer's way. I made a few other changes which I will detail out for the group approval if we decide to go ahead with this engine for the team build, or will put in another thread if a different engine is chosen and "inquiring minds want to know." They are all minor and would not require any redrawing of any parts. There is also one change that I want to incorporate on my existing engine and would outline. Probably only about 15 minutes work to make the part from starting drawing to having the engine running again.

I created a YouTube account this afternoon and will play with video over the next day or so and if successful I will post here. Thanks for the offer for help Bret. But, I figure that if my grandson can do it, then I should be able to learn how in not more than ten times the time it took him.

By the way, for those of you looking for more details on the Comber engine on the internet, the actual name was Coomber. Notice the second "o" in the name. Still not a lot of information there.

Two links are:
http://cedesign.net/steam/coomber.htm
http://www.keveney.com/coomber.html

The second one is an animation of the engine so you can see how it works.

Gail in NM,USA

 

[bretk]

Gail,

I like the adjustable rollers on Cedges engine (your first link) maybe we need to think about a scale up of this engine?? ??? That is a mighty Bling Rich Rotary

-Bret

 

[GailInNM]

Bret,
There are lots of bling opportunities even if the engine is kept the same size and none of the operational dimensions are changed. I too like the adjustable rollers as shown on the first link (Cedges). To do them on Elemer's size engine would require that the cam ring be made larger to allow room for the adjustable portion and the piston rod also increased in length. One minor problem is that the piston rod would need to be threaded right hand on one end and left handed on the other so it would work like a turnbuckle. Otherwise your adjustment would be in 1/2 turn increments of the thread pitch used. Also, on Elmer's version, the roller forks guide the piston to keep the rollers centered on the ring, so the forks can not be rotated. This could be changed, but then there is the additional requirement to keep the cylinder centered on the cam ring. All this is possible, but each change means another place that error can creep into the build. If you make many functional changes, then you are starting over with a new design. I don't think that is a good idea for a team build. Certainly minor changes and bling should be a given however.

Bret, are you doing your version of Chuck's Horizontal in CAD so that it might be considered for a team build later. You are a little ahead of me in your version, but I am catching up - maybe. The more I build and look at it the more tinkering I think will be required to make it run well over a wide variety of input pressures. This might not make it a good team project. Still it is a fun project. I am documenting my changes in CAD, but only as working files and not finished drawings.

Gail in NM,USA

 

[Cedge]

Just for general information, My Coomber has a small flaw in the design. Apparently the builder miscalculated the main shaft support spacing by a small amount, causing a misalignment of the rotary valve where the shaft end play moves things away from it's proper seat. I've got it on my list of engines needing repair, but haven't gotten to it just yet.

Elmer's design also appears to be a bit more like the original Coomber design than mine.

Steve

 

[Powder keg]

I would like to see this double sized) I think it would make it look even better. Plus it would have more power. The adjustable rollers would be great also.

 

[bretk]

Bret, are you doing your version of Chuck's Horizontal in CAD so that it might be considered for a team build later. You are a little ahead of me in your version, but I am catching up - maybe. The more I build and look at it the more tinkering I think will be required to make it run well over a wide variety of input pressures. This might not make it a good team project. Still it is a fun project. I am documenting my changes in CAD, but only as working files and not finished drawings.

Gail,

I am keeping track of my changes, but not in cad, I am waiting for a licensed version of Autocad 14 from a friend who is changing cad software ;D but until then, I am back to the stone ages of pencil and paper. I ordered a 12 pack of springs in 2 different wire ga. for the internal exhaust valve from McMaster, so if you need some p.m. me your address and I will send you out some.

-Bret

 

[Bogstandard]

If I may, I will make a suggestion to all the people who want to make things bigger.

Just doubling up makes the build almost impossibly expensive. Just take the flywheel, rather than being 2" diameter, all of a sudden it becomes 4". Just price up the difference in cost of 2" and 4" material. I think you will find it isn't just double. Another example is the main ring, rather than being say 5" overall it becomes 10" and twice as thick. No only the cost issue raises it's head, whoever has to make them has to be able to hold such a size on their machinery.

It is easy to say double up, until you start to calculate how much it will cost you, not only in money but in resources.

John

 

[Powder keg]

Well, I have ten more done tonight. Sure goes slow? Maybe it just seams that way? So far that's 60 holes tapped.

