Can I suggest contacting Central Valley for advice?
https://hosting.photobucket.com/albums/yy132/HOn30critter/Signals/.highres/DSC02637_zpsz4n2lk8z.jpg?width=301&height=183&fit=bounds&crop=fill
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
JohnWPowellWow well i wonder what I did or didn't do
Let's try to diagnose this. You said earlier the steel reinforcements were installed. There are other places to check for structural issues:
Rob Spangler
I should have also mentioned that the truss portion of the bridge likely adds little in the way of strength, as it's not cemented to the bridge's deck, but merely snapped in place, as an aid for track cleaning (which is seldom required).
The entire five-span bridge (four deck girder bridges and the truss) are also removeable from their piers and abutments as a single unit...good for those times when the "water" needs to be cleaned.
Wayne
I thought I built them just like he did in the YouTube videos. Im not sure what is going on. Thank you
Wow well i wonder what I did or didn't do
While I no longer own the three 33oz. U-boats, here's the Central Valley truss bridge with two machinist's steel blocks, not quite on the centre of the same bridge....
Total weight (and concentrated, rather than distributed like the just-over 6lbs of the three U-boats) is 7 pounds.
The measured deflection of the bridge's bottom-member was 3"(HO).
I am eyeballing a P2K SD50/SD60 pair crossing my CV truss bridge. I see, against the background, some very small flex. I'd say about 1/16", not 1/8". The locos weigh about 26 oz. each. How much does yours flex downward with 2 locos atop?
Paul
Modeling HO with a transition era UP bent
I have built the HO scale Central Valley Pratt Truss Bridge, and never had a problem. The model is very rigid.
How heavy are these locomotives?
-Kevin
Living the dream.
The CV truss bridges have metal reinforcements, plus connections between the crossmenbers below the track and the actual truss assembly. Both work together to keep the structures straight when there's weight on them. If they're deflecting sufficiently that locos come uncoupled, it seems likely to me they weren't built according to the directions, or there's weakness in the assembly from parts that aren't secure.
Yeah, with the steel reinforcing plates installed in the bottom members of the span, there shouldn't be any noticeable deflection. I've run my three modified Athearn U-boats (33oz. each) over my Central Valley bridge without any noticeable deflection of the span.
A plier is a a pier that lies at the juction of the two bridges.
My assumption is the flexing is going on at the center of each span since there is a pier. There are lots of CV truss bridges in the forum and this is the first I've heard of the problem.
Henry
COB Potomac & Northern
Shenandoah Valley
Hello All,
JohnWPowellYes they are ho and the steel reinforcements are installed
What "steel reinforcements" are you referring to?
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
JohnWPowellYes there a plier between them
Can you describe what a "plier" is?
Yes they are ho and the steel reinforcements are installed
JohnWPowellI have 2 cv truss bridges together when a train goes over them the bridge flexes so much motors uncouple from each other. What's a good way to fix this?
All of these questions need consideration even in model railroading.
If you can answer these questions the great folks on these forums can help you better.
Yes there a plier between them
Is their a pier in the middle?
I'd try putting some beams along the bottom near the edge on each side and disguise them as something like a pipe or some kind of decorative fairing.
Assuming HO and assuming you fit the steel reinforcements you can reinforce the main parts underneath with metal box tube or wood though the box tube would be easier to hide. Both structures deflect? I have one of the 150ft versions and I haven't had that happen yet. Let us know how you progress. J.R.
Easiest way is likely to be to make up rigid reinforcing beams and cement the upper flange as continuously as possible to the underside of the bridge, either on the centerline if double track or under each track center. You could design slight camber into this as preload against sag if you want to keep the beam section down for visual reasons. If visibility is a concern you can use Plexiglas or similar optically-clear material for the web.
i'd recommend against trying to make fancy modeled lattice trusses for these beams -- that sort of fabrication at "HO scale") will seldom have the necessary strength and rigidity for long-term effectiveness; this has been proven time and again at 'engineering challenge' competitions.
Ed will be able to provide you with a number of pictures of prototype bridges (e.g. perhaps in the P&LE) where truss bridges were strengthened for heavier service instead of being replaced. Some of those might work in your situation...
I have 2 cv truss bridges together when a train goes over them the bridge flexes so much motors uncouple from each other. What's a good way to fix this?