Depends on at least two things- the track height and your flexibility. I'm not trying to be a smartaleck, but as we age, it gets harder to bend. And I hve found that duckunders just aren't as much fun as they used to be.
If built right, a swing-up (or down) section will work well. Either way, attention must be made to track alignment and a kill switch to electrically deaden that section of track so trains won't make that big drop to the floor, should the track be out of position.
I have a hinged bridge on my layout. I use a utility clamp to hold the open end in place. So far it's worked fine.
It has withstood a winter in the elements. I just used it yesterday with no derailments. The design is very basic. Just make sure the axis of the hinges is higher than rail head.
Keep yer countin' to your own damn rivets!
Always make a duckunder your last option. Try the other methods first. It is easy enough to make it solid later, if necessary.
I would use a lift up....But if you wanted to get creative, use a double lift up like a drawbridge, each half opening up. At 3 ft, each side would only be 18 inches. I know they make gurder bridges that length, I saw ono ebay the other day.
Hmmmm The bench will have 2" foam on it so I'll either have to swing it, maybe like a saloon door, not in both directions though, or raise some wood to the height of the foam to serve as an anchor for some hinges to flip up and make the sub roadbed there all wood. The double drawbridge seems like a good option as you pointed out only 18" on each side so there shouldn't be as much strain or the flex of a 3' section. I'll finish laying the foam and see what looks feasible. Thx for the input.
Flash Blackman has a cool swing bridge on his layout. It has buildings and all on it and just swings out of the way. When it is closed you really have to look close to see that it is really a bridge.
Russell Straw, Sugar Land Route
Get 2 of these. http://www.ebay.com/itm/330712751868...84.m1423.l2649 18"
this one is 21' it could swing back out of the way on the table about 3 in.
This is what I started to construct just today.
Two lengths of L-girder blocked between them with two lengths of pine 2X2, flanges oriented outward. At each lower corner, where this lift-out bridge of 27" is to be supported by a type of bracket shown at the far end, will be chromed steel L-brackets available in bulk at your hardware store. Around the head of one of the screws in the support on each corner will be wound a bared feeder wire connected close by to the main bus. Similarly, around one of the screw heads on the corner brackets on the lift-out bridge will be a bared feeder wire that will be threaded up to be soldered at the base of the rails crossing the bridge. When the sub-roadbed, roadbed, tracks, and ballasting are all in place atop the bridge deck, only then will I attempt to align the rails with the meeting rails at each end by placing the end support brackets in a suitable position and attitude, clamped, and then screw them securely into place. That should be all I ever have to do. The bridge is built like a brick outhouse, and those steel L-brackets should never wear out. If mounted properly, they'll also provide near-to-perfect alignment time and time again. And the gem is that they will constitute the only necessary electrical transmission switch to the rails when the bridge is in place, and only when the bridge is in place.
You're around my age, so, A duckunder is still workable, BUT . I'm a little over 6 ft tall I consider a reasonable duckunder to be at least 60 inches off of the floor. More like a nod under LOL . I wouldn't want to go much lower than that. If you're benchwork is a bit lower, then I would definately go with a lift out / hinged section.....Mike
Yea though I walk through the valley of the shadow of death I will fear no evil for thou art with me Thy rod and thy staff they comfort me