Author Topic: ELMERS NO.7 square (Read 3883 times)

Jon Cameron · « **on:** February 12, 2018, 10:37:46 PM »

Hello guys,
About to embark on building the no.7 square, just wondering if anyone has any tips on making one.

I found this useful write up on here and have read through,
http://www.modelenginemaker.com/index.php/topic,5605.msg107989.html#msg107989
Anyone any other useful tips?

AOG · « **Reply #1 on:** February 12, 2018, 11:01:08 PM »

The thing to remember is that the extruded square has a fairly uneven inside surface. I ended up wrapping my cylinder in Teflon tape to get it to seal properly on the sides. Otherwise it’s a relatively easy build.

Tony

Jon Cameron · « **Reply #2 on:** February 12, 2018, 11:12:04 PM »

Hi Tony,

Firstly thanks for the great write up, I won't be able to do anything as good as that on here, just a few pics as I progress?? along.
Secondly I've been thinking about the extruded length and I think a lap could be made (a chew to do it though) to lap the inside of the square extrusion. It doesn't necessarily have to be square, so long as the opposite sides are parralel. A lap could make it slightly rectangle but would smooth it out hopefully. Time will tell.

bouch · « **Reply #3 on:** February 13, 2018, 06:02:03 PM »

Quote from: Jon Cameron on February 12, 2018, 11:12:04 PM

Hi Tony,

Firstly thanks for the great write up, I won't be able to do anything as good as that on here, just a few pics as I progress?? along.
Secondly I've been thinking about the extruded length and I think a lap could be made (a chew to do it though) to lap the inside of the square extrusion. It doesn't necessarily have to be square, so long as the opposite sides are parralel. A lap could make it slightly rectangle but would smooth it out hopefully. Time will tell.

I must have been lucky, as the tube I got was pretty good. I made my piston oversize by a few thou, and then slowly filed/sanded the edges until it was a nice sliding fit. No packing necessary, but took a while to get the piston to fit well in the tube.

I used silver solder to attach the end onto the cylinder tube. But be careful here. I made a fixture out of aluminum to hold the end in place, the AL slid into the tube so I could solder from the outside. But the aluminum expanded at a faster rate than the brass tube, so it bent the tube sides out and generally made a mess of things. Needed to scrap that one and do it over with a smaller fixture to prevent that.

I used a "silver bearing" solder to attach the tube to the body, higher temp than 60-40, but lower temp that true silver solder, so I wouldn't melt the end of the cylinder off.

Here's a video of mine running:

<a href="https://www.youtube.com/watch?v=ieEJ3_R2ui4" target="_blank">http://www.youtube.com/watch?v=ieEJ3_R2ui4</a>

Later, I made a display with 3 other Verburg engines, so you can see it running again here:

<a href="https://www.youtube.com/watch?v=64ryrzKvuYw" target="_blank">http://www.youtube.com/watch?v=64ryrzKvuYw</a>

Now I have to make yet another display, as I've found I still need to make #19 "Standby" to finish the "family"

(and don't they look nice made out of all brass?

)

Jon Cameron · « **Reply #4 on:** February 13, 2018, 07:45:49 PM »

Hi Bouch,
I saw your video on line, of the family 😀
Very nice all lined up on an angle like that.

I guess see what the square piece is like. I had hoped to use a 3/8" piece of brass for the piston, but it won't work as it slides through the square cylinder with a fair bit of wobble room. So will have to turn down a slightly larger piece instead.

Jon Cameron · « **Reply #5 on:** February 15, 2018, 01:42:32 AM »

Question for you all, is 0.003" too much play in the piston to cylinder fit?
I measured the tube tonight afterfacing off to length, the internal dia is 3thou larger than the 3/8" unmachined piece of brass I had in mind to use. By the time it's machined I imagine it will increase to 5thou min. Should I just find a larger dia piece of brass to machine down? To me 5thou is too much.

The internal of the square extrusion was checked in several places and found to measure the same both ends and across the square. So at least that's a result.

b.lindsey · « **Reply #6 on:** February 15, 2018, 02:02:07 AM »

Not having made this engine, I can only speculate. .005" is a lot I would think. .002" sounds better. It might run with 005" clearance but will take more air due to the blow by. Maybe bouch can measure the clearance on his.

