Author Topic: A gearbox for a little locomotive  (Read 14502 times)

Offline Zephyrin

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A gearbox for a little locomotive
« on: February 21, 2022, 10:08:10 AM »

This is about a little gear box for a next project, another small gauge locomotive powered with a 4 st engine...

this gearbox looked quite simple, simple enough to be made very close to the original, and if the rail gauge is 45mm, the spur gears are between 38 & 15 mm, easy to cut with a module between 0.5 and 0.75.

it is something that I thought to be fairly simple, but I underestimated the loss of gray cells when getting older,
and I can't get the succession of gear wheels involved in each position of the 2 selector forks...
how to obtain low and high gear together with for and backward run, as moving either of the lever leads to engage the clutch ?
between idle and leading wheels, i'm out of touch in fact !

Offline Roger B

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Re: A gearbox for a little locomotive
« Reply #1 on: February 21, 2022, 11:18:15 AM »
As I see it the engine drives the large gear on the first shaft which then drives the small gear on the second shaft. The shafts will then turn in opposite directions at different speeds.
The speed is selected by engaging one of the shafts with one of the equal size gears in the middle. These are free running on the shafts.
The direction is then selected by engaging one of the smaller pinions with one of the equal size gears (which will be turning in opposite directions) which engage with the large gear below.

I think that I have seen a model similar to this in Maschinen im Modellbau  :thinking:
Best regards

Roger

Offline Admiral_dk

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Re: A gearbox for a little locomotive
« Reply #2 on: February 21, 2022, 11:30:20 AM »
I see Roger just beat me to the answer.

The important thing to understand is that the two equal sized gears in line with the center crank line are freewheeling on the shafts (like the two smaller ones just below), until one of them are locked to the shaft with the two moving gearless wheels on top of the draving (connected to the High/Low selector handle). And the shafts are locked to the gear wheels on the bottom.

Funny - I can't find any clutch on the drawing.

Per
« Last Edit: February 21, 2022, 06:06:26 PM by Admiral_dk »

Offline Roger B

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Re: A gearbox for a little locomotive
« Reply #3 on: February 21, 2022, 11:38:38 AM »
I believe that the clutches are the fast and slow gear selectors. I have driven some German narrow gauge locomotives with this system. In the cab picture the hand wheel operates a screw mechanism to engage either clutch. The hand lever in the gear diagram is not correct.
Best regards

Roger

Offline Roger B

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Re: A gearbox for a little locomotive
« Reply #4 on: February 21, 2022, 11:48:45 AM »
This was the build I was think of:

https://www.vth.de/maschinen-im-modellbau/unsere-beitraege/minenlok-mit-verbrennungsmotor

If I remember correctly the ignition System was in the log wagon.
Best regards

Roger

Offline Vixen

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Re: A gearbox for a little locomotive
« Reply #5 on: February 21, 2022, 11:50:18 AM »
Hello Zephyrin.

My take is similar to Roger B's. However I think both levers are shown in the mid position, ie, with neither fwd/rev or fast slow selected. You can see the fwd/ rev gears shown partially overlaping the lower gear. When one of the levers is moved, it moves two of the dog clutch gears ; one move inwards and engages the drive dog clutch while moving the gear central, the other moves outwards disengaging that gear.             Each lever moves two gears and their dog clutches.

The full size engine with it's big flywheel should have been able to tick over quite slowly and the loco would move off slowly when the levers engaged the drive. Model engines tend to run at a much higher speed so engaging the dog clutches could be interesting.

Did you see I recently posted the drawings for my two speed/ rev gearbox on the Westbury Seal topic?

Cheers :cheers:

Mike
« Last Edit: February 21, 2022, 12:11:58 PM by Vixen »
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Offline Roger B

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Re: A gearbox for a little locomotive
« Reply #6 on: February 21, 2022, 12:34:04 PM »
Hello Mike,

If you closely at the gear diagram forward and reverse are dog clutches, fast and slow are cone clutches. Selecting the speed ratio via a clutch was quite common narrow gauge loco practice. The Ruston and Hornsby gearbox selected the three speeds with individual clutches via a lever. O&K used a system similar to that above.
Best regards

Roger

Offline Zephyrin

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Re: A gearbox for a little locomotive
« Reply #7 on: February 21, 2022, 03:10:08 PM »
Hi,
Thanks for these answers, very helpful!
I had to admit that I can't figure out how to make this gearbox design by myself, this is somewhat frustrating, as I can't see these gears running just by thinking.
I can't upgrade my brain.
Fortunately, skills here are fabulous, and that at first glance experienced modelers know and understand how it works, this is so helpful.

on my previous loco, I simply did a friction drive, with continuously variable speed in both direction, the principle being much simpler...and my "diesel" shunter is a pleasure to  run on the track at the club, and I like to open the bonnet to see and show its inards.
<a href="https://www.youtube.com/watch?v=VwDeO6ktf7A" target="_blank">http://www.youtube.com/watch?v=VwDeO6ktf7A</a>

But a geared speed box is a step ahead, mechanically more interesting to do, as far as I understand the functioning !

