Chapman GP7 Project

Re: Chapman Chassis Project

Postby Tom Dempsey » Sat May 28, 2016 12:42 pm

As long as we can get more average lifespan than a first generation LifeLike N Scale GP-38!
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Re: Chapman GP7 Project

Postby ConnRiver » Fri Jul 01, 2016 1:09 pm

Changed the thread name from . . . "Chassis" . . . to "GP7". . . .

I've got 2D and 3D drawings to submit here, hoping to draw comments (like, 'yeah, you're on target,' or, 'I think you made a mistake there').

My intention was to create the power chassis first, but, as usual for me, I changed up. I thought that by creating the walkway (with pilots and steps), the chassis/frame could be easier designed to fit that. A best approach.

But, then, I changed my mind once again. If I drew a GP7 PhI in 1:1 scale in its entirety, I could then pull out sections, such as the walkway, piece by piece and construct those pieces in 3D and fit all together. With the 2D and 3D versions finished, it'll be on to re-scaling in TT and then preparing parts to be CNC cut.

That's my plan, and I'm sticking to it . . . until I change my mind again (and, if I do, please shoot me).

Brian C. / Cedar Rapids, Iowa
Last edited by ConnRiver on Sat Jul 02, 2016 12:34 pm, edited 1 time in total.
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GP7 - The 1:1 Drawings

Postby ConnRiver » Fri Jul 01, 2016 1:51 pm

My primary source for creating this locomotive in 2D was the GP7 Ph I locomotive drawings found inthe October 1982 Mainline Modeler.

Ever cautious, though, I cross-checked with a number of other sources, including GP7 photos found online, photos and measurements I made of CNW GP7 units stored at Oelwein, Iowa, and Scott Chatfield's essays on the GP7 and its phases. The dozens of close-up photos and measurements of a GP9 made by a fellow on the Diesel List was more than helpful.

I've made numerous adjustments to this set of drawings as information is cross-checked. And will continue to do so throughout the process.

At times, the line drawings will include 2-degree angles in hidden areas. These represent draft faces that will aid in de-molding when the time comes.

The red lines on the side views represent the location of the chassis frame as they do on the cross-sections found on the far left. The top cross-section drawing, from Mainline Modeler, confuses me. The chassis falls two feet from the top, far deeper than is visible in photos or within drawings. The bottom cross-section drawing is the first iteration of the chassis/frame I created for the model. -Brian C.

1 - GP7 ph I dwgs.jpg


2 - GP7 ph I dwgs.jpg
Last edited by ConnRiver on Sat Jul 02, 2016 12:34 pm, edited 1 time in total.
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Re: Chapman GP7 Project

Postby Bernd » Fri Jul 01, 2016 8:26 pm

Drawings look good Brian.

From all that you've said I don't think there is much to point to as being wrong. I've heard complaints from HO scale modelers of door sizes being off and that the doors are supposed to be flush with the hood. It's hard to tell from your drawings about any minor details because of the small size of the drawings.

I'm not one to complain if a dimension is off on a model. If it looks like a GP7 then I'm a happy camper.

Keep up the great work. You're doing better than me.

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Re: Chapman GP7 Project

Postby ConnRiver » Fri Jul 01, 2016 9:09 pm

Bernd, hey,

I'm not yet used to converting AutoCAD drawings, thru Photoshop, into JPG files and sizing them usefully. Hope to get better at it. If anyone here wants them larger, I'll try to achieve that.

The doors are flush and heights match those Scott Chatfield writes about in his comprehensive paper about the various phases.

Doing better than you? Thanks, but I don't think so. I've not produced one item yet. . . . And this one will take awhile. (Oh, maybe you mean drawing up a loco?) Tedious going, but I'll finish at least one powered model to see if it's acceptable by the TT community.

-Brian C.
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GP7 - The Pilot (3D)

Postby ConnRiver » Sat Jul 02, 2016 12:31 pm

Here's my first GP7 Ph I 3D piece (I tossed all my previous 3D work). The pilot is created in four pieces: 1 - The main (large) plate; 2 - The bottom (small) section with the steps; 3 - The coupler buffer; 4 - Steps.

The main plate and bottom section are separate so that various styles of bottom sections can be accommodated. Boy, the steps are going to be a pain, though - they're so small. I have drawn them with locator tabs to fit into slots on the bottom section. Have to see how they come out.

Please remember how small these pieces are and how large they appear on screen. I have not contoured the rivet/bolt heads since they can only be inspected on the model by magnification. If objections are made about their shapes, I'll attempt to shape them when cutting. On the HO P2K GP7 model the bolt heads are no more than tiny buds nearly invisible.

On the rear of the pilot I've attempted to add strength by thickening areas that won't be visible from trackside.

Any thoughts?

Next Up: The 3D walkway with pilots.

-Brian C. / Cedar Rapids, Iowa

3 - GP7 ph I - Pilot-front.jpg


4 - GP7 ph I - Pilot-rear.jpg
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Re: Chapman GP7 Project

Postby Bernd » Sat Jul 02, 2016 5:34 pm

ConnRiver wrote:Doing better than you? Thanks, but I don't think so. I've not produced one item yet. . . . And this one will take awhile. (Oh, maybe you mean drawing up a loco?) Tedious going, but I'll finish at least one powered model to see if it's acceptable by the TT community.

