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Author Topic: 3D printed chassis experiment  (Read 10725 times)

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Offline EtchedPixels

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3D printed chassis experiment
« on: January 30, 2012, 02:04:20 PM »
I've been working on trying to make easy to build model locomotive chassis for a while with various etched designs but not really made anything much easier than current designs.

This time however it's 3D print based - which has the advantage of not conducting electricity but the disadvantage of low weight.

OpenSCAD designed N scale chassis. Need to order the other drive wheel and drive band. I also probably need to make it two join together parts to deal with the topological inconveniences in the design (notably you have to disassemble the drive shafts entirely to change the band).

"Knowledge has no value or use for the solitary owner: to be enjoyed it must be communicated" -- Charles Pratt, 1st Earl Camden

Offline Stew2000

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Re: 3D printed chassis experiment
« Reply #1 on: January 30, 2012, 03:24:49 PM »
It's an interesting way of making a chassis.

Offline dodger

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Re: 3D printed chassis experiment
« Reply #2 on: January 30, 2012, 06:12:27 PM »
Very good and novel design.  Will it be suitable as a motor bogie for multiple units?

Offline Tank

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Re: 3D printed chassis experiment
« Reply #3 on: January 30, 2012, 06:45:40 PM »
Will it be suitable as a motor bogie for multiple units?

Just what I was thinking!  :)

Offline EtchedPixels

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Re: 3D printed chassis experiment
« Reply #4 on: January 30, 2012, 10:24:01 PM »
For a motor bogie it's somewhat easier as there will be room to put the other drive wheel at the end (solving all the 'how to get a band on' problems) and also letting you get it down to 8'6 wheelbase (that one is 10' for a tender). I think a bigger motor would be a good idea given the choice.

I also need to sort out making it two clip together parts and I guess for a motor bogie also printing the bogie outers as part of the block

Early stages yet, but yes I think its doable and you can certainly print a pivot on the top of it and the like. More tricky would probably be getting the coupling arrangement right given the 1mm wall thickness required.

I want to get the basic unit working first, and stuff it under a few things before I start trying to get that clever !

Alan
« Last Edit: January 30, 2012, 10:26:39 PM by EtchedPixels »
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Offline EtchedPixels

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Re: 3D printed chassis experiment
« Reply #5 on: February 03, 2012, 09:58:30 PM »
Next bits sent off for the next experiment.

Things I learned

- the basic materials are up to it
- the accuracy is good enough to grip the motor well, hold the shafts properly
- its flexible enough you can indeed clip shafts into place the way things like Farish wheels work

I also learned that

- 5mm pulley wheels are 5mm diameter in the centre where the band goes, and 6mm on the outside, and in fact about 6.5mm with the band on. Oops.. slight fit problem, and using a 3mm pulley means length issues and gearing problems

- Physics applies. When the worm tries to turn the wheel the worm itself gets pushed back and the drive shaft moves because it has play. This makes the worms rub up against the plastic. Given the material is rough I think fine washers might actually be a better idea here.

- Just because you can print it in one part doesn't mean its a clever idea assembly wise. So the motor bogie attempt that's just gone for printing clips *round* the drive shaft so you don't need six hands to assemble it.


More news when the postman delivers 8)
"Knowledge has no value or use for the solitary owner: to be enjoyed it must be communicated" -- Charles Pratt, 1st Earl Camden

Offline Lawrence

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Re: 3D printed chassis experiment
« Reply #6 on: February 03, 2012, 10:31:30 PM »
Keep it coming Al, interesting project  :thumbsup:

Offline Stevie DC

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Re: 3D printed chassis experiment
« Reply #7 on: February 04, 2012, 08:45:07 PM »
Hi Al,

That looks really good!  :thumbsup: I've seen someone on RM web try this with a 4mm steam loco chassis and am now very interested in trying this myself.

I take it that this is printed in a SWF type material?

P.S. Arn't those micro motors great!  8)

Offline EtchedPixels

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Re: 3D printed chassis experiment
« Reply #8 on: February 04, 2012, 08:51:19 PM »
I take it that this is printed in a SWF type material?