Yes Roger, this is exactly the type of loco I plan to make. The model published in "Maschinen im Modelbau" is beautiful, I do have a copy of the full paper, very inspirating.
Yes, Vixen, I followed the seal build, and its gearbox too, I hope it will make me clever, it may works at the end !

In fact, I'm still in the project stage, but already if I understand how to make a simple 2 speed gearbox plus reverse, I'll be relieved!
« Last Edit: February 21, 2022, 03:14:38 PM by Zephyrin »

Offline Admiral_dk

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Re: A gearbox for a little locomotive
« Reply #8 on: February 21, 2022, 06:59:49 PM »
That is almost cheating Rodger .... having read the original build article - the link is a dead give-away :Lol: 

I must admit that I can't deduct the Cone-Clutches in the drawing - I can see that they aren't Dog-Clutches as  Forward and Reverse .... But it makes perfect sense that they are clutches and works as you describe.

I also agree that both "Levers" are in "Neutral" in the bottom drawing.

Interesting Shunt Loco - I will certainly follow  :cheers:

Yes - I remember the build of the one in the video Zephyrin  :ThumbsUp:

Offline steamer

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Re: A gearbox for a little locomotive
« Reply #9 on: February 21, 2022, 07:48:37 PM »
GailNM built a small loco powered by a "tiny" engine.    It wasn't that long ago.   

Dave
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Offline Dan Rowe

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Re: A gearbox for a little locomotive
« Reply #10 on: February 21, 2022, 08:05:00 PM »
Dave the gas loco Gail built was a model of the Hornsby-Akroyd oil engine 0-4-0 Lachesis which was supplied to the Woolwich Arsenal in 1896. This was an 18" gauge line the model is 7/8" scale on 32mm track.

Cheers Dan
ShaylocoDan

Offline steamer

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Re: A gearbox for a little locomotive
« Reply #11 on: February 21, 2022, 08:19:34 PM »
Dave the gas loco Gail built was a model of the Hornsby-Akroyd oil engine 0-4-0 Lachesis which was supplied to the Woolwich Arsenal in 1896. This was an 18" gauge line the model is 7/8" scale on 32mm track.

Cheers Dan

That may be, but I know he made one with  Tiny hit and miss engine in it....maybe O or G gage....
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Dan Rowe

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Re: A gearbox for a little locomotive
« Reply #12 on: February 21, 2022, 08:35:19 PM »
Yes Dave we are talking about the same loco with a Tiny hit and miss engine. Gail made a small batch of these and I missed out.... :facepalm:

Cheers Dan
ShaylocoDan

Offline Zephyrin

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Re: A gearbox for a little locomotive
« Reply #13 on: February 22, 2022, 08:58:56 AM »
Yes Gail Graham (GailNM)  built 2 different loco for 7/8 scale, both powered by the "Tiny" H& M engine, the Woolwich and a Baldwin loco, visible on his Utube channel "nmsteam". He built more than a dozen of these models !
https://www.youtube.com/user/nmsteam/videos

The realistic point is that with an H&M engine, the tickover sound at idle is really close to the original loco, in spite of a larger rpm.

Thanks again for these explanations. I clearly understand now how this gearbox works...
I had completely missed the presence of a hidden second set of clutches the cone clutches unravelled by Roger in the upper set of wheels (langsam/schnell)
The wheels are free on the 2 rotating axles when not engaged by the dog or cone clutches.

I can also buy one of the cheap plastic gearbox for rc cars and trucks, simply to look inside...if it is simpler before cutting gears, there is a lot of teeth to carve !

Offline Zephyrin

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Re: A gearbox for a little locomotive
« Reply #14 on: March 07, 2022, 10:10:39 AM »
Hi,
I found on the Net a page about the restoration of one of these small Deutz narrow gauge locos, with a description of their transmission!
thanks again for your explanations, the only point that differs is that the clutches are not cone clutches, but wrap spring clutches (Schlingfederkupplung), not that simple to get them working in model, I think to be satisfied with a simple soft friction drive with an O-ring…

http://gillbachbahn.bahnwiki.org/index.php5/FWM_Lok_35
http://gillbachbahn.bahnwiki.org/images/b/b7/C14getrb.PNG

 

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