The image below is of the drivers of a Soviet-era Er-class 0-10-0 displayed as a monument in Khvojnaya, Russia.

My question concerns the gadget near the rearmost driver. There's a sort of v-shaped bracket with something on its end, and some kind of bracket that may be intended to connect to the gizmo on the crankpin of the rear driver.

Is this part of a speedometer? I see them often, but not universally on the Er class locomotives. If a speedometer, why? The locomotive's top speed is reportedly less than 40 km/h. Dunno. But would welcome more information.

I seem to recall something of this configuration on other locos being set up as some kind of feedwater pump driven off the back axle.

A cursory look at what books I have on Russian steam and what I can scare up on a rudimentary Google search turns up empty. I may have a chance to do some research tomorrow in more books on the category of "Red Star steam"......

Hi Steam information
I was just up on youtube watching Russia Steam 2016, I saw at least four different locomotives with the same Gadget. I will have to agree with Alexander on the second post it is a speedometer.

Товарищи, вот ссылка на более раннее обсуждение подобного устройства! Консенсус состоял в том, что это действительно спидометр.


http://www.rypn.org/forums/viewtopic.php?f=1&t=35485&

From Google translate:
Comrades, here is a link to an earlier discussion of such a device! The consensus was that it really is a speedometer.

I am not as facile in technical Russian, but as a participant in the cited thread, I can say with some assurance that the Alco linkage described therein was NOT a speedometer drive.

The situation for the Russian example is different, and I think likely -- the most interesting part being the illustration on the P36 of how the part of the drive from the little bracket on the rod pin to the gearbox in line with the axle center is arranged. If I understand the picture correctly this is very thin, probably flexible, and would be an accommodation for suspension movement where the gearbox does not move. Compare this with Reidinger drive or the 'drive arm' version of Franklin rotary-cam drive (where the angular 'fidelity'between axle and shaft rotation is much more important).

On a locomotive with trailing truck, there's space for the speedometer drive shaft to pivot at the rear, and be (flexibly) suspended at the front to work with the suspension. On the 0-10-0 an accommodation of that kind wouldn't function as it would 'load' axially, which would require splines and other pieces, so it is constructed as a braced structure instead of a hinged 'bar'. Perhaps someone can provide close-ups of the pieces that connect the rod bracket to the gearbox.

Hi All
I found an of a closeup showing a Russian type speedometer used on steam off of Wikimedia. The only difference in this shot the crank is attached directly to the driver, instead of coming off and eccentric. The locomotive the photo is taken from is Russian class C68 according to information off Wikimedia.

Then there must be an arm missing from the shaft of the gizmo that would ride in the hole in the crank. Why would they require a speedometer? Anybody with a watch and mileposts ( or Km posts) can figure that out, and after some experience "just know" close enough......

The biggest argument against the speedometer theory is that the Russian 0-10-0's were extremely utilitarian freight locos, literally the equivalent of an RS1 or GP9 in the diesel era. I'm extremely hard-pressed to imagine one of these things in any service where a speedometer would have been necessary. Those who have handled the likes of CN 7312 or Frisco 1630 at any kind of speed can probably attest that these 0-10-0s would have been rough-riding brute at anything above a drag speed.

I remember seeing these in the USSR, I believe they drive a speed indicator/recorder. A small drive arm on the suspended gear box projects with substantial clearance through the hole in the bracket that is attached to the rod pin. This transfers the wheel rotation to the gear box outboard of the motion of the rod. The sloppy fit allows for changes in the geometry that occur constantly with ride dynamics and also moves the contact point around on the drive arm. The drive arm is easy to replace if damaged and the system is not as subject to interference from snow and ice packing as a drive that rides on the tread or as vulnerable as a flexible cable drive.

PC

We did put speedometers in RS1s and GP9s. Still not certain it makes it necessary.....