Drawbridge build attempt

[Madman]

I'm planning to build a drawbridge for my railway. I've been experimenting with some designs and think I may have stumbled upon a simple one. I like simple. Has anyone else built a working drawbridge for their railway?

 

[tramcar trev]

No I haven't built one... BUT I will follow your progress as I need a 3 metre long bridge that can be lifted over my drive and I have to be able to have a trolley wire on mine....

 

[viaEstrecha]

I did mine relatively simply by using a brass hinge kit for an LGB 1200mm bridge, so that I can swing it up and out of the way to access a cutting and prune the rose on my back fence. It has been quite successful. Although I use the sprung ball bearing rail connectors at the opening end, I put additional power connectors into the bridge track, just in case. I also added two strips of galvanised steel along each side to give extra rigidity.

The bridge is now in a different location - this was its first site, across a path:

This is of course entirely manual - were you thinking of something clever and powered?

 

[bobg]

I have a bridge section to allow mower access. As I see it, the main criteria for determining construction of any bridge has to be its height above ground, by its length. Mine runs from around 3" to about 10" and as it happens runs uphill from the high end to the low end. Mine is about 7` 6" long, and has support over most of its length, easy, because its low.

I don`t leave it in place but store it vertically in the garage. Steam requires no leccy connections of course, but I use `slackened` fishplates, slid over each rail to maintain alignment, whilst the main section has wooden guides at each end. 



One minor drawback is the need to mow before fitting the bridge. Not absolutely essential but it eases fitting.

 

[Rhinochugger]

Go to the back of the class - that garden's much too tidy

 

[bobg]

Go to the back of the class - that garden's much too tidy

That's coz it's only grass!

 

[PhilP]

My grass doesn't look that tidy..

 

[bobg]

Yeah but it's on'y jus' been cut, anerit! : :

 

[tramcar trev]

My grass never needs cutting....When we bought the house it was owned by a chap of middle European origins and he had concreted the whole lot, he didn't want anyone bombingk his house..... We got shot of it after a while and had a very realistic fake lawn installed, we even have weeds growing in it...

 

[Madman]

I`ve been making some progress on the bridge.  Yesterday I built, what I thought I wanted, from wood.  Today, after a good nights sleep, I came up with what I think will be much more workable and durable.  The only issue left is the pivot point.  It may be that I placed the hinge incorrectly, but I may have a solution.  I`ll go into that on Friday, as tomorrow is turkey day.  But for now I do have some photos to show.  I don`t have a photo with the hinge mounted.  that will come in my next post.

 

[trammayo]

Looks quite substantial - guess you're going to need a 'substantial' counterweight!

 

[tramcar trev]

Looks like Dorman Long built that...... I saw Obama give a reprieve to a turkey today on the news....

 

[Tim Brien]

Dan,
I presume that the hinge point will be where the bridge intersects with the support structure. Thus the hinge centreline will need to be about 1 cm (0.5") or more above the rail height. This will allow the bridge to lift clear of the adjacent track without interfering with it, allowing a minimal gap between the bridge mounted track and the structure mounted track.

Edit: a friend built a massive drawbridge approximately two metres in length and used an inexpensive 12 volt Chinese boat trailer winch to raise/lower the deck.

 

[tramcar trev]

Dan,
I presume that the hinge point will be where the bridge intersects with the support structure. Thus the hinge centreline will need to be about 1 cm (0.5") or more above the rail height. This will allow the bridge to lift clear of the adjacent track without interfering with it, allowing a minimal gap between the bridge mounted track and the structure mounted track.

Edit: a friend built a massive drawbridge approximately two metres in length and used an inexpensive 12 volt Chinese boat trailer winch to raise/lower the deck.

All hinges and other "hardware" should be of brass or stainless steel to eliminate corrosion. Paint or weathered to render "invisible". There were 2 swing bridges on the Sydney tramway system, I'm researching them to try and find out what/how the trolley wire was dealt with. In a real life situation metal bridges and electric traction have very real corrosive problems due (they tell me) to eddy currents and dissimilar materials though I doubt that would be an issue with a few V dc....

 

[ge_rik]

All hinges and other "hardware" should be of brass or stainless steel to eliminate corrosion.

Be careful with hinges which appear to be brass - I bought a couple to hinge my bridges without realising that while the flaps of the hinges were brass, the pivot pins were steel - they lasted about six years in my damp NW England garden before the pivots gave up

Rik

 

[PhilP]

See the earlier examples..
You do need the pivot-point of the hinge well above the deck / rail height.. This means the bridge superstructure does not foul as it pivots, and allows the far end to 'drop' nicely into place.

If not steel hinge-pins, then what material??
How rust-proof is stainless steel? Would bronze be an option?

 

[tramcar trev]

See the earlier examples..
You do need the pivot-point of the hinge well above the deck / rail height.. This means the bridge superstructure does not foul as it pivots, and allows the far end to 'drop' nicely into place.

If not steel hinge-pins, then what material??
How rust-proof is stainless steel? Would bronze be an option?

stainless steel is fairly corrosion resistant, if you can find bronze hinges let me know... You can buy loose pin brass hinges so that the pin can be pulled completely...
http://www.ebay.com.au/itm/Quality-Door-Butt-Hinge-SSH70-L-70x50x1-6mm-Loose-Pin-Stainless-Steel-/271278305073?pt=AU_Building_Materials&hash=item3f29726f31

 

[Madman]

Dan,
I presume that the hinge point will be where the bridge intersects with the support structure. Thus the hinge centreline will need to be about 1 cm (0.5") or more above the rail height. This will allow the bridge to lift clear of the adjacent track without interfering with it, allowing a minimal gap between the bridge mounted track and the structure mounted track.

Edit: a friend built a massive drawbridge approximately two metres in length and used an inexpensive 12 volt Chinese boat trailer winch to raise/lower the deck.

I was thinking about the hinge point in my sleep last night. Being a carpenter, you would think that I would have thought of the hinge point first. You are correct, the pivot point does need to be above the rail top.

 

[Madman]

Looks like Dorman Long built that...... I saw Obama give a reprieve to a turkey today on the news....

Uh, I think that turkey is in my fridge at the moment :

 

[PhilP]

Uh, I think that turkey is in my fridge at the moment :

?? You have Obama in your fridge ??