The MRR in the Attic - Blumentritt's Build Thread

[blumentritt]

The objective of this thread is to post the construction progress of The MRR in the Attic. Have in mind, that Rome wasn't built in a day. Thus, this is intended as a "long haul" thread.

Picture # 1: The largest furniture store on the planet just delivered the basis for Phase 1 of Blumentritt's Billiard Table.

 

[playmofire]

You must have strong rafters!

 

[blumentritt]

Pictures # 2, 3, 4, and 5: First "blocking rehearsal".

 

[blumentritt]

Pictures # 6, 7, and 8: Markings for blasting of tunnel with dynamite.







The width of the table is 60 cm.

The distance between the two tracks (center to center) is 18 cm.

The center of the radius is 8 cm above table top.

The radius is 20 cm.

Everything is aligned symmetrically to the center line of the table.

Tracks going in and coming out are straight, as is the tunnel.

My question to the experts: Will the tunnel be large enough or do I need to increase the radius? If not large enough, what would be the right radius? Any constructive comments are welcome.

 

[PhilP]

Looks a little tight?

Do you have (or intend to have) a caboose with a cupola?

(But I am no expert..)

PhilP

 

[Madman]

Perhaps a bit wider on the tunnel entrance. More live an oval. That is if you don't have room to go higher, as it appears a rafter might impede more height.

 

[JimmyB]

I would put the bottom of the circle at a hight of the top of the tracks, and run "vertical perpendicular lines (as tangents from the centre of the circle) down to the track base. Those that fully understand what I have written, will realise this is tautology.

 

[Greg Elmassian]

You could actually get the dimensions / clearance for the prototype, and scale to 1:20.3 for worst case.

Making it too tight can cause problems later.

See the "tunnel" below... you can see that I had to widen it several times. The point is not the particular car, but I needed to do better planning for all the cars I will run.

Greg

 

[JimmyB]

You could actually get the dimensions / clearance for the prototype, and scale to 1:20.3 for worst case.

Making it too tight can cause problems later.

See the "tunnel" below... you can see that I had to widen it several times. The point is not the particular car, but I needed to do better planning for all the cars I will run.

Greg

Greg, no disrespect, but it is pleasing to see it can happen to any of us, especially without planning all eventualities

 

[Greg Elmassian]

Yep, I don't mind airing my dirty laundry to help someone avoid the mistakes I made.

Also, the first iteration of that "tunnel" did not clear the smokestack on a 1:20.3 Shay... I was looking for pictures of my "clearance car"... I have an Aristo RDC that swings wider than any other piece of rolling stock, and the paint knocked off the end is a reminder to me ha ha!

Another item worth mentioning is don't assume a 4 foot diameter circle takes 4 feet, it takes much more, the 4 feet is the centerline, not the outer edge of the rail or the ties, and you need clearance outside that.

Anyway, a little extra clearance NEVER hurts. I have another one: A friend had a layout work well for years, several parallel tracks in a tunnel... bought a new Bachmann loco, and it entered the tunnel with window shades, but exited without. He had squeezed the track centerlines way closer than prototype.

Greg

 

[Rhinochugger]

Pictures # 6, 7, and 8: Markings for blasting of tunnel with dynamite.

View attachment 294171

View attachment 294172

View attachment 294173

The width of the table is 60 cm.

The distance between the two tracks (center to center) is 18 cm.

The center of the radius is 8 cm above table top.

The radius is 20 cm.

Everything is aligned symmetrically to the center line of the table.

Tracks going in and coming out are straight, as is the tunnel.

My question to the experts: Will the tunnel be large enough or do I need to increase the radius? If not large enough, what would be the right radius? Any constructive comments are welcome.

Yep, so the big issue is whether the track is going to go straight through the hole

 

[Chris Vernell]

Looks a little tight?
Do you have (or intend to have) a caboose with a cupola?
(But I am no expert..)
PhilP

PhilP is correct. I had a caboose with a cupola ... at least, it had a cupola until I ran it under a bridge

 

[Andrew_au]

Some other gotchas I've noticed wending my train tracks around porch supports:

• Just because the train goes into the tunnel straight doesn't mean you won't have overhang issues if it turns soon after. Particularly, when the track turns left, the back of the cars will stick out to the right.
• Parallel tracks are all very well until you have a corner. Between the standard overhang of the outer track and the reverse over hang from the inner, you can need a lot of clearance.
• Test your clearances at full speed. Faster trains sway more than slower trains, and this can transform an apparently safe corner into an expensive accident.
• Test your clearances with something that can handle being knocked. My LGB 49700 tanker cars have little drain pipes that stick out sideways in the middle. I was pleased to discover the other day that they are clipped on (rather than being part of the core plastic cast) when I had a clearance fail while testing.

(The tanker cars are good / horrible for testing clearances - they have an artificially wide middle and extra ladders that stick out at each end. Despite this, they'll happily handle even R1 curves as long as I leave enough clearance.)

 

[Paul M]

The bigger the better, within reason, you can always reduce the size of the entrances with a tunnel portal. I don't want appear silly, but have you checked that cutting a hole won't affect the integrity of the roof

 

[Rhinochugger]

Some other gotchas I've noticed wending my train tracks around porch supports:

• Just because the train goes into the tunnel straight doesn't mean you won't have overhang issues if it turns soon after. Particularly, when the track turns left, the back of the cars will stick out to the right.
• Parallel tracks are all very well until you have a corner. Between the standard overhang of the outer track and the reverse over hang from the inner, you can need a lot of clearance.
• Test your clearances at full speed. Faster trains sway more than slower trains, and this can transform an apparently safe corner into an expensive accident.
• Test your clearances with something that can handle being knocked. My LGB 49700 tanker cars have little drain pipes that stick out sideways in the middle. I was pleased to discover the other day that they are clipped on (rather than being part of the core plastic cast) when I had a clearance fail while testing.

(The tanker cars are good / horrible for testing clearances - they have an artificially wide middle and extra ladders that stick out at each end. Despite this, they'll happily handle even R1 curves as long as I leave enough clearance.)

Yes, on my first garden railway in Sussex, my Bachmann Connie could only approach the warren girder truss bridge from one direction - the curve on approach from the other direction caused and the overhang of the pilot caused problems.

 

[blumentritt]

Pictures # 9, 10, and 11: More markings.







Btw, the "tunnel" goes through a dry wall. Thickness around 10 cm. And before and after the tunnel on each side there will be straights for at least 4 m.

 

[korm kormsen]

i don't think, that a circle is the optimal shape for a tunnelportal.
try to think about an upright oval, or a square with rounded corners.

http://kormsen.info/landscape/bilder/lonemountain63.JPG

http://kormsen.info/landscape/bilder/lonemountain01.JPG

 

[viaEstrecha]

This is my double track portal, leading into a short, straight tunnel going under a footpath It is rigid foam, Noch product number 67360 [Noch website].

 

[Paul M]

Have a look at real tunnels, they tend to be the shape of ViaEstrecha's above. Probably for strength

 

[Rhinochugger]

Have a look at real tunnels, they tend to be the shape of ViaEstrecha's above. Probably for strength

There's most likely a trade-off between strength and economy - no point blasting rock away for the sake of it.

However, in terms of pure shape, while not a tunnel as such, I refer the honourable gentleman to Brunel's bridge at Maidenhead