Author Topic: Scratched bridge shoe  (Read 4142 times)

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Lemosteam

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Scratched bridge shoe
« on: January 30, 2013, 07:24:28 PM »
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Anyone,  Before I make 5 more, is this a believable cast bridge shoe?  Still thinking about drilling and adding a pin...



From underneath:

« Last Edit: January 30, 2013, 07:44:07 PM by Lemosteam »

hegstad1

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Re: Scratched bridge shoe
« Reply #1 on: January 30, 2013, 07:27:47 PM »
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Looks nice!  If you're going to cast, add the pin!  You won't regret it.
Andrew Hegstad

davefoxx

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Re: Scratched bridge shoe
« Reply #2 on: January 30, 2013, 07:28:45 PM »
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I would probably add the pin, although I think I would also consider a small drop of CA that you could knock the top off of with a file to flatten.  Once painted and weathered, it should look really nice.  Bridge shoes are often ignored but really add that needed detailing.

In other words, it looks great to me.  I'll take eight, please.

DFF

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jimmo

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Re: Scratched bridge shoe
« Reply #3 on: January 30, 2013, 07:32:29 PM »
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Looks like a bridge shoe to me. It needs to be located all the way to the end to take advantage of the extra strength of the vertical rib close to the end of the girder.
James R. Will

Lemosteam

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Re: Scratched bridge shoe
« Reply #4 on: January 30, 2013, 07:43:15 PM »
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Thanks!  Actually I'm surprised one is not molded onto the girder bottom. The lower pieces could be on a sprue and snapped into the groove.

The two parts are loose right now.  Not that anybody asked but it was made with a 2.5mm Plastruct traingular rod.  I sanded the radius on one corner and then ground a clevis into the triangle on on the rounded edge.  The plates are .010" styrene, trimmed after gluing the traingular pieces on.  The shackle that fits in the clevis is just a shaving off the end of the rod.

If I pin them Ill let them pivot.  Max Magliaro found some miniature "bolts" for his running gear...  Hmmm.

It was easy enough to make I don't think I'll be casting them! 

Ohhhh David K Smith???   :D

Jimmo, ahh, but it is located where the cross beam meets the stringer...  Added another shot above^^
« Last Edit: January 30, 2013, 07:46:07 PM by Lemosteam »

jimmo

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Re: Scratched bridge shoe
« Reply #5 on: January 30, 2013, 07:51:21 PM »
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Jimmo, ahh, but it is located where the cross beam meets the stringer...  Added another shot above^^
[/quote]

That's actually less relevant than having them supporting the corner of the girder. Remember that the girder IS the major load-bearing part of the bridge and the stringers attach to it and are not directly supported by the shoe. Many modelers don't know this and support the bridge in all sorts of ways. It's the corners that carry the load of the bridge down through the shoes and into the abutment.
James R. Will

Bsklarski

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Re: Scratched bridge shoe
« Reply #6 on: January 30, 2013, 07:56:38 PM »
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A thin slice of stretched sprue would make a nice pin and save you all that time
Brian Sklarski
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Alwyn Cutmore

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Re: Scratched bridge shoe
« Reply #7 on: January 30, 2013, 08:35:37 PM »
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Hi John,

Mould them as two halves and mark a dimple on both sides to show where the pin hole is drilled through. Use lace making chrome plated pins for the pins as they had a head which can be used on the inside out of sight  as the pivot.

Regards

Al
Al Cutmore
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Lemosteam

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Re: Scratched bridge shoe
« Reply #8 on: January 30, 2013, 09:12:03 PM »
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Or a dab of solder ground to a hex on a 0.015" brass wire, and yes, it pivots  :P:



jimmo, I would have to respectfully disagree with you on the shoe placement.  Cantilevering all of the load out to the very corner beyond the structure would likely allow the center to deflect and try to rip the girder off.  Placing it here spreads the load to all the members, not just the girder.  All of the load bearing including the ribs on the inside of the girder come down to that structural intersection below. 

I have observed these shoes set back from the end of the bridge.  An image showing otherwise would help!

peteski

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Re: Scratched bridge shoe
« Reply #9 on: January 30, 2013, 09:13:22 PM »
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Remember to model the sliding shoe on the opposite end of the bridge. It needs be able to contract and expand with temperature!  :D
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Lemosteam

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Re: Scratched bridge shoe
« Reply #10 on: January 30, 2013, 09:18:46 PM »
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peteski, what would that look like?  An elongated version of this with a slot for the bolt to slide in?

Bsklarski

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Re: Scratched bridge shoe
« Reply #11 on: January 30, 2013, 09:31:24 PM »
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Nothing fancy, usually sometimes just square steel shapes.



Brian Sklarski
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pnolan48

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Re: Scratched bridge shoe
« Reply #12 on: January 30, 2013, 09:36:44 PM »
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Sometimes the sliding shoe just sits on another steel plate. On larger bridges, the sliding shoe has rollers that slide on the steel plate.

Lemosteam

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Re: Scratched bridge shoe
« Reply #13 on: January 30, 2013, 09:43:39 PM »
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Cool.  Now I only have to make four of these!!! :D :D

Thanks Brian for the pics.  I assume the slider is the block under the shallower bridge (I can see a gap between the two) and the pivot is below under the deeper bridge?

peteski

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Re: Scratched bridge shoe
« Reply #14 on: January 30, 2013, 09:46:04 PM »
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peteski, what would that look like?  An elongated version of this with a slot for the bolt to slide in?

There are many types of bridge bearings.  I suppose the one you made could also be a sliding bearing if there was a sliding plate on the bottom of yours (instead of being bolted down to the pier).  The ones I've seen have a curved surface that rests on a flat plate. This allows it to move.

Here is kind of an odd example (best I could find):


They could also be made of neoprene (which flexes);


--- Peteski de Snarkski

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