-Brian C.


Well you're doing better with the 3d drawing than I. I've tried some 3d modeling and just have a hard time. 2D cad drawings no problem. I just can't get the programs to work like I want them to. I do better with an actual part.

Keep up the good work. I'll definitely get one once you get into production.

Keep up the great work.

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Re: Chapman GP7 Project

Postby ctxmf74 » Sun Jul 03, 2016 1:25 am

"Any thoughts? "

What material and method do you plan to build this body from? I think optimizing the design for the production method is more important than the smallest details. TT engines are so small that most of the tiny stuff can't be seen so I'd design it for reliability in use,ease of coupler installation, ease of parts creation and assembly, and cost of production when choices need to be made. I think the detail level and construction of the MTB Sazmodel switchers would be a good target. They came in a reasonable price and run well. The only things I don't like on them are the frame material is hard to drill for handrails and the coupler mounts are too complicated due to their need to use Euro style couplers along with US style, but if MTB built some different types of US engines with the same design style and quality I'd be happy to buy them .....DaveB
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Re: Chapman GP7 Project

Postby ConnRiver » Sun Jul 03, 2016 10:59 am

Dave,

I can't stress this enough: I WANT your help, and the help of others here who wish to pitch in. I have limited knowledge about railroad models, this is where your insights will be vital. HELP me choose the best practices. It's why I'm uploading my first project here. Couplers? Guide me along to creating the best possible application. What coupler(s) should I buy now to have on hand with which to experiment? What sort of attachment to the frame do you want to see for the coupler box?

I'm guessing the casting masters will be CNC cut from Ren460 and machinable wax - those materials cut like butter. Casting? It's been years since I've pressure cast. This time around I will pressure cast and cure under pressure and HEAT, which I've read is capable of producing results rivaling that of injection molding and virtually without shrinkage. We'll see. Resin? I'll have to research, new resins are appearing all the time. I'll check with the knowledgeable fellows at the Casting list.

I have a used vulcanizer and a new spin-casting machine . . . that I've never used. A learning curve there, but I hope metal frames can be produced with it. Metal type? Unknown at this point. Research. . . . But we want drillable metal, right? (Thanks for mentioning that.)

I have experience creating double-sided etching artwork, so I'm comfortable if that process is called upon. I'd like to discover what company Plano uses to produce its etchings since that company will be experienced working with model railroad items.

Details? I've got an SLP DLP 3D printer here 90 percent assembled. Yet to be determined what it will be capable of creating. I'll finish assembling when the time comes its use is needed.

N/S wheels. A fellow on the Sherline (CNC machines) list developed an automated cutting routine with which he cuts model railroad wheels. I've got the software and hardware to replicate his process. (At YouTube there is a video of his machine at work.)

Later today I hope the 3D walkway, including pilots, will be ready to upload here. It's modeled after the P2K GP7 HO model with clip-to-frame long hood, short hood, and cab-base. Is this what friends here want to see? Is there a better method to assemble shell to walkway/frame? PLEASE let me know.

This project will be a lengthy process for me. It's all about learning. Once I've got good, solid techniques under my belt, I might be able to "zoom" along with following projects. I do have an F-unit B CAD drawn. . . . And steam, I've got most of Gordon Odegard's 2-8-2 (MR 1982-'83) CAD drawn as well. (I've collected the essential British books about steam locomotive modeling.) Is there interest here in steamers?

Motors, believe I'll buy a couple or three Mashima 1024s to have on hand for when it's time to work on the drive train (and that's next up). Anyone here have extra 1024s you are willing to sell? Down the road I intend to search for a supplier who will wholesale motors (after I've setup this little company as an S-Corp or LLC with a tax ID).

I cannot be more SERIOUS when I say I WANT and NEED ideas, critiques and corrections as this project develops.

Price? I have no experience in this area. None. I will tabulate my material costs for each unit and go from there. Probably naively, I do not intend to include development costs, only material and a reasonable profit to make it worth my while.

I will say this: My goal is to make a powered model whose retail cost is surprisingly low.

-Brian / Cedar Rapids, Iowa
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Re: Chapman GP7 Project

Postby Bernd » Sun Jul 03, 2016 11:39 am

Brian,

Like what your doing here. I'll try to give you a hand as best I can.

Couplers: I'd say follow what has worked well on HO models for mounting Kadee couplers. Except us the dimension for N scale or what ever coupler looks good on TT scale. I think it was talked about in one of the threads.

Metal for frames. I'd say go with what is used on models today. You are never going to find an ideal metal for easy drilling. Go with what casts best.

Steam Engine: Yes, a 100% definite there. I also have Gordon Odegard's 2-8-2 (MR 1982-'83). I'll have to dig it out once I get back home from camp. There are also some issues from the 50' and 60's with articles similar to Gordons.

I'll add more to the thread as I get ideas to pass along.

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