P.S. Arn't those micro motors great!  8)

I printed one in detail and one in SWF as I wasn't sure what would work best. The SWF one was both the cheapest ( < 2.50) and best to work with.

I think its a very workable medium for chassis except for the weight.

I do like the micro-motors although if the next test works I need to think hard about whether a 10x12 12v motor would be more appropriate and if I can make some kind of interchangable tops for the drive part so you could pick between motor mounts or even just a drive shaft and universal joint (which  I'm hoping I can also print !)

Alan
"Knowledge has no value or use for the solitary owner: to be enjoyed it must be communicated" -- Charles Pratt, 1st Earl Camden

Offline Stevie DC

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Re: 3D printed chassis experiment
« Reply #9 on: February 05, 2012, 06:39:54 PM »
Go to here about SWF. I've tried this and stainless steel (which wasn't particularly accurate and a pain the clean up!) however I've struggled to get the wheels turning freely. I've previously used 1.5mm diameter slots for the axels but feel that 1.6mm would be better. What size did you use?

Re the weight - if you make the motor mount hollow and open at the top you should be able to fill the space with liquid lead, might not add much but every little helps!

Offline EtchedPixels

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Re: 3D printed chassis experiment
« Reply #10 on: February 05, 2012, 08:31:35 PM »
Go to here about SWF. I've tried this and stainless steel (which wasn't particularly accurate and a pain the clean up!) however I've struggled to get the wheels turning freely. I've previously used 1.5mm diameter slots for the axels but feel that 1.6mm would be better. What size did you use?

Re the weight - if you make the motor mount hollow and open at the top you should be able to fill the space with liquid lead, might not add much but every little helps!

1.6mm with 1.5mm axles, and I also ran a 1.6mm drill through the holes to polish them. Making the chassis walls as thin as allowed around the axle also reduces friction considerably. A 0.7mm wall even only for the 0.5mm closest to the axle will make a difference. The other option which I've not explored yet is to use the 2mmSA bearings.

The hollow isn't a bad idea. I found someone else doing this for non rail stuff and he puts screwhole sized holes in various places on this drive unit so that he can screw stuff into it to adjust the balance and weight.

My first targets are both white metal bodies so hopefully I can ignore the issue this time and fight it later.

Alan
"Knowledge has no value or use for the solitary owner: to be enjoyed it must be communicated" -- Charles Pratt, 1st Earl Camden

Offline Stevie DC

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Re: 3D printed chassis experiment
« Reply #11 on: February 06, 2012, 01:18:34 PM »
Thanks for the info Alan,

Will be watching with interest to see how this works out for you.

One thing that occured to me was the properties of WSF would the direct contact with the axles and drive components wear them down too quickly? To be honest with the cost of SWF as long as the drive components could be salvaged it might not be too much of a problem...

Hmmm, maybe a printed gearbox designed to fit around an etched box for the chassis with coupling rods, etc.....  :evil:

Offline EtchedPixels

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Re: 3D printed chassis experiment
« Reply #12 on: February 08, 2012, 10:20:45 AM »
I'm working on the basis that they will be cheap enough to wear out and replace, and probably get cheaper and cheaper. And since the design isn't dependant on Bachmann or Dapol happening to have spares available it's not a problem in the same way.
"Knowledge has no value or use for the solitary owner: to be enjoyed it must be communicated" -- Charles Pratt, 1st Earl Camden

Offline EtchedPixels

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Re: 3D printed chassis experiment
« Reply #13 on: February 15, 2012, 10:33:27 PM »
The motor bogie has arrived. It's assembled and can sort of drive. Various small adjustments and thinkos need fixing to make it useful but it sort of proves the concept. Rev3 adjusts some clearances and adds a needed bearing at the non motor end to stop the shaft jumping over the worm.

And yes.. that's a NEM pocket as an experiment !

"Knowledge has no value or use for the solitary owner: to be enjoyed it must be communicated" -- Charles Pratt, 1st Earl Camden

Offline polo2k

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Re: 3D printed chassis experiment
« Reply #14 on: February 16, 2012, 01:54:05 AM »
nice!
Cheers
-Ash-



The only way to guarantee failure, is not to try

 

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