Critter Build
I've done some preliminary work on my critter for the NWSL & SML Critter Build. That translates to .. "I got to the point where I was confusing myself .. so I stopped"
I swiped the design off of a little Plymouth loco. in the photo below I have just sketched in the bearing blocks floating in the side-frame. That's where I stopped since the design of that bearing block directly affects how far out from the wheels those side-frames sit. My best guess is that the bearing blocks float vertically with a spring above them. Thought I would post this up for comments as for now .. I'm looking for a clue (I have few clues or brain cells). While sure .. I can come up with somehting .. and after all it's just a model .. but .. I am of the view that re-inventing the wheel makes little sense. If I can find a drawing showing how something similar works then all the better.
Found this excellent website with photos of Plymoth locomotives - Plymouth Part 1 .. and there are another five pages
This photo pretty much answers my question about the suspension too .
From the photo above this is what I think ..
F - This is the bearing. Pretty simple .. four large bolts hold the bering cap on.
G - The coil spring is compressed by the bearing block moving vertically between the guides E
E - These two vertical guides keept he bearing block moving vertically. Part E and part D are one part with a couple of bolts on D that fit into a slot in C.
C - these slotted pieces are pushed against D/E
B - Part of fixed side-frame
A - Adjustment bolts. These push C/D/E to retain the bearing block
You're right Ed. In that cast frame model the vertical spring is hidden in a pocket that bulges slightly on the inside of the frame. The bolted on bearing retainers underneath let everything fall out the bottom. Same as this fabricated version. The front axle is powered by a chain driven off a sprocket from the right side of the transmission and the rear axle a similar setup from the left side, ergo you'd have to drop the chains to get the axles and drivers out. Plymouth was evidently known for simple, rugged and easily maintained engines.
David, check this out. The frame is what looks to me like a large I-Beam with the spring pockets a cast assembly that bolts to the beam. Sweet. And .. it's narrow gauge.
Now that's cute! And it's a convertable! Not much spring travel there.This would be pretty easy to replicate and I love that log bunk in the background. A real start for a larger scale layout in small spaces.........
I worked on the design for my critter a bit this morning. My plan is to 3d print the parts and then make a mold and cast them in resin. Lessons learned .. I'm trying to make everything lock together via tabs etc. That way .. if successful (molds, castings etc.) it will be easy to epoxy everything together. it might be hard to see with all the colors but right now there are the two side-frames .. the green frame and the white extension bit will be one piece. They can be mirror images of each other so that's one mold. The - uhhh .. pilot/coupler pocket assembly (whatever it is called) will be one piece .. again I can get front and rear off the one casting. Finally the bearing block assemblies will be one casting also for all 4. That leaves the 'floor' that will connect the side-frames along with a mounting socket for the stanton drive. Once all that is figured out .. AND .. I can get a good .stl file to upload I will have the complete chassis. The superstructure .. shrug .. I'll scratch that out of styrene. That's the plan .. just thought I would post up the current state of the design for comment
If this works out Ed I'll take two of them. This is very,very cool.
Shawn Branstetter
shortlinemodelers.com
Ha. Well .. thanks. That gives me impetus to continue mission :)
I'm interested in getting recommendations for a nice little (10"x10") 3D printer for home shop use. Anybody have any experience with different brands? Thanks in advance!
Thanks for the info, that gives me a starting point. Nice work BTW!
Thanks Chris. There is a Japanese company supposed to be out with a desktop 3d printer in the 1K range. I've lost the link .. but there are starting to turn up. We are basically at the stage where the first DVD Recorders were .. from when the price dropped from expensive to cheap within a couple years.
Supposedly, this one will be available soon.
http://www.gizmag.com/3d-systems-cubify-printer/21091/
It looks like it might be a really neat little tool for the modelling community.
Yep. That's the one I was talking about.
Shawn .. might be interesting to peel the 3D stuff off of this thread and create another just for 3D
Hmmm. Ran across this article A Better Coupler for On30 Freight Cars on PacificCoastAirlinerr.com .. where he says "I have been looking for a better On30 coupler, a clunkier HO coupler. In Bruce Metclalf's dissertation on model couplers he mentioned the Accumate Standard coupler series as the right size. I assumed it would be Kadee, Mchenry size, too small with that "pencil neck geek look" skinny shank and that funky knuckle spring. I saw the Accumates on an HO Atlas car at a hobby shop. It was the biggest, klunky-iest HO coupler I had ever seen. The perfect On30 coupler."
Huh. That tells me that the #178 which is "a smaller head coupler which is more to scale" .. would be moving in the wrong direction then. Meh.
Think I will make that run to my LHS later ...
Shawn Branstetter
shortlinemodelers.com
Looks like if you just drill a hole (or cast it in place) for the center mounting screw ( in the coupler box)in the bottom piece (yellow) you could screw it up from the bottom into the blue piece which would secure the whole thing together. You'd have to tap the hole in the blue portion but that's not a big deal. The resin is easy to do. It would have to be a stepped hole. Clearance for the head part way through and then clearance for the shank the rest of the way. If that sounds too confusing I'll try drawing a picture.
