Mmm... This has reminded me that I have a part built 70' Cowans Sheldon version in my shelf queens (not that it would fit on a shelf of course.....Bought from Dave Smith when he was trading as Metalsmiths. I haven't got any sort of motorising kit so I will be interested in what others are using.
Hi Rob, Keep an eye open as his nibs may do a blow by blow instruction. Could be amusing ...... Er...... I mean interesting. the dark side beckons once again. Do you have your deck made up as yet? Toto
Ok Gents a few questions 1. What is the turntable shaft diameter, and how far does it protrude below the base ? 2. What is the length of the turntable deck ? 3. How deep is the well ? 4. What is the external diameter of the well ? Here's why - Based on a 70ft turntable Deck (diameter) = 70 x 7 = 490mm Circumference = 3.142 x 490 = 1540 mm Nema 17 stepper motor 1.8 degrees per step = 200 steps per rev. Direct drive (motor connected to turntable shaft) with no gear reduction Each full step would move 1540/200 = 7.7mm Half stepping would move 3.85mm Quarter stepping would move 1.92mm 16th stepping would move 0.48mm This only gives us approx 1/2 rail width resolution. Thinking of something like the belt drives on record turntables, using a 3D printed 120T GT2 gear on the turntable shaft, and a 20T GT2 gear on the motor connected with a GT2 toothed belt. This gives a 6:1 reduction, so applied above would give (7.7/6) Full Step 1.3mm Half step 0.65mm Quarter step 0.32mm 16th step 0.08mm Depending on the gear box Toto has purchased (I'll assume 5:1 - until he tells me otherwise) ((7.7/6)/5) - giving a total of 30:1 reduction Full Step 0.26mm Half step 0.13mm Quarter step 0.07mm 16th step 0.02mm Measuring a piece of O gauge rail the width is approx 1.6mm wide, giving approx 6 full steps to cover the rail width. Why full steps ?, when 1/16th stepping direct drive would take 3 steps to cover the rail width and the tolerances would cope with the small misalignment. If you rotate a stepper motor you feel it notching from full step position to the next full step position, and providing no turning force is applied to shaft it will hold its position. Micro-stepping works by energising two coils to hold the motor between positions. As the turntable will spend long periods of time stationary, the coils will need to be permanently energised to maintain the position - which is going to get hot - very hot. By using the Full step, once the move is completed the motor coils can be de-energised. The gear box solution also will increase the torque available to move the turntable. Paul
Toto wrote: Hi Toto, By deck do you mean the bridge? if so yes, almost. This is as far as I have got, I haven't done anything with the base/well.
Wow Paul, that is a comprehensive reply, With regard to your questions the only measurement that I can recall is the the square base that the well sits in is 600 x 600mm. I would need to dig out the other bits to measure them.
Oh man ..... You have made a great job of the bridge. Very neat. If I remember correctly it also comes with timber sleepers. May be wrong there. I'll need to check my own. I have bought more of the brass stanchions which I thought about using around the outside of the turntable well. Just leaving gaps at each of the track openings. It will depend how many entry / exits I end up having. Just a thought ....... Might not happen. Cheers Toto
Toto wrote: Thanks Toto, It is a nice kit to build although there are a lot of rivets to punch out for the framing. I do recall making an error in that I cut the slot for the operating lever in the wrong place. The error will be covered by the planking (it is supplied) I have stained mine with Rustins dark oak stain and I haven't got as far as fitting it yet (I have cut all the pieces to fit so I have that jigsaw to work out again when I get back to it.
I've used Teak stain for sleepers to give that slightly faded effect on timber, and then rub talc or plaster into the grain again to flatten it a bit more. Paul
My Stepper motor and gear box arrived yesterday. Finally got it today as it was left with the neighbour. Anyway, I'll post a picture or two later. Cheers Toto
I have been talking to Dundee again about this kit ( I have another thread showing kit parts that I will maybe use for the build ) We are talking about DCC or not to DCC. I would prefer the turntable to be operated limited fashion. I'd like separate buttons to press to control each track address. I like to retain the DCC element for control of the locos rather than the accessories as I feel it's too much faffing around with handsets whilst you are try to control locos with it at the same time. ...... just my opinion, some folks are happy enough to do that. Fine . Another reason is that if it is an exhibition layout, Dundee and I always operate from the front and I'd like to let folks have the opportunity to operate the turntable without giving up the handset. And another reason .... .... is my experience with operating the previous traverses is that they were not always the most reliable. If they played up, Dundee had to be the one to be diverted off to fix it because it would inevitably mean computer aided jiggery pockery. Though excellent in theory and in practice when they behaved I feel they took too much time to nurse along at times. Dundee assures me he has sorted the solution to this but if I can get good old fashioned DC with accurate alignment of each road ..... I'd prefer that. Given that this turntable looks like its going to be used on a engine shed layout and the main running will simply be turning engines which may run off layout into a hidden siding etc, the turntable has to be reliable or it brings the whole layout , and any running capability to a complete halt. I dont have my head around the " control electronics element " yet so it may still use sardines or big easy drivers but wont be controlled from the handset. I'm looking at the build of the turntable as well and whilst looking through this thread saw Rob Pulhams " deck " build. I think the soldering looks easier than say that of a loco build soldering task. What's your view Rob and just how easy or difficult was it. I'll be off to the shed shortly to dig out the destructions again for a review. Cheers Toto
Thanks Rob, I guessed as much but sometimes my little naive mind can let me down badly. I was speaking to Dundee today and said I'd like to kick this off in tandem with finishing my loco build and before starting any more loco kits. We are discussing another start at an exhibition layout which shall be an engine shed layout but before building baseboards, we really need the turntable and shed built yo assist with the tra k geometry. It also kicks off other projects like the electrical / control elements. Anyway .... the instructions are out fir a read. Cheers Toto
And now I'm worried " Here we go again, off down the road again ..........." And here was me thinking he'd forgotten about this ...... Paul