Member postings for Model Enginerd

Awesome. Thanks for the tips. I'm still pretty new with Alibre.

This was an interesting study. I tried an approach using expressions so the user could pick the TPI and diameter and the geometry would auto gen. I had 16 TPI in this one, which is pretty tight. Another design consideration was the outside diameter measured from the outboard cutting edges didn't necessarily match the pitch, so the pitch was adjusted slightly to meet the O.D.

Another thing is that I don't know how Alibre handles arc lengths. It doesn't do radians. I did manage to create geometry but was unsuccessful in automating all of the inputs.

In retrospect, as someone else mentioned, it would be better to force the TPI and the diameter together, so when the steel is rolled and welded, the teeth will be offset at the weld.

Synchronous modes are typically a last resort tool for dumb solids but can be handy when you are working with a lot of people and want some sort of history in the design tree.

You can change a hole diameter in a sketch, or you can add a synchro at the end of the design tree and name it to your current rev.

As for migration from any CAD package, it is a good idea to call it a loss and export everything into STEP/IGES. I just eat crow and resketch models if necessary.

I only buy modeling tools I can own for this reason, even if they might be subpar. Alibre, Rhino and Zbrush are still good tools I only have to buy once. Hopefully I don't wake up one morning to find out they snuck a kill switch like Fusion 360 did!

Really nice. I'd like to make some wheels like that on my rotary table.

Condensers are placed in parallel to commutator segments to dampen spikes that both generate EMI or could damage a controller upstream. I was taught in similar applications that if they go out, you might also get premature wear out of your carbon brushes, but some would differ on it. Looks like the brushes are gone and you were down to the metal, which might be why it's not running correctly.

I'd try getting a new motor like they suggested, or you could turn down that commutator and get some new brushes installed. I've installed brake pads on bad rotors and had them break in ok. hehe

@Pero Interesting on the solder. I've always done welding and brazing but new to silver solder. I bought extra to practice on.

@br Nice. I'll have to look more for the videos. Probably need to work more on my Google-Fu.

Hi Pero,

Yeah, it seems the solder is mostly there for the fittings and to seal the riveted gaps non-structurally. I thought about trying different grades of silver (cooler/lower % throughout the build), but for now I'll stick with the print.

I'll need all the luck I can get!

Hello all,

I'll be posting a build diary of PM Research's #1 Boiler build. This will hopefully be used to power a steam donkey as part of my garden railroad project (G scale).

I have plenty of experience with aircraft pressure vessels, repairs, and the importance of properly executed engineering data. Nonetheless.....

....grouchy boiler of doom comments are welcome for part of my/our educational edification.

Here's an unboxing video I just did of the boiler kit in case anyone's interested on what tools one might expect to build one. I was surprised to find that one could get away with more basic tools (and a small lathe). The bigger mini lathes would eat the project for lunch.

As a side note, I've also started machining the skidder's gear train, which will be setup like this (rotate CCW 90° ) .

Here's one of the gears and pinion already cut with home brewed cutters...

Now that I have a boiler with dimensions, I'll be able to move forward with the tricky part of tying geometry together and getting things to (sort of) look to scale.

Anyways, the boiler itself will keep me busy for a long while. I'll be running some of my other little engines on it, which have yet to run on steam.

Regards,

-Z

*Helpful References:

• PMR Drawings
• Boilers: Types and Design (ICS)
• The Steam Donkey Engine (Harris)
• In Search of Steam Donkeys (Johnson)
• Mechanics of Materials (Beer, J)
• Practical Stress Analysis (Flabel)

Edited By Zeb Flux on 14/05/2021 22:18:42

I've seen some guys go to the extreme of calculating the lens that was used in an image, undistort it (in programs like Blender) and dial in the guesswork.

Photogrametry/scanning can be used as well if the original is available and you have the ability to scan around it. Some impressive models are coming out from new phones with lidar. These points can be placed to scale in 3D space for reference. That said, I think most of the time spent is researching accurate references. Nothing beats accurate orthogonal views. Pureref is a great program for organizing references.

Below is an example of a steam donkey I'm working on. I used the technique discussed by others using orthogonal views to generate geometry.

