MANTUA 2-8-2 MIKADO

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Actually I believe the eccentric should be 13° forward with the side rods down, BUT a check of my steamers did vary, and as you can see by the attached pic, even one of my brass engines was pretty much straight up with the side rods down. After all, they were built by "professionals" , not us fat fingered Americanos.
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kbkchooch said:
Actually I believe the eccentric should be 13° forward with the side rods down, BUT a check of my steamers did vary, and as you can see by the attached pic, even one of my brass engines was pretty much straight up with the side rods down. After all, they were built by "professionals" , not us fat fingered Americanos.View attachment 241791
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I would love to see the rest of that steamer.
 


Ok, it seems that it can be either way. I know that the closer the offset to the axle, the less the valve rod moves. I need to get a hex driver for the nut before I round the dang thing out. I measured at 3/32".

Thank youz twoz!
 
Kusojiji said:
Ok, it seems that it can be either way. I know that the closer the offset to the axle, the less the valve rod moves. I need to get a hex driver for the nut before I round the dang thing out. I measured at 3/32".

Thank youz twoz!
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Well, the design of the steam distribution will dictate the placement of the small end of eccentric crank. What @kbkchooch presented was an obvious missallingement. The eccentric crank is one of the pieces which causes the valves to open and close properly in order to admit steam into the cylinders, so it can not be alinged with the center of the wheel axle.
 
KriegslokBR52 said:
Well, the design of the steam distribution will dictate the placement of the small end of eccentric crank. What @kbkchooch presented was an obvious missallingement. The eccentric crank is one of the pieces which causes the valves to open and close properly in order to admit steam into the cylinders, so it can not be alinged with the center of the wheel axle.
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Like I said,, it was made by "professionals" ;) It looks like it was soldered in place, so I wouldn't dream of moving it.
 


Probably to be prototypical, the eccentric should be about 13 deg. forward of the axle center on both sides. (Not sure how you measure 13 deg. exactly on the model, just so both sides are the same or nearly so.) But, depending on how well the model valve gear is assembled, you may get smoother running with the eccentric nearly centered.
kbkchooch said:
Very nicely done!

I love messing with the old Mantua metal steamers. You can also make the Mikado into a (close to) USRA light Mikado by swapping the boiler and steam chest from a Mantua Pacific!

View attachment 241562
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Nice job!
 
trailrider said:
Probably to be prototypical, the eccentric should be about 13 deg. forward of the axle center on both sides. (Not sure how you measure 13 deg. exactly on the model, just so both sides are the same or nearly so.) But, depending on how well the model valve gear is assembled, you may get smoother running with the eccentric nearly centered.
Nice job!
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By eyeballing it, of course!!

Really, you guys have made me go look at a few locos. Some of the brass engines are spot on, some a little off. My mid fifties Penn Line Atlantic that I rebuilt with new Bowser valve gear is spot on! Now what was I saying about "professional" builders?? :D ;)
 
RGR, copy all. ~13 degrees leading the wheel. I think there was a utoob video of a valve gear in motion. I just want this thing to run smoothly really, so I may cheat a bit and make the valve move less than more.

Thanks all! And look forward to some photos... :)
 
Kusojiji said:
Nice!

I'm taking a look at the mikado today. I bought a 2.5mm nut driver but it doesn't fit. I think the mikado is 3/32 rod nuts. Don't really want to do the spanner again.
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When my Dad and I built the first Pacific from a kit, it came with a stamped steel wrench for the drive rod /wheel bolts. 50 years later I still have mine. No measurement marks on it to tell what proper size it is.
 
Nice! The bad thing about being overseas is that SAE stuff has to be ordered from the states, or pay buku bucks for it.

I got the mikado running. It turned out to be the motor commutator being gunked up. Don't know why since it is a new motor, but I pulled out a brush, cleaned the commutator with IPA, scraped out the gunk from between the whatever those things are called that the brushes ride on, and got it to run at the .20 amps that it used to run at.

Question that I have is why would the motor gunk up like that so quickly. Is the motor struggling? I don't think so since the amperage remains low while running. Oh well, will see as it goes.

As for the valve eccentric, will work on that when I can get a good driver.

Currently running around the room pulling 9 box cars.
 


Kusojiji said:
Nice! The bad thing about being overseas is that SAE stuff has to be ordered from the states, or pay buku bucks for it.

I got the mikado running. It turned out to be the motor commutator being gunked up. Don't know why since it is a new motor, but I pulled out a brush, cleaned the commutator with IPA, scraped out the gunk from between the whatever those things are called that the brushes ride on, and got it to run at the .20 amps that it used to run at.

Question that I have is why would the motor gunk up like that so quickly. Is the motor struggling? I don't think so since the amperage remains low while running. Oh well, will see as it goes.

As for the valve eccentric, will work on that when I can get a good driver.

Currently running around the room pulling 9 box cars.
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When I needed a nut driver, I found brass hex tubing, cut an inch off the tubing, and soldered a small brass rod across one end to make a nut driver.
 
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