Friday, 16 October 2015

Update oktober 2015

For the little NSB type IV I have received four drivers and a cab with sidetanks 3D printed in high detail stainless steel from Imaterialise. The wheels (without rims) but with integral half axle came out quite well. The turned steel wheel rims in the picture I have already pushed onto the wheels. These rims are from THE 2MM Scale Association (2MMSA). They where pressfitted from the back onto the wheels with handforce.

                 Size compared to 1 Euro

Price for 3D print of a set of 4 wheels was  Euro 19.79/ £ 14.64.
With the steelrims the tota price become:  E 23.84/£ 17.64
2 pair of 2MMSA 7mm dia drivers is E 18.90£14.00

Comparison with 7mm DIA coach wheel (left)and 7mm DIA driver (right) from the 2MMSA

 I have also received from Shapeways a set of wheels from the same stl. file. This time in Frosted Extreme Detail plastic. Of cause plastic half axle may not be so good, but for a stand model its okay and I wanted to compare with the steel ones. The cost for the set shown without steel rims was: E 10.76/ £ 7.96

Steel wheels with steel rim attached
As you can see from the photos the degree of detail and fineness is about equal between steel and plastic. Further development of the plastic solution could be to have steel axles and steel rims. But to assemble three part and get a wobblefree wheel is a real challenge! Pickup would then be from the steel rims and therefore not really suited to split frame pickup from the axle.

I will go further with the steel version for this project. I have two ideas:
Use separate wheel rims turned in steel from 2MMSA. I will ask them to make a version where the little flange that keep the wheel in the right position is made on the inside and not on the outside.. The 1mm integral half axle, I will increase to 1.5mm and turn it down to 1mm for accuracy.
Alter the STL. file to incorporate the flange a little over scale and then turn it down to the right profile.  The 1mm integral half axle, I will also here increase to 1.5mm and turn it down to 1mm for accuracy.
So to the  cab/sidetanks:

Imaterialise warned me that this may not work out well because of thin walls and the general shape. They where right:

They were able to produce the thin wall (0.3mm) but the model wharped in the prosess. If I shall go furter with this I will try thicker walls and put in preliminary reinforces like closing the cabsides and connect the two sidetanks. By using tabs to connect , It should be easy to cut off the reinforcements.

Comparison with 1 EURO

Silhouette makes the warping evident

The steps from the cab came separate.

To conclude this, I also ordered a plastic version from Shapeways, but they refused the design. I prefer the metall version because I need all the weight I can get for traction. Therfore I will continue developing the metal version or go back to etching this part

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