The screw is a 2-56 self-tapping screw that came with the Kadee #205 Coupler Height Gauge.
I noticed that the instructions say - "secure with a #2 or 2-56 screw through the center hole or with two 0-48 or 0-80 screws through each of the two outer holes."
Sure. I could cut off the 2-56 screw .. but thinking that a couple of the smaller screws might work better.
I could also make the 'blue-bit' thicker .. it would just add weight (a good thing) for the little critter in 'real life' .. and I may end up doing that.
Again .. that's one of the things I like about using Sketchup is that I can virtually assemble the bits and pieces before actual construction .. and can catch some of the problems before that actually become .. a problem. :)
Yikes! I had no idea it was so thin. Does it really matter that the screw protrudes? Is there not something car body wise that will hide it? The radiator shell maybe? I'm always looking out for the easy way. Maybe you could find a screw that is shorter? There are suppliers that specialize. Believe it or not my local Ace Hardware store has a bin full of 2-56 screws of various lengths, in brass! Frankly, I'd just cut the thing off and be done with it after marking the protruding length and removing it from the assembly thereby saving the self tapping feature until the hole is complete. But I'm lazy and pragmatic and hate waiting for parts. And I love my Dremel tool.....
Ok. Smallparts.com has #0-80 Pan Head Phillips drive SS screws - qty. 100ea for $7.51
The problem with ordering things like this .. is that often the shipping is more then the cost of what you are ordering.
Total was $7.51 plus $5.02 shipping for a total of $12.53
That comes to 12.5 cents per screw .. which is exactly 1/4 the cost at ACE Hardware. I can live with that.
Hard to argue with any of the foregoing. I think the shipping cost is a little steep. I bet you could put them in a plain envelope and send them for 44cents. Or whatever the current rate. Now comes the waiting............Let's see, how can you use those 99 other screws Ed?
There are several ways around it of course.
- I could just cut off the excess is one.
- I like the idea of a pair of smaller screws though.
- Yeah. Like I said I could just raise the top part of the coupler pocket thingie
About the size. Yepper. It's hard to realize until you measure them but we are dealing with small parts here. That measurement of .273" for the current 'upper' part of the coupler pocket is 13 inches full size.
Like I've said though .. it's fun to play with the bits and pieces with them virtual .. makes it easy to try different things.
What I want is the two end pieces (upper coupler pocket) and side frames to epoxy to one piece. The coupler draft boxes would then fit into the recess and screw in. The lower bit of the coupler pocket would just be for looks.
The extra 98 or so screws? Well .. IF .. I were to sell a 'kit' .. I could include them. That's way ahead of where I am at the moment though since currently it's all 1's and 0's. :)
Like I said, hard to argue with the foregoing especially with visions of production dancing in your head. I'll take two, please. Nothing in the virtual world is any fun. I suspect Bill Gates has a rather extensive file of my "lost" data. To what end baffles me. Torture comes to mind though..........
Update: Pretty happy with the design so far. Ready to make .stl files now so that's good. Might do away with the 'bumps' over the springs. The yellow Plymouth at the top of this page has the springs showing .. that would probably be 'cool'. Still need to finsh the platform and however I need to secure the swivel pin. A U-shaped bit I think probably.
The only thing I see in this version is right at the lower front in the pic where the frame is made from some channel. That bit of channel measures .021" for the Flange Thickness and .060" for the Flange Width. My only concern is that this might be too weak when cast in resin .. think I will let it go and see how it comes out.
The steps on the U6's are .010" cast in resin. It is Micro Mark's high strength casting resin and they needed "tinkering" with but were useable if fragile. Shouldn't be too much problem at .021" I wouldn't think.
Yeah. Well .. I mean .. I am going to get it printed I think. It may require some tinkering with the model but that's fine too. I'm trying of course .. to make everything fit prior to that .. but .. shrug .. what it is .. is what it is .. and all that. I have some resin I bought from Smooth On .. a while back. Heck. Can only try .. and see what happens. :)
Good luck Ed, can't wait to see how it turns out!
This is pretty much it. That strap across the top that holds the stanton drive in is only about 1/8" .. might be too thin .. but then maby not. I can always replace it with a strip of brass later on.
I tossed on a quick and dirty superstructure. The strap and screws show but could easily be covered with a tool box in front of the cab there. The big thing is .. notice how the engine area is pretty much open. Could make for a nice little engine putt putting there. :)
A view from the back shows that the cab is also completly open. Kinda cool.
Yep, I think you've got it. Lot of creative stuff can be done above the chassis.
I think that's really the whole point of this exercise - that the Stanton drive being a powered truck allows a lot of freedom in that regard.
