Model Railroad Parts

[johntech]

This is a test piece in MDF of the end piece for my model railroad rotary coal dumper. The final cut will be in 1/4" gray PVC. I used DraftSight (free) to do all my cad work.

Also included is the mid support bracket that will go between the 2 end pieces

[JimG]

This is a test piece in MDF of the end piece for my model railroad rotary coal dumper. The final cut will be in 1/4" gray PVC. I used DraftSight (free) to do all my cad work.

Also included is the mid support bracket that will go between the 2 end pieces

John,

That's looking good. I notice you haven't cut any gear teeth on the circumference.

Jim.

[johntech]

This is a test piece in MDF of the end piece for my model railroad rotary coal dumper. The final cut will be in 1/4" gray PVC. I used DraftSight (free) to do all my cad work.

Also included is the mid support bracket that will go between the 2 end pieces

John,

That's looking good. I notice you haven't cut any gear teeth on the circumference.

Jim.

Thanks Jim

So far I'm just trying to get the front side correct for and the milling speeds and depth per pass right. I don't know how or what size teeth to cut in there. I also have to figure out how to flip this over, using DraftSight and Cut2D, because I have some things on the back side I need to mill so the support pieces all fit together in alignment. Right now with the track in there the knuckle on the coupler will be right at the center of rotation.

If you have any ideas on making the gear teeth around the circumference I would be greatful for any information you could pass along!
Thank you
John

[dhellew2]

Draw one tooth then use a array to do the rest.
The easiest way to do two sides is to use alignment pins located at the y-axis center line of the part. To make life easy locate the pins using the CNC with the first pin at an even dimension from x-zero y-zero, then along the x-axis at the same y-axis as the first pin. I use snug fitting dowels for pins, just lift the part up and turn it over. Hope this makes sense and helps. Dale

[JimG]

So far I'm just trying to get the front side correct for and the milling speeds and depth per pass right. I don't know how or what size teeth to cut in there. I also have to figure out how to flip this over, using DraftSight and Cut2D, because I have some things on the back side I need to mill so the support pieces all fit together in alignment. Right now with the track in there the knuckle on the coupler will be right at the center of rotation.

If you have any ideas on making the gear teeth around the circumference I would be greatful for any information you could pass along!

"dhellew2" has covered both points and I can add a bit to what he has suggested.

On machining two sides, you might want to download the tutorials for Cut3D. Cut3D can machine on two or four sides and there is a section of its manual dedicated to how to deal with holding and locating the workpiece. If you are not happy at flipping work parts accurately, you might consider cutting two half depth sides and glue them together after cutting. Do the two sides in one CAD file using "MIRROR" to copy details from one side to the other, then cut both sides at the same time with the same settings.

If you only want representational gear teeth, then what "dhellew2" suggests will do fine. But if you want to actually use the gear teeth to operate the model then you might want proper tooth forms and you might want to look at a program like Gearotic to do that

http://www.gearotic.com/

....or maybe this is getting in a bit too deep.

Jim.

[johntech]

Draw one tooth then use a array to do the rest.
The easiest way to do two sides is to use alignment pins located at the y-axis center line of the part. To make life easy locate the pins using the CNC with the first pin at an even dimension from x-zero y-zero, then along the x-axis at the same y-axis as the first pin. I use snug fitting dowels for pins, just lift the part up and turn it over. Hope this makes sense and helps. Dale

Hi Dale

OK I guess I hadn't considered that idea! The piece I will cut this out of is 9"x9" so I could put 2 alignment pins in the center section that will eventually be removed. I have put "Tabs" all through the piece to hold it all together until done milling then just flip it and mill the other side. Good deal

Thank you

John

[johntech]

[
"dhellew2" has covered both points and I can add a bit to what he has suggested.

On machining two sides, you might want to download the tutorials for Cut3D. Cut3D can machine on two or four sides and there is a section of its manual dedicated to how to deal with holding and locating the workpiece. If you are not happy at flipping work parts accurately, you might consider cutting two half depth sides and glue them together after cutting. Do the two sides in one CAD file using "MIRROR" to copy details from one side to the other, then cut both sides at the same time with the same settings.

If you only want representational gear teeth, then what "dhellew2" suggests will do fine. But if you want to actually use the gear teeth to operate the model then you might want proper tooth forms and you might want to look at a program like Gearotic to do that

http://www.gearotic.com/

....or maybe this is getting in a bit too deep.

Jim.

Hi Jim
I will check out the documentation as you suggested. As far as the teeth around the outside, I may look into that program. When I clicked on the link above I got a message saying the site didn't exist. If I do a google search there is a ton of listings for it. He must not have a HOME page as I did find the page to download the file.
If the tooth idea doesn't work out I had originally planned to mill out a "pulley" on the back side and use a belt drive to turn it.. We'll see which one works out. Either way I'll keep you all posted on here on my progress!

P.S. Is there any way to keep this editor window from scrolling off the line you are typing on?? I't such a pain to see what I have typed as it constantly scrolls back to the top of the message.

Thanks for all your suggestions

John

[johntech]

I finally got my first 2 sided end piece cut for my Rotary Dumper. I ended up using the pins used for shelving support out of one of my old "sawdust" made cabinets. Worked out very nice.
I had planned trying to make the gears around the edge but opted for a flat belt drive.

John