Wardell Bridge

Peter

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#21
It was time to put in the roads, but first I had to make the traffic lights, and install the wiring. I could not find LED traffic lights of similar size to the ones I used on the span. So I had to make my own. I used a strip of wood which looked and behaved similar to bamboo. My first few attempts to drill the holes for the LEDs failed. Then I found the correct way to go about it. The sides of the light box is from card. This not only keeps the box thin in appearance but also easy to access if future repairs are needed. The LEDs used are 5 mm in diametre. Bottom right photo only shows how it would look on the bridge.

44_ Traffic Lights.jpg
 

Peter

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#22
Before assembling the towers into place, I realized that the span would not be able to be removed for any repairs. Both the bumper rollers and the pulley wheel overhang restricts removal. So I decided to replace two of the lateral bumper rollers with a detachable design. Now the the span can be removed laterally (sideways).

45_Bumper Rollers Modification.jpg

Here I am building the road and footpath surfaces. I used 3 mm Masonite. There are about 280 holes drilled to railing posts.
The traffic lights were installed. All the bridge wiring had to be routed along the girders and down through the table top. The road surface also had holes and square sections cut out to accommodate the travel of the pulley cables, gate servo axles, and anchoring of the towers.
46_Bridge road.jpg

Now it was time for installing the railings. Over 35 split skewers, for railings, were needed. Each matchstick was squared level to the table and not to the curvature of the road. Four days later I got it all done. The gaps you see, near the traffic lights, are for the swing gates. I am still waiting for some brass tubing to arrive.

Where I live, Ballina and nearby towns, all the hobby shops have closed down. To get brass tubing and the like, I have to use the Internet to purchase from overseas. It can take over a month to get some things.
47_Bridge road railings.jpg
 

Peter

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#23
At last, my last post to where I am at at the moment.

Here I tipped up the table to access the bottom of the display. I gave it an undercoat of acrylic paint.
The white cards you see are placed over the holes for the fender piers. So when I install them they will all be at the same height.

Terminal strips were put in place to terminate all the wires that came through the table. Then I made several flat brackets, painted them white, and used them to flatten the wiring harness. This makes following the wires much easier. The wire ends will eventually go into the (under the table) control box.
48_Display Table Wiring.jpg

This is where I am at now. Thank you so much for your patience and persistence to read up to this point.
I will update my progress about 1-2 times per week.
 
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John
#24
Wow! Impressive project, and looks like it's going to look amazing in situ. Good work indeed!
 

Snowman

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#25
Simply amazing!! :confused::eek::cool::cool:
What a project!!:confused::eek::cool::cool:
 

grumpa

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#26
This goes far beyond just model building, engineering , mechanical, electrical....it's all there...BRAVO!.....Jim:smiling3:
 

monica

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#28
amazing work,Peter,Impressive project,loving your detail,and work,;)
 

Peter

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#30
Wow, what a lot of 'pats on the back'.
Thank you John, Gavin, Jim, Ian, Monica, and Steve.

To tell you the truth, I am apprehensive yet confident at the same time. But simply, my goal is to make it work; and to work for a long time.

Part of my apprehension comes from when I was a teenager who wanted to build a moving sculpture. I remember becoming crestfallen when I read from a famous artist 'that a sculpture should not be made to move'. The reason was that if it stops moving its purpose ceases, and if it cannot be repaired it becomes useless. Then many years later I heard a counter quote from an artist who said 'that a piece of art is not complete if it cannot stand on its own'. The reason was that it should not have to rely on a frame, on a light setting, or movement, etc.

The other part, is my confidence. This simply comes from a belief I picked up from a Star Trek episode. "Nothing is impossible. It only seems impossible because we don't yet understand how it could be possible". Or something along those lines. So the word 'impossible' is not in my vocabulary. So when somebody says it is too difficult, or impossible, I suddenly think I am talking to a stranger.

However, I have also learnt to not worry about the results. Focus on the process and the results will take care of itself.

I am hoping to create an interesting diorama so that the display can stand on its own (without power to it). This is where I know I will be relying heavily on the forum members. I am hoping you will be able to give me advice and suggestions when it comes to the landscaping, etc. you all have the experience, where I don't. However I have to warn you, I can be stubborn in my ways, so please don't get upset if I don't follow somebodies suggestions.

Thank you for your support.
 

Peter

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#31
I may have solved a problem with using servo motors for opening and closing the bridge gates. I never used servos before, but their data sheets say they can rotate fairly quickly. Too quick for my liking. If I used the servos as is, the gates would swing 90 in a very snappy way. My options are limited to what the museum budget allows. So to use reduction gearing requires delicate gearbox housing construction. And the slowest servos are used with model sailing boats, and they cost a fair bit.

Normally, to vary the speed of a DC motor, the voltage supplied to the motor is chopped (pulsed). Pulse-Width Modulation (PWM) is used. However, servo motors use PWM for servo arm positioning. So PWM cannot be used, as well, for speed control.

While designing a lever system for operating the gates I saw a way around my problem. The gate has to swing 90 deg, and the standard servo rotates 180 deg. Using different length drive arms for servo and gate axle, a change of speed, or more correctly 'time', can be accomplished. The time for the servo to travel 180 deg can be the same for a gate travelling 90 deg. That is half the speed (though not at a regular pace [deg per millisecond]).

This is my plan. (please note, sometimes my plans don't work out).
180 to 90 reduction in speed.png
 
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#32
I knew that, " what did he say " lol.
Outstanding build Peter way over my head mate, looking forward to the next installment.

John
 

Ian M

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#35
Looking very nice. I do though have a question that stems form my ignorance.
The way my mind works, a big gear on the motor and a smaller gear on the wheel normally makes the wheel go faster with less torque. (thinking bicycle wheels here).
Surly this would mean to get the faster servo to lift the 'heavy' bridge you would need a small gear on the servo and a large one on the bridge section.
But these are just my thoughts, so probably way off the target. lol
Would a small motor and a couple of mini switches not do the job?
 

Snowman

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#36
A reduction gearing is the best option if you are using a fast motor - small drive gear (pinion drive) to large driven gear. If a slow, high torque motor is used then no reduction should be required unless only for scaling.
 

Peter

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#37
Hi Ian.
To clarify, the servo is only for the swing gates. These gates will be located in those gaps you see, near the traffic lights, in the above photograph. The servos are positional type and will be set to only turn 90 deg.

You are right about using a small gear on the servo motor, to drive a larger gear for slower revolutions and greater torque. But to do this requires reasonable accurate assemble of a gear box (even for one gear). My thinking is to simply use a lever system as described in post # 31.

The bridge motor is a standard DC motor with a 148:1 gear box ratio. The output shaft rotates at o.77 r.p.sec (1 rev per 1.3 seconds) . Bridge span speed will mainly depend on the drive pulley diameter, which winds the cable in and out. If this is still too fast, I will simply put a DC motor speed controller on the motor, and set it for the desired rate of span lift.

Has my explanation helped? If not please feel free to ask any question or give any suggestion for consideration. I welcome any thoughts and feedback.
 
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Peter

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#38
A reduction gearing is the best option if you are using a fast motor - small drive gear (pinion drive) to large driven gear. If a slow, high torque motor is used then no reduction should be required unless only for scaling.
Thanks Snowman. Your quote is true, and just beat me to the post.
 

kpnuts

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#40
Wow I'm gobsmacked, that is an epic and awesome build, and all this technical talk just flies right over my head.
Amazing.
 
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