The next part is actually producing a good .stl file. That's difficult sometimes but .. fingers crossed. Will try tomorrow I think.
Okie Dokie. Last update for a while I suppose. I created a 'layout' of pieces to be printed. I duplicated the bearing block .. so I have one with bolt head and one without. Realisticaly .. I expect that they won't print that well on the one block .. but .. curious to see how well they do print. In any case .. here we go. This is an export from Sketchup.
.. and .. this is from the file I uploaded to Shapeways. it 'appears' to be ok .. but with 3D printing 'appears' is a close relation to 'assume'. To print this in FUD (Frosted Ultra Detail) will be $32.89 .. not cheap at all but .. shrug .. you gotta pay for the good stuff. I will probably place an order today after I FIRST pay my bills. :)
Shawn Branstetter
shortlinemodelers.com
Well .. yeah. I'm curious to see how it comes out. The bolts etc. yeah .. in fact I am printing the holes for the bolts. Doesn't matter if they are 'clean' as there should be enough to guide a small drill (although the FUD material is pretty good about reproducing such). First though .. bills .. always pay the bills first! :)
Edit: Placed the order. They said around 20 Feb. Guess I can start with the superstructure
You know how backward I am about computer stuff Ed, but I noticed that you have only one "sideframe" in the layout of pieces you uploaded to Shapeways. Did I miss something?
One sideframe .. and one end sill/coupler pocket also. I will use these .. add either styrene or brass bolts heads etc. and then use them as masters for RTV molds. That will let me cast them in resin. It was simply a cost thing since the sideframes will be mirror images of each other. I only had one coupler pocket assembly. Thing is .. I may want to re-work the design .. tweak it a bit .. so I was a little hesitant to just madly have pieces printed. I'm also cheap. :)
Interesting. I got an email this morning telling me of a UPS Ship Notification. I placed the order for the 3D parts on Feb 1 .. and got this shipping notification today. The email gives a delivery date of 09 Feb. Crazy. If true .. beats the heck out of 20 Feb. I suppose it could be a 'glitch' .. perhaps they are just getting the shipping label early. Shrug.
Prints came in. Here's what it looks like as it came in.
This is a VERY quick pic. They are still heavily coated with the support wax. I'll remove that tomorrow .. usually a good soak in alcohol works to dissolve the wax.
After I get the pieces clean tomorrow I will try to get some better photos.
A close-up of the bearing-cluster gives a good idea of the resolution of the print. I had one printed with NBW indicated by the red arrows. I wanted to see how well they printed. While they would be ok probably .. I'll use the other one without any NBW .. and use either styrene or brass NBW. That brings up two possible problems.
(1) The darn thing is so small .. just being able to attach the NBW in the right places ..
(2) This WILL require a two-part mold
Here's a close-up of the forward end of the side-frame with brass hex-head bolts (.5mm head). Just inserted .. not cemented yet. I figure some CAA from the bottom then clip off the extra length of shaft. They should work great and should reproduce nicely in a mold.
Incredible work Ed.
I'm getting ready to make a mold of the sideframe - using the 3d print as a master. I think I should say at this point that I am pretty much making this up as I go. I have made a couple of RTV molds (couple like two) so you need to take anything I am showing here with that in mind.
Here's the 'front' of the sideframe. I say 'front' .. meaning this is the bit that will be seen. I used "Simulated Hex Bolt 0.5mm Heads" from Scale Hardware. This is an excellent place for scale hardware (hence the name). The biggest problem I have is that the dang things are so small!
I had originally planned for a two part mold but .. I am going to try and get by without doing that. In the photo you can see the two rounded projections with the semi-circle cut out. These were for the springs and the plan was to use some small dia wire to replicate the springs. When I make the RTV mold, what you see will be on the bottom. The far side .. the 'bit' that won't be seen will be the flat open-face. One question I have is how to get that surface flat when I pour the resin. I *think* that at some point after I should either scrape the top of the pour .. or lay something flat across the open face of the mold after the pour. I found an article which states that this surface can be slightly concave or convex depending on the pour. Meh.
Here, I flipped the sideframe over so you can see the 'back'. The spring pockets are clearly visible here. I will attempt to make a mold 'as is'. If these pockets cause any problem I will simply fill them with clay and then continue with a second mold without any pockets.
In any case .. this surface will be glued down to a flat surface so the mold will pick up the detail from the other side.
The rubber will get into every cavity it comes across Ed, assuming you've removed all the air bubbles. I would suggest filling the spring columns with the clay or glue some styrene across the bottoms. Otherwise you are going to end up with some rubber sprues in there that are going to be very difficult to remove. I don't have too much difficulty making 2 part molds but do have problems casting acceptable parts from them. It's a real hassle getting the resin to flow smoothly all the way through and into the cavities. Goog luck. Looks really nice so far.
Got time to think about it. The 'Part A' of my RTV had set up dang it. Shelf life. Had to order some more.
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