Loco Frame - Truck Gearing

Re: Loco Frame - Truck Gearing

Postby ConnRiver » Fri May 27, 2016 8:59 am

So, I need to tear down my MTB SW1200 to discover how it ticks. . . . Hope it's easily disassembled, I've not run it yet, not having TT track.

I'm 2D then 3D drawing all the components of the power chassis (I've finished the Mashima 1024D and flywheels, will tackle the frame next). If friends here will comment, I'll start a separate thread with screen shots of each step; I'd like suggestions/corrections as I move along. When finished with the drawing, I'll start CNC cutting.

This sound OK? Any objections?

(Note: What does the 'D' in 1024D signify? That motor is good to go for us, correct?)

-Brian C. / Cedar Rapids, Iowa
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Re: Loco Frame - Truck Gearing

Postby areibel » Fri May 27, 2016 9:11 am

The SW1200 is pretty basic, but just be careful when removing the little wire clip that holds the truck into the chassis. I think I put one into orbit when it flew, in a 10 by 12 room it completely disappeared!
A friend gave me a tip, intended for Kadee springs but I think it'll work for this too- A big sheet of plastic wrap (like Saran Wrap). Take a piece about 2 feet long and drape it over what you're working on, you can keep your hands under and anything that flies won't go too far.
I found some at the dollar store that's probably 18 inches wide, it's worked so far!
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Re: Loco Frame - Truck Gearing

Postby krokodil » Fri May 27, 2016 10:01 am

Hi Brian the D on Mashima motor code means double end. ( two axles). It is a nice project.
Greetings from Austria
E.T.
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Re: Loco Frame - Truck Gearing

Postby ConnRiver » Fri May 27, 2016 12:42 pm

krokodil, thanks for decoding the 'D' for me. Shoulda known, but didn't think of it.

Al, I removed the PCB by clipping the wires near the board, leaving wire "tails" soldered to the wire clips. Put them in a baggie to prevent them from escaping.

Still, I don't know how to remove the truck itself from the frame. I've tried some gentle and not so gentle prodding, but no good. An exploding diagram might have been helpful for this. . . . If you or someone else here has removed a truck or trucks from the chassis frame, please give me pointers.

Thanks, Brian C. / Cedar Rapids, Iowa
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Re: Loco Frame - Truck Gearing

Postby areibel » Fri May 27, 2016 1:40 pm

Hi Brian,
if you look across the top of the truck, about an eighth of an inch back from the drive shaft socket you'll see a piece of black wire running across the truck. Look closely at that, it's a clip that runs down the sides of the gear tower and then turns inward towards the motor- that's the clip that holds the truck in. you can spread it slightly and it will pop off of the truck, and then you can drop the truck through the frame. But as I said, they do like to fly so take a little care!
If I ever have the money to build a model workshop, I think I'm going to paint it all white from floor to ceiling so I can find the UFOs I launch!
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Re: Loco Frame - Truck Gearing

Postby ConnRiver » Fri May 27, 2016 3:17 pm

Ahhhh-ha, I misunderstood which wire would go flying! That did it, I've got the truck disassembled. The final spur gear has 12 teeth, so it's a 12:1 gear train.

The worm appears to be brass, the worm gear (compound) and four spur gears (two idle) appear to be nylon, or nylon-like.

Thanks! Brian C. / Cedar Rapids, Iowa
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Re: Loco Frame - Truck Gearing

Postby sd80mac » Tue Jul 12, 2016 12:35 am

ConnRiver wrote:Ahhhh-ha, I misunderstood which wire would go flying! That did it, I've got the truck disassembled. The final spur gear has 12 teeth, so it's a 12:1 gear train.

The worm appears to be brass, the worm gear (compound) and four spur gears (two idle) appear to be nylon, or nylon-like.

Thanks! Brian C. / Cedar Rapids, Iowa


Hello Brian,

I spent the better part of this weekend researching gear design and gear ratio, and trying to work out the numbers for a GP Blomberg 4-axle truck. At first, I thought that I could just take all of the dimensions from the Athearn blue box truck and just multiply them by .725, thus shrinking everything to TT-scale. However, this would constitute making custom gears somewhere between module 0.35 and 0.4 in metric units, or not-quite DP72 in imperial units. I haven't converted my Sherline to CNC yet, so I can't cut anything, but I suppose I could draw them in 3D and have masters printed for resin casting.

Anyhow, the design is loosely based on the Athearn truck and uses a module 0.5 12-tooth plastic gear commonly found on eBay. It also retains the 12:1 gear ratio. The module 0.5 gears are fairly large for TT, but I think they would work. My initial thought was to machine the gear down to 2mm or 3mm thick to reduce their bulkiness, but on second thought, I think I will replicate the Athearn truck, and draw up the gears, and try the 3D printed version.

Donnell
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Re: Loco Frame - Truck Gearing

Postby gerhard_k » Tue Jul 12, 2016 1:48 pm

sd80mac wrote: ... the design is loosely based on the Athearn truck and uses a module 0.5 12-tooth plastic gear commonly found on eBay. It also retains the 12:1 gear ratio. The module 0.5 gears are fairly large for TT, but I think they would work. My initial thought was to machine the gear down to 2mm or 3mm thick to reduce their bulkiness, but on second thought, I think I will replicate the Athearn truck, and draw up the gears, and try the 3D printed version.

Donnell

In the GP7 thread, just a few days ago, both you and Brian mentioned the 14:1 ratio as being generally used. As we all know, with model locomotives, the problem is seldom inadequate speed but rather sufficient low-speed smoothness and control. So while your design is still fluid, you might consider a 14- or maybe even a 16-tooth gear, even if it will need smaller teeth to fit in TT. After all, how often will one of your engines want to be MU'd with another different engine, so that the absolute speed similarity will be important?
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Re: Loco Frame - Truck Gearing

Postby oldtrainguy » Tue Jul 12, 2016 2:43 pm

Wouldn't using 'off the shelf' gears be a better way to go?
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Re: Loco Frame - Truck Gearing

Postby sd80mac » Tue Jul 12, 2016 5:36 pm

oldtrainguy wrote:Wouldn't using 'off the shelf' gears be a better way to go?


Off the shelf gears would work fine, but finding an affordable and consistent source of parts is the issue. The most abundant size available is module 0.5, however they are a bit big for TT-scale. Module 0.3 to 0.4 would be a much better size, but again, availability is a major factor.

Donnell
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