Wes

 

[zeusrekning]

I am a "build it bigger" guy but John is right. Just for comparison a 2" dia 1" long piece of steel is .9lbs versus a 4" dia 2" long piece is 3.6lbs.
But all that said , I'm still up for a larger version.
Tim

 

[Powder keg]

I think I have enough bronze to donate for the flywheels. I'll look tonight) I'd rather have a bigger version also.

Wes

 

[GailInNM]

I am opposed to changing the scale of the build project. I think that the team build concept should be to build a known working design essentially as it was published. Minor changes are fine as long as one of criteria can be met.

First, the change will not affect the making of any other part so everything will fit even if all the other parts are made to print.

Second, the change can be made with universal agreement without changing the overall function of the parts or design. As an example, on the first team build the change was made to use 4-40 fasteners as they are far more common than the 3-48s shown on the print. even a change as simple as this requires that someone check the print to make sure that head sizes have enough clearance and there is enough "meat" around clearance and tapped holes.

This will give the best chance for success for everyone involved in the build project. If the overall scale is changed, then EVERY dimension on every part will change and introduce a risk for errors when all the parts come together for final assembly.

If a larger model is desired, I think that a different design should be selected that meets the criteria of size to begin with.

Perhaps in the future a second group, a team design group, could be formed within the team build section. There a design could be scaled, or even a new design generated. That design could then be considered for a team build project. I do think that at least one sample should be built to prove and refine a design before the design would considered for a team build.

Maybe we need to examine the philosophy of the team build concept a little bit further and maybe even define it more formally.

Gail in NM,USA

PS: I reserve the right to edit/revise the above after the second pot of coffee this morning.

 

[ksouers]

Well said, Gail. I'm in complete agreement.

I'm not comfortable at all with re-scaling a design, up or down. With so many parts to be made by different builders there are just too many opportunities for error. I suspect I would be the worst offender.

 

[Alphawolf45]

Initially I was under the impression that a team build would be of an engine that was larger and more complex than an average working guy would want to tackle in his own limited spare time..but Thats not right at all is it?.......But dont'cha think That engine is just too simple?
.

 

[kustomkb]

I was just playing with the coomber (thanks Gail) cam in CAD and got a distance across of 2.5425 and the given height of 2.625
does this sound about right?

 

[Powder keg]

I think this engine is simple enough that between ten guys Scaling it up won't be a problem. We can change the plans and have everyone redline them. I'm positive we can do it.

Wes

 

[zeusrekning]

Initially I was under the impression that a team build would be of an engine that was larger and more complex than an average working guy would want to tackle in his own limited spare time..but Thats not right at all is it?.......But dont'cha think That engine is just too simple?
.

Smaller to me is more complex. My prefrance is the medium sized engine. I would like this one in a larger version. I think it is a unique design. I should be able to scale it up in solidworks if no one else wants to do it. But I am also fine with doing it as is if that is the decided way. I was not very impressed with the Elmers Open Column enigne idea originally but as the build progressed and as I started recieving parts I really started to have a new opinion of it.
Tim

 

[Brass_Machine]

...
Perhaps in the future a second group, a team design group, could be formed within the team build section. There a design could be scaled, or even a new design generated. That design could then be considered for a team build project. I do think that at least one sample should be built to prove and refine a design before the design would considered for a team build.

Maybe we need to examine the philosophy of the team build concept a little bit further and maybe even define it more formally.

...

Gail,

That idea has been in the works for me since I have had the idea for the team builds. Team Design is next on the plate for me (With Rick's approval). That is something I want to see happen as well. I mentioned the idea a long time ago. I want to see the team build idea work out all of the kinks first. Then get the team design moving along.

I would like to see the team design do things from upscaling builds to designing from scratch builds.

The philosophy of the team build was originally my idea. I wanted people to get involved with one another that goes beyond the board. I wanted people who are new to machining to be able to jump in and learn. I figured it was a good way for newbs and masters to work together and learn new things. Nothing improves your work like making the same piece 10 times in a row.

My opinion is this. The team build works on proven builds with only minor modifications (like the Elmer's OC). We allow for artistic creativity (with the team's approval).

Once the team is comfortable we can move on to larger projects. The smaller engines as well helps control the costs involved.

If anyone has different opinions... lets hear them.

Eric