I'm using geargenerator.com to generate the gearing I want, which is constrained to the tooling I have available. Here's an example (You can save your file as the URL, which is pretty cool). I can drop an image of it to scale in this model.

Once I drop that in, I can parametrically adjust the steam yarder's geometry to accept the custom gear train and boiler. Dummy models of the pitch diameters are good enough as the critical data is saved in the gear maker.

Here's another side project of the Daylight GS-4 I'd like to build some day in live steam. In addition to the main views, section views are also set in 3D space.

Not sure if that's helpful but interested to see how your project is moving.

-Z

Knipex for the win! They are great for aircraft use, both for turning fasteners and squeezing smaller rivets.

When I was on my moldmaking apprenticeship, my lead was showing me the ropes. The first lesson was his left hand, which had three fingers busted over from being in a hurry and trying to slow a large spindle. I don't think it was a guard that would have saved that, more the idea that you have to take your time and think where you're putting your body. If a guard helps towards that end then it's a win.

Scariest things, even on the little lathes, are a file (without a handle) getting jammed in the top side of the chuck or like someone said, those long purpley-blue strands of steel chips that will get around your ear.

Always nice to be machining in a t-shirt on a smaller lathe with magnification, and the tiny part is in a collet. Happiness.

What materials are you turning?

Some thoughts come to mind:

• The least preload possible to obtain the desired outcome. Larger Øs and heavier cuts (work deflecting) will require more preload.
• Some type of grease (moly/bearing) to interface contact surfaces.
• Slowest speeds possible (reduce heat/friction).

I now venture to hurl myself at the mercy of forum experts with this adventurous project. Hopefully I got the embedded video correct.

Edited By Zeb Flux on 17/04/2021 04:30:38

Edited By Zeb Flux on 17/04/2021 04:33:18

Very nice!

Hello all,

I'm an aircraft guy but have been enjoying tinkering with more manageable old guy hobbies (I'm not that old).

I spent several years restoring and maintaining aircraft/rotorcraft, working as a toolmaker (below), and drafting.

Just joined a garden railroad club...Good stuff. Currently cutting gears for a very miniature steam donkey (yarder) and drafting up a model.

Regards,

Zeb

I was unaware of that. Sometimes I can pick up on new tools scrolling through suggestions.

I'm kind of on the other path. I picked up "Principles of Engineering Graphics" to learn how it was done the old school way. I have the big pile of Spitfire drawings and am always amazed at how quickly they got stuff done, even with the stack-up errors and such.

I found that after learning one software, the rest follow a similar path.

I stand corrected.

I re-read the post, and I guess I see the emphasis being towards the Chinese stuff. I know for certain the runout is much higher and the plastic gears on a lot of them wear out prematurely and are noisier.

Making smaller parts usually means tighter tolerances. If the work wobbles, you could get away with turning work close enough. You would be far less likely to successfully do the same cutting without chatter by hand (Cris/Clickspring style). If it were me turning small diameters under magnification, I'd buy a high quality headstock ($107.25) and leather band it to my antique treadle.

Do the Chinese lathes have provisions for W-W collets?

The Sherline set is very accurate and rigid for its size. Highly recommend the mill with the adjustable angle plate and rotary table. The best part is I can grab either and set them on the kitchen island and go to town.

As long as one is patient making light cuts it works great on larger items. There's a good article of a gentleman turning an Ø8 1/2" flywheel on the mill. The reason I mention the mill, is that I can turn reasonably sized items on the lathe, then move the chuck+part directly on the zeroed mill and back with no issue. The chucks can mount on the rotary table, the mill spindle, and lathe tailstock too. If Z clearance is an issue, they make an extension and/or a horizontal milling setup using the same machine.

Downside is the machines can get corroded quickly. If you're an oddball like me and like cleaning after use, I clean, grease all contact surfaces, and WD40 the rest with a paper towel. If you don't have a heated garage, they can be set in a cabinet or closet during the winter. Because of the light cuts and cheap HSS, I hardly use coolant, so a vacuum zips up the swarf in quick fashion.

Agreed. As a full-time drafter running the fancy stuff during the day, Blender is not necessarily CAD friendly, but it can be forced to do the job. I've been using it for almost 20 years, and I still feel behind on the features.