Chapman GP7 Project

Re: Chapman GP7 Project

Postby ConducTTor » Sat Oct 01, 2016 10:10 pm

Hahahaha!
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Re: GP7 Motors on Chassis

Postby ConnRiver » Fri Oct 07, 2016 6:54 pm

Here are GP7-9 chasses, one with a Mitsumi M15N-3 motor, the other with a Mashima 1020D motor. The dark gray areas indicate the overlap between motors and chassis frames. It appears either motor can be easily accommodated.

The vertical Yellow lines mark the chasses center lines. The Red lines indicate the center of the fuel tank sub-chasses (metal). The fuel tank is off center. This results in two different lengths of drive shafts from motors to worms. This isn't a problem?

(BTW, the light gray rectangle around the fuel tank denotes the plastic outer shell of the tank.)

I've drawn both motors in 3D but thought the 2D elevation view above reveals motor locations better.

68 - GP7 ph I - Chasses-Motors.jpg

Oh, the horizontal black lines running from the motor axles to the worms mark drive train height only, they do not indicate actual drive train linkage. I'm gonna ask for helpful suggestions when it comes to that.
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Re: Chapman GP7 Project

Postby ConducTTor » Fri Oct 07, 2016 9:24 pm

The different length driveshafts are no problem. You can di the driveshafts cheaply and easily with RP - something like WSF from Shapeways. All you do lengthen/shorten to accomodate the motor. The Mashima is
obviously smaller - that allows for more weight under it and more space above it for electronics or even a speaker. It would be my pick.
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Re: Chapman GP7 Project

Postby sd80mac » Sat Oct 08, 2016 5:51 am

The project looks really good so far. You are making great progress! I'm sorry I haven't had much time to contribute as I am building a workshop in the backyard, but keep.up the good work! I've also noted that you made provision for the Mitsumi motor in addition to the Mishima. Good move! According to our overseas modeling counterparts, it is a good repowering option.

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Re: Chapman GP7 Project

Postby ConnRiver » Sat Oct 08, 2016 9:28 am

ConducTTor wrote:The different length driveshafts are no problem. You can di the driveshafts cheaply and easily with RP - something like WSF from Shapeways. All you do lengthen/shorten to accomodate the motor. The Mashima is obviously smaller - that allows for more weight under it and more space above it for electronics or even a speaker. It would be my pick.


One driveshaft that slides into the other section, trim to fit? That would work well.

Haven't done it before, but I need to assign a material to the various chassis/frame components. The 3D software will report the weight as the build continues. Rolling stock weights we know, do we know what an ideal weight is for a loco of this and that dimension?

Who here wants to become a Mashima dealer? We've got to find better prices than $40-plus per 1020D. The M15N-3 is under $5 per unit.
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Re: Chapman GP7 Project

Postby ConnRiver » Sat Oct 08, 2016 9:35 am

sd80mac wrote:The project looks really good so far. You are making great progress! I'm sorry I haven't had much time to contribute as I am building a workshop in the backyard, but keep.up the good work! I've also noted that you made provision for the Mitsumi motor in addition to the Mishima. Good move! According to our overseas modeling counterparts, it is a good repowering option. -Donnell


Donnell, hey, figured you were off on extended vacation ;-) Building a workshop, that doesn't sound like va-ca.

I think it best to accommodate both motors . . . maybe let the modeler choose? Design for the deeper-sitting Mitsumi, provide a pad for the Mashima. Test the chassis with each motor. Over at the repowerandregear group, those guys have discussed chassis testing on and off. Useful information.

The cost of the Mashima continues to eat away at my gut. . . .

Oh, wanted to mention that, according to the respective spec sheets, the motor shafts of the two motors vary a tiny bit. One is .05955" diameter, the other .05905" diameter. The same likage can fit both, what with only .0005" difference. I can assume a .060" diameter motor shaft (same as wheel axle diameter), can't I?
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Re: GP7 Project - Motor attachment

Postby ConnRiver » Sat Oct 08, 2016 9:43 am

Is it necessary to fix the motor by screw(s) to the chassis? Would not sticky double-sided 1/8 inch foam tape work?
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Re: Chapman GP7 Project

Postby ConducTTor » Sat Oct 08, 2016 12:34 pm

The tape would work but you need it on top and bottom. As for the drive shafts, while you can have one half slide in and out of the other, I didn't mean that. I meant with cad software it's easy to lengthen/shorten it and if you're using RP, there is nothing else to do - just print.
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Re: Chapman GP7 Project

Postby krokodil » Sat Oct 08, 2016 12:45 pm

You can design some clamps to hold the motor in place (different for both motors).
Check also the NWSL universals, they have just the universals from engineerig plastic, the ball head is on metal rod ( about 2mm in dia) so it is very easy to adjust the length.
There is no ideal weigth for locomotives. The goal is to make them heavy as much as possible. Luckily in TT we cannot make the locomotives very heavy, what could effect the wheel bearings. However I would recommend to make the frame from white metal. If it is made from plastic one will never reach the optimal weigth and the best performance specially for long US trains.
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Re: GP7 Project - Motor attachment

Postby areibel » Sat Oct 08, 2016 3:27 pm

ConnRiver wrote:Is it necessary to fix the motor by screw(s) to the chassis? Would not sticky double-sided 1/8 inch foam tape work?

Or a little black RTV silicone and glue the motor down, it gives you a little time to get it aligned but holds securely when set. And it's easy to slice it with a blade to free the motor if necessary.
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