Opinions please...

[emjaybee]

I have a 2' x 3' test loop at present.

I'm considering upgrading it into a more interesting affair.

I'd very much like peoples opinions on the proposal below. The track height where it crosses is 60mm above the lower one. I know the gradients are steeper than some would like, I think about 3%-3.5%, but for a test loop that's acceptable for me.

[TrevL]

Looks fine to me,  I would say you could get away with not having as much as 60mm between track heights.  I'm running  very successfully with 33mm clearance between top of the lower track and the overhead, with 43mm between track to track.  Admittedly I have a girder bridge, not a tunnel.

[jpendle]

In my opinion you've gone from a test track to an assault course.

I'd be wary of running in any loco on a gradient.

And your gradients will be on curves which makes them even tougher for a loco going up hauling a train.

As @TrevL says you don't need 60mm clearance, 43mm should be more than adequate.

Regards,

John P

[Merrylee]

Why don't you make it more interesting and make one go minus level and one go plus level and meet the bridge half way.

Ron

[Newportnobby]

As has been said, 60mm is over generous although none of my stock has pantographs.
My code 55 track sits on 1½mm thick underlay and nominal 2" timber (now 44mm) was fine from baseboard surface to base of the upper level baseboard.

[emjaybee]

Thanks all.

I set the 'height' of the rail at 60mm on AnyRail, so I'm assuming that it'd be rail top to rail top, which I've assumed will NOT take into account the sleepers, base, etc..

I did think about the lowering one and raising the other, which is what I have planned for my main layout in the future (not sure if I'll live long enough to ever get there mind), but my brain was struggling to comprehend the workings of that on this small plan, clear as a day in principle on my main plan, clear as mud on this!

In a previous thread I'd documented that I can get a BachFar Jubilee and a rake of eight Staniers up and round a 10" curve on a 3.5% incline with a small amount of slip, which is way more than I'd ever do.

@jpendle I hadn't considered the running in aspect. Has anyone else got any thoughts on that ?

[Newportnobby]

It's my belief all locos should be run in without a load but I think nowhere does it state "Thou shalt not use gradients, curved or otherwise"
I do agree with John, though, and would avoid doing that. Either just use a flat oval of track or a rolling road.

[Malc]

I had my flyover at 45mm, but had to jack it up a bit after it removed the air horns from a US EMD DD40 AX.

[maridunian]

I'd keep the upper level as low as running your biggest loco under it will allow, but make sure you can recover/restart any failures in the tunnel. My layout has separate upper and lower loops. The latter is pretty much flat so continuous steady running is possible on that. The outer is all up-and-down, but only ~2" in ~3' (1/18) on the steeper slope and 2" in ~6' (1/36) the other way.

Mike

[ntpntpntp]

I like to use a Unitrack K3 set for running in, it's a figure 8 set so loco bogies get to turn both ways, and there's a bit of gradient to apply a light load and bed things in.  I think the bridge piers give a clearance of 50mm

[emjaybee]

A minor update to this, I've finalised a track plan.





I've managed to squeeze in a headshunt. Following feedback on the crossover clearance I've got it down to 45mm, and the the internal loop gradient is going to be approx 2.8% whilst the outer loop gradient comes in at about 2.25%

The baseboard is well under construction as we 'speak'.

[AlexanderJesse]

Looks better and the grades should be doable by standard rolling stuff

[Lawrence]

Who says you can't have inclines on a curve 
Exhibit 1. my old B&O layout, admittedly I don't recall the height but it was way more then I needed for my track passing underneath and my EMD E8/9 would haul a rake of heavyweight coaches up there no problem.


In fact the gradient was even steeper at the other end and where they crossed I had enough room for a HiCube box car plus over a cm clearance, bad planing!

[emjaybee]

Following a rootle through my timber store, progress has progressed!

Please excuse the patchwork nature of the construction, I've used what I've got!




I'm planning on sticking the track down with Copydex, and I think I need to prime the wood first t assist with adhesion, am I correct?

What do people suggest for priming?

Do I use thinned PVA glue or paint the entire board with primer?

Suggestions please.

[ntpntpntp]

I've never bothered with priming the ply. I wouldn't have thought it necessary to prime for Copydex to stick - in fact probably stick better to the raw wood.   

I use cork strip for a track bed, it sticks fins to the ply with PVA.