Crinan

[Signaller69]

Hi there Martyn.

Firstly let me say that your layout is so convincing that I spent about an hour on the interweb searching for images of the railway at Crinan. It wasn’t until I reread your thread from page 1 that I realised that it was freelance and that although there is a swing bridge there in real life it’s the one at Benavie that your bridge is based on.

Now then having read your description of the bridge and mechanism in your reply to my post I can see where you have gone awry with this. There are two problems with this and no matter how much you fettle the mechanism it will not run properly, it may run better but it will not fix the issue. The biggest problem is the point of balance and the fact that it is bearing on the pivot and not on a proper bearing. The pivot is providing a very small surface area and the two ball races you describe the pivot shaft running in are not doing what you think they are. They are not supporting the deck in any way; all they are doing is allowing the shaft run freely on its axis. The fact that the balance point is not exactly on the centre of the pivot is inducing a lateral force which is causing the pivot shaft to flex and is forcing the ball race into the side of the bearing cup and although the force isn’t very great it will cause what appears to be a tight spot in the drive chain.

The best analogy for this is the use of a worm and worm gear with grub screws in a loco drive. People will spend many hours building a loco chassis that runs like silk without a motor fitted and when they fit a motor to the gear box the chassis will run fine one way and be jerky the other or poorly in both directions they then spend hours and hours fettling the chassis again and again to try and fix the tight spot or running the motor back and forth to run it in when the problem is not caused by anything on the chassis or wheels or the coupling rods. The problem lies not in the parts they have fettled but with the fact that when the grub screws are tightened on the worm and worm gear they are both pushing the gears off centre because the hole in both of the gears are larger than the motor shaft and axle. The answer is to file a flat on the axle and motor shaft and only do up the screw until it just touches and add a spot of glue so it doesn’t move this will allow a little backlash but the tight spot will disappear.

Now to get the bridge to run properly you have to get the balance point in line with the centre of the pivot and give the bridge a proper bearing that actually takes the weight of the bridge. This is not a big problem and has two fairly simple solutions.

#1: add more weight to the short end of the bridge. Now I know you have run out of room for more weight but there is something you can do about it that you may not have thought of. The curved segment at the end of the deck next to the weight you have added can be made of metal could it not? Also there is space between the weights and the curved section that could be filled with “liquid lead” which will give you a few more grams that end. There is also space beneath the rails that have blobs of glue in at present that could also be treated the same way.

#2: reduce the weight at the long end of bridge. You can do this by using a dental burr or milling bit in a mini drill to gouge out some of the underside of the deck a bit at a time until you get the balance perfect without having to touch the top side of the deck.

There is a third option but it involves a partial rebuild of the bridge deck and it would give you lots of voids in which to install more weight that would be totally unseen.

Once you get the balance right you can install a tapered roller bearing around the pivot to take the weight of the bridge and you will have no weight on the pivot at all. Now as it happens I came across just the thing you need on fleebay with the following dimensions ID 25mm OD 47mm H 10mm for less than a tenner.

I hope that you find this useful.

With kind regards Lez.Z.

Wow, thanks Lez you have clearly given this a lot of thought! I hadn't considered flex in the main drive shaft as it is steel and it had worked very smoothely prior to mucking around with gear ratios but I do take your point, it is worth investigating and I will look again at the balance to see if I can get it spot on using the methods you suggest.

 

Thanks again,

Martyn.

[lezz01]

Hi Martyn. 

Yes you are right I have given it a lot of thought, some would say too much. I also totally over engineer things. I will be the first to admit the tapered roller bearing is complete overkill. The bearing I mentioned is the top steering yoke bearing for a KTM motor bike, In reality the disc on the underside of the bridge will be more than sufficient for the weight of the bridge. Just add a similar disc to the bridge plinth and lube it up and all will be well. The problem is just that you think have run out of places to add more weight. The easy answer is to remove the deck plating in the 4 foot and then you will have lots of space between the sleepers to add as much weight as you need to balance it all up. Whether you can do this without damage is the issue and what I was trying to avoid. I wish you luck with it as I'm sure you can find the solution that suits your way of working best.

