Author Topic: A gearbox for a little locomotive  (Read 3144 times)

Offline Zephyrin

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Re: A gearbox for a little locomotive
« Reply #15 on: April 10, 2022, 03:24:59 PM »
Hi,
Here are the first parts of my next model, a small Deutz 4-stroke field loco for narrow gauge (600mm), at 1/13.5 scale, for 45 mm rails, from the images above.
I especially liked the transmission, and thanks to the help I received here on how the gearbox works, I was able to reproduce it faithfully enough, with the dog clutch system for both directions and the clutch on both shafts, fast and slow; the latter is done here by friction and cone instead of the spiral spring (Schlingfederkupplung), a bit too complex to miniaturize.
and I added a reducing stage because my engine will not be able to run at the speed of the original, 300-400 rpm !

This is not the chassis of my future loco, but just a first test "to see" if everything works well with recycled loco components...
I put a small dc electric motor and a battery to animate the whole stuff, the power varied from 0.5 W when idling to 0.8 W, for fast forward.


The whole thing is quite satisfactory, except the PLA 3D printed dogs, fried after these tests...
I still have to put a steering wheel for the speed clutch and a lever for selecting the direction gear to keep these couplings well engaged during the ride.

Then the engine, a small 4 stoke (about 2cm3) with long stroke, will be also quite interesting to make, the rest of the model being more conventional modelling!

Offline Johnmcc69

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Re: A gearbox for a little locomotive
« Reply #16 on: April 10, 2022, 04:40:21 PM »
 :ThumbsUp:
EXCELLENT!
 :popcorn:

 John

Offline RReid

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Re: A gearbox for a little locomotive
« Reply #17 on: April 10, 2022, 05:11:24 PM »
What a great little gearbox! I'm looking forward to watching this project develop. :ThumbsUp:
Regards,
Ron

Offline Zephyrin

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Re: A gearbox for a little locomotive
« Reply #18 on: April 11, 2022, 08:35:15 AM »
 thanks for the appreciations!
and thanks again for unravelling the mechanism of this transmission !

some pictures of the components.
I did first a set of 3d printed dog clutches, to see if they easily engage, but obviously they didn't last for long ! I hope the brass ones would last longer...I still have to make a new set with a slopped or staggered part in the dogs, as in the original drawings.
all the axles are mounted with roller bearing, to minimize drag in all these gears. I'm confident that my engine will cope with it.

Offline Admiral_dk

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Re: A gearbox for a little locomotive
« Reply #19 on: April 11, 2022, 11:10:37 AM »
A very convincing demonstration of the whole system  :praise2:

+ thank you very much for having the Deutch drawing in the background of the second to last picture - as it helped me to understand how the original clutch worked  :cheers:

Per

Offline Zephyrin

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Re: A gearbox for a little locomotive
« Reply #20 on: April 11, 2022, 06:40:24 PM »
 Ha ha, the clutch with the spiral spring, I replaced it by a friction drive... as I didn't understand the arrangement..

but recently I have found on the net the instructions for use for these little loco, with the setting of the spiral clutch, with 0.5mm of clearance between the drum and the spring, with the proper documentation the mechanism in now cristal clear even for me...
pressure on the disk push the little lever and reduces the diameter of the spiral spring which bind to the drum and drive the gear wheel...
It is very clever, but alas too difficult to miniaturize...but if everything goes, maybe I will have a go.



« Last Edit: April 13, 2022, 10:52:27 AM by Zephyrin »

Offline Admiral_dk

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Re: A gearbox for a little locomotive
« Reply #21 on: April 11, 2022, 10:30:47 PM »
Nice to see it in even bigger format - but you can actually se it in the picture I mention  ;)

Per

Offline Roger B

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Re: A gearbox for a little locomotive
« Reply #22 on: April 12, 2022, 05:10:20 PM »
Excellent  :ThumbsUp:  :ThumbsUp:  :wine1:

Some similar gearboxes were made with cone clutches, I think O&K may have been one of them. The spring type clutch, under the name Scroll Clutch was used in some early Mercedes Benz cars.

https://www.practicalmachinist.com/vb/antique-machinery-and-history/scroll-clutches-wrapped-spring-type-152483/
Best regards

Roger

Offline Zephyrin

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Re: A gearbox for a little locomotive
« Reply #23 on: April 13, 2022, 10:57:17 AM »
Thanks Roger,
the level of knowledge here is amazing !