Bill

toolznthings · « **Reply #7 on:** February 18, 2018, 02:34:59 AM »

Was looking at that engine, too. Having the cylinder as square as possible would be the best. Probably the hardest part to make.
Will watch your build.

Flyboy Jim · « **Reply #8 on:** February 18, 2018, 03:16:25 AM »

I hope you do a build thread Jon. They are really fun to do and, as your finding out looking at Tony's build thread, really useful to future builders.

Jim

Jon Cameron · « **Reply #9 on:** February 18, 2018, 08:54:28 AM »

I've done a few build threads, the problem is remembering to take pics lol.

I did make a start on the base and frame and cylinder, facing everything to length. Went too far with the base and it's now 0.002" underside but since this isn't a size critical part then I think I'll get away with it, but need to make a wiggle pin next to align the holes for drilling.

I'll post some pics after I've taken them at some point today.

Jon Cameron · « **Reply #10 on:** February 18, 2018, 08:57:53 AM »

Quote from: toolznthings on February 18, 2018, 02:34:59 AM

Was looking at that engine, too. Having the cylinder as square as possible would be the best. Probably the hardest part to make.
Will watch your build.

I measured the internal dimensions at both ends of the cylinder, it seems to all match so I feel trying to do anything internally to polish the bore would only cause more problems down the line.

Jon Cameron · « **Reply #11 on:** February 19, 2018, 11:44:17 PM »

Well I made a start on the engine tonight. Starting with what I knew was going to be a pain. The long thin hole for the steam feed. What do you know a dead centre doubles up as a wobbler stick to dial the hole in.

The long thin hole didn't go according to plan which means I'll have to take account of that when I build the crankshaft and bearing. Also it appears my chuck wasn't done.up tight when I drilled the long hole which accounts for the wobbly hole, seems I missed a jaw on final checks.

The cylinder base and frame all sized to length and cleaned up

Edit give me some time to work out how to post pics........

Jon Cameron · « **Reply #12 on:** February 20, 2018, 12:07:37 AM »

Hope this works

crueby · « **Reply #13 on:** February 20, 2018, 12:17:45 AM »

Photos are showing up fine!

Jon Cameron · « **Reply #14 on:** February 20, 2018, 12:30:15 AM »

Thanks for confirmation, I'm on my phone, so had to send the photos via messenger to get them to reduce in size to load. I feel sorry for my friend that's received four photos with no idea why lol

b.lindsey · « **Reply #15 on:** February 20, 2018, 12:31:27 AM »

Jon, the pics are fine but if you can resize them smaller even better. As I recall Jo was going to reduce the maximum file size to 512kb per pic. Thought she had already. The long hole doesn't look too bad. Should be able to compensate for it without too much extra effort.

Bill

Jon Cameron · « **Reply #16 on:** February 20, 2018, 02:24:40 PM »

Hi Bill,

I don't think I can reduce the pics much more without been on a computer.

The hole is only slightly off and I can compensate for that by just filing the slot slightly longer in the crank shaft so not a big worry
Ill try get some more done today 😊

Jon Cameron · « **Reply #17 on:** February 20, 2018, 06:38:57 PM »

A little more done today, turned the bearing, and faced off both sides, and tried it in the engine frame and also tried the crank inside it. All seems well.
https://flic.kr/p/23ataog
https://flic.kr/p/24wHVYx
https://flic.kr/p/24sJ3cj

bouch · « **Reply #18 on:** February 22, 2018, 06:06:24 PM »

Hi Jon,

I'm trying to figure out what you're doing (or maybe Why is the right question) in the 2nd photo there.

Are you simply test fitting the part in the lathe into the body? Or is the body spinning around when you're doing the machining? (hoping the former...)

Jon Cameron · « **Reply #19 on:** February 24, 2018, 03:13:28 PM »

Yes Bouch it was just a test to make sure it fit as the last two attempts had been a little wobbly so they were scrapped.

The lathe wasn't set running in the configuration shown in pic2.

News:

Author Topic: ELMERS NO.7 square (Read 3883 times)

toolznthings