Regards Lez.Z.       

[Signaller69]

Hi Martyn.

Yes you are right I have given it a lot of thought, some would say too much. I also totally over engineer things. I will be the first to admit the tapered roller bearing is complete overkill. The bearing I mentioned is the top steering yoke bearing for a KTM motor bike, In reality the disc on the underside of the bridge will be more than sufficient for the weight of the bridge. Just add a similar disc to the bridge plinth and lube it up and all will be well. The problem is just that you think have run out of places to add more weight. The easy answer is to remove the deck plating in the 4 foot and then you will have lots of space between the sleepers to add as much weight as you need to balance it all up. Whether you can do this without damage is the issue and what I was trying to avoid. I wish you luck with it as I'm sure you can find the solution that suits your way of working best.

Regards Lez.Z.

If removing the plating in the 4ft is too risky, I think I can probably remove the walkways either side of the track to add a little weight near the short end.

 

I do have a few spare ball bearings to try before buying any more so will see how I get on and update once I have experimented.

 

Cheers,

Martyn.

[luckymucklebackit]

Hi Martyn - don't know if you were watching TV last night but there was a programme on BBC4 about the Puffers featuring Crinan,  It could well be on iplayer

 

Jim

[Signaller69]

Hi Martyn - don't know if you were watching TV last night but there was a programme on BBC4 about the Puffers featuring Crinan,  It could well be on iplayer

 

Jim

Thanks Jim, I missed it unfortunately, but will look out for it thanks!

[Signaller69]

Bridge balancing sorted via a little more liquid lead and a couple of old Lima coach weights which should just about clear the base on which it sits; Not looking pretty at the moment, but some paint should disguise them as what they are - counter weights - any visibility would only be very slight and then only when the bridge is open to the canal. The plastic pivot tube served only as a guide for the drive shaft (no bearing capability) so this will be cut down to sit on the free part of one of the ball races seen resting on the underside of the deck, which will itself sit in the hole in the bridge base through which the drive shaft protrudes. Fingers crossed for testing then!

Before & after:

[Signaller69]

Well, after much messing around balancing the bridge deck and fitting an extra ball race to the drive shaft (see photo) and checking there is no catching / friction anywhere, unfortunately the slight bridge jerkiness has not subsided so it can only be the gear train causing the problem (it is a rhythmical jerking so still a gear tight spot I think). Still, it has narrowed down the possible causes. . .

[Regularity]

The swing bridge has been giving me headaches for some time. Although the mechanism seems to work ok, during opening and closing it tends to catch and be a little jerky.

 

Unless you spend a lot of money on very precisely made gears, and have an anti-backlash gearbox as your final drive, then some jerkiness is all but inevitable. But if you follow Lezz01’s suggestions, you can reduce that.

I put this down to 2 issues; firstly the weight is not balanced about the pivot point, mainly due to this being just over a quarter of the way along the deck. Although I have added a fair amount of weight at the short end it still wasn't enough. Not having any more space under the decking I opted to fill the rear girder sections with "liquid lead" shot secured with PVA. As these sections are plated over anyway this will not be visible once the new "plates" are added.

Argh. Get that out of there.

The PVA and the lead will react, producing lead acetate. During this process, the mixture will expand. It won’t be immediate, but the reaction has already started.

Use something like epoxy resin, Bostik clear adhesive or UHU instead. But as these are in an ecnclosed space, why not simply trap the lead shot with the panels? Or better still, cut some lead sheet to fit the aperture: there will be no interstitial gaps this way, and you will acquire a greater density and hence more mass in the space.

[Signaller69]

Unless you spend a lot of money on very precisely made gears, and have an anti-backlash gearbox as your final drive, then some jerkiness is all but inevitable. But if you follow Lezz01’s suggestions, you can reduce that.

