Boston & Maine B15 2-6-0 Scratchbuild

[Spades]

He could sheet the tender in plastic,  Easy to scribe and attach the archer rivets

IMO, lightly scribed panel lines are very realistic. Not deep wide and deep grooves (like the Rapido did on the meat reefers), but gentle scribings on the brass walls.  This is where the realistic model making becomes art rather than simply exact science.  Totally smooth walls of the tender will look really strange (in person and in photographs).  Not only rivets and panel lines are visible but the tender walls aren't perfectly smooth.


Here are some additional photos which show panel lines on tenders. I'm not posting photos directly not to waste George's bandwidth.

http://www.rr-fallenflags.org/bm/bm-s1440afm.jpg
http://www.rr-fallenflags.org/bm/bm-s1445ewa.jpg
http://www.rr-fallenflags.org/bm/bm-s1455l.jpg
http://www.rr-fallenflags.org/bm/bm-s1455jpa.jpg
http://www.rr-fallenflags.org/bm/bm-s1484ssC.jpg

I have half a dozen on enlargements of this class of loco and they all claerly show panel lines and rivets on the tender.

[peteski]

He could sheet the tender in plastic,  Easy to scribe and attach the archer rivets

Sure, but brass is also fairly soft and easy to scribe.

[garethashenden]

He could sheet the tender in plastic,  Easy to scribe and attach the archer rivets

I prefer working with metal to plastic

Sure, but brass is also fairly soft and easy to scribe.

This is nickel silver, also easy to scribe.

[peteski]

This is nickel silver, also easy to scribe.

Yes, true.   I forgot that your brass model is made from nickel silver (which IIRC, is a type of brass alloy). 

[garethashenden]

Made two inner truck frames for the tender. Do to the split chassis design it's easier for me to have inside frames that carry the wheels and collect the current and the to have cosmetic outside frames.




And the tender sub-frame

[narrowminded]

Is your use of separate bushings instead of just reaming the nickle silver frame and using it as your axle bearing done for a particular reason?  Curious.

[garethashenden]

Is your use of separate bushings instead of just reaming the nickle silver frame and using it as your axle bearing done for a particular reason?  Curious.

They're wider, so there's a larger bearing surface. That's the main reason. Phosphor bronze is also a better bearing material than nickel silver.

[mmagliaro]

Excellent idea riding the axles in the frame and making the sideframes be just for show.
I've been debating with myself how I'm going to do this if I want to really gut it out and make my own sideframes.
Making them pure cosmetic is a lot easier than making them with precise cone holes for axle points!

This is nice work and very informative.  Keep it up!

[peteski]

They're wider, so there's a larger bearing surface. That's the main reason. Phosphor bronze is also a better bearing material than nickel silver.

Larger bearing surface means larger contact area between the axle and bearing. That means more friction (and if lubricated, more stiction).  The reason why the trucks with pointy axle ends riding in bearing cups roll so much freer than any trucks which use inside-bearing designs (even ones like the Kato Amfleet trucks).  This truck design will be wasting some of the loco's power.

[mmagliaro]

True (about the wasted power).  Pehaps a compromise could be had by using much thinner bearings.  It would never
be as low-friction as the axle-point cups, but it would be a lot better.  The main benefit I see here is being able to make
purely cosmetic sideframes that would not have to carry the wheels.  And that's a big benefit.

[garethashenden]

It's true that pointy axles roll the best. However, if you try to collect current through them they're far more prone to arcing. It is far easier to do it this way. There are many locomotive with tenders in this style, they seem to do fine. Technically, there is friction, but it's really not worth worrying about.

If the bearings are too narrow, they act more like a knife than a bearing and will make noticeable slots in the axles.

[peteski]

It's true that pointy axles roll the best. However, if you try to collect current through them they're far more prone to arcing. It is far easier to do it this way. There are many locomotive with tenders in this style, they seem to do fine. Technically, there is friction, but it's really not worth worrying about.

If the bearings are too narrow, they act more like a knife than a bearing and will make noticeable slots in the axles.

It is your model so, whatever works for you is what works the best.

Funny that the majority of model locomotives and most of the illuminated passenger cars utilize those needle-point axle pickups and we don't see people complaining about how unreliable that type of pickup is.  Why? because the pointy-axle design isn't that bad or prone to quickly getting dirty.

As far as thin bearings creating slots in the axles, I also have my doubts. Especially if the axle was steel and bearing phosphor-bronze.  Besides, as narrowminded has stated, the forces at play here are so small and the bearings (even thin ones) are way overbuilt that the last thing I woudl worry about is axle wear.

Looking as what you are doing here gives makes me better understanding of why model manufacturers sometimes come out with some really unusual designs for their models (not following what seems the best and proven practices).

[VonRyan]

It is your model so, whatever works for you is what works the best.

Funny that the majority of model locomotives and most of the illuminated passenger cars utilize those needle-point axle pickups and we don't see people complaining about how unreliable that type of pickup is.  Why? because the pointy-axle design isn't that bad or prone to quickly getting dirty.

As far as thin bearings creating slots in the axles, I also have my doubts. Especially if the axle was steel and bearing phosphor-bronze.  Besides, as narrowminded has stated, the forces at play here are so small and the bearings (even thin ones) are way overbuilt that the last thing I woudl worry about is axle wear.

Looking as what you are doing here gives makes me better understanding of why model manufacturers sometimes come out with some really unusual designs for their models (not following what seems the best and proven practices).

Remember Pete, Gareth is building his B15 using the tried and true methods of the English. Many outstanding 2mm scale locomotives have been built using the very same methods.

[peteski]

Remember Pete, Gareth is building his B15 using the tried and true methods of the English. Many outstanding 2mm scale locomotives have been built using the very same methods.

Sure, but there is always room for improvement.    Like I said earlier, it is Gareth's model - I am simply commenting on it (which I think is ok to do).

[randgust]

I think both are true.   I've seen arcing on end-axle pickups in the Kato 11-105 cups against the axle points, leading to erratic performance about the first 30 seconds if they've been sitting for a while, then they smooth right out as they reburnish themselves.   It's definitely related to weight, as well.  You don't notice it on most diesels because of the weight plus the heavier spring tension on the pickups.    Most times I think modelers blame wheel tread crud, but I became convinced there was something else going on as well.   I started to use Atlas Conductalube on the end-axle points on the Kato chassis and it pretty much solved the problem - that coating seems to prevent more arcing.  But it was at the end-axle points and cups.  Those are really easy to pop an axle out of and study with a magnifying glass, and yeah, there was some carbonization in there.

As far as for inside bearings, remember that every gearbox or steam chassis ever made depends on them.  It's all about the quality of the bearing material vs. the shaft material.   There may be more marginal friction, but good material and workmanship will eliminate a lot of it.

If I could find the right sideframes and wheelbase I'd opt for end-axles, but if I couldn't, well, the proof is in the end result.   I've certainly got the same problem trying to develop a Heisler.   Must have 8x8 power and 8x8 pickup.

When I did my HVRR 2-6-0 using the Atlas (Micro Ace) 2-6-0 chassis I also moved the motor into the tender so I had room for a 5.14:1 gearhead drive on the end of the motor.  If you get a gearhead in there, the increased starting torque of the drive will pretty much break loose the starting friction without hesitation; the 'sticktion' issue.    That project made me a real fan of tender drives and 8x8 pickup in tenders.  That is still the best small steam mechanism I've ever seen.