Argh. Get that out of there.

The PVA and the lead will react, producing lead acetate. During this process, the mixture will expand. It won’t be immediate, but the reaction has already started.

Use something like epoxy resin, Bostik clear adhesive or UHU instead. But as these are in an ecnclosed space, why not simply trap the lead shot with the panels? Or better still, cut some lead sheet to fit the aperture: there will be no interstitial gaps this way, and you will acquire a greater density and hence more mass in the space.

Hmmmm, I will keep an eye out for expansion in that case, thanks for the warning. I do usually use epoxy resin for such jobs tbh.

 

The balance / extra bearing side is sorted ok so I'm going to investigate the gearbox when I find time.

[lezz01]

Hi Martyn.

I go with superglue for liquid lead myself it sets faster. As for the gear box remove from the layout use a little toothpaste on the gears and run at a slow to moderate speed in each direction for around 5 mins total wash it all out thoroughly then blow dry it till its completely dry lube up and give it a try. Repeat as necessary. DO NOT overdo this as it's easy to make it sloppy and once you've ground it away you can't put it back but you can always grind away a bit more. Toothpaste is very abrasive! Just a little repeated as many time as you need to is the best way to go. Do make sure you get all the muck off each time though and don't get it in the motor. If you don't fancy using toothpaste use liquid metal polish instead but do make sure you flush it all out and dry it properly every time. 

Regards Lez.Z.    

[Signaller69]

Hi Martyn.

I go with superglue for liquid lead myself it sets faster. As for the gear box remove from the layout use a little toothpaste on the gears and run at a slow to moderate speed in each direction for around 5 mins total wash it all out thoroughly then blow dry it till its completely dry lube up and give it a try. Repeat as necessary. DO NOT overdo this as it's easy to make it sloppy and once you've ground it away you can't put it back but you can always grind away a bit more. Toothpaste is very abrasive! Just a little repeated as many time as you need to is the best way to go. Do make sure you get all the muck off each time though and don't get it in the motor. If you don't fancy using toothpaste use liquid metal polish instead but do make sure you flush it all out and dry it properly every time.

Regards Lez.Z.

Thanks Lez for reminding me of the toothpaste trick, I have used it before on metal gears so will try it on this gearbox too. It is only one of the cheap "project" ones which has been modified with proper bushings fitted; from a quick look under the layout I have a suspicion one of the idler shafts isn't quite parallel to the other due possibly to the 2 halves of the shell not being aligned quite as they should so when I have a chance to remove it I will check, and then do as you suggest.

[Signaller69]

Another modification concerns the off scene sector plate, which has a folding (electrically dead) extension. A limitation with this was the 7 roads and that the maximum it could comfortably hold was a class 27 with 3 Mk.1 coaches plus a 57' BG/GUV. As I have made up a couple of new rakes of 4 x 64' coaches each this would have meant them overhanging the swinging end; I had thought of making a new longer folding extension but for now, extending the existing one by 2" has provided the answer. A 2" wide strip of spare 1/2" plywood was fitted and the pivot point on the fixed part of the sector plate will be moved 2" nearer the end to compensate. There is still enough length in the extension "arms" to allow it to be self supporting off the fixed part.

 

Fiddle yard in use before altering (join between folding extension and "fixed" sector plate is seen under the brake van behind the Clayton on the right):

 

2" Extension added to the folding extension and cork sheet cut to size ready to be fitted; the bare strip is where the old cork has been cut away along with a bonded strip of copperclad which the rails were soldered to, to aid alignment over the join (a new one will be fitted prior to relaying):

 

Tracks now removed, cork and first coat of black applied (sprayed to save time):

 

As a bonus, when relaid, an eighth track will now be added to allow an extra train to be stored.

[5BarVT]

and the pivot point on the fixed part of the sector plate will be moved 2" nearer the end to compensate.

If it’s to maintain the balance about the pivot point then only a 1” move is wanted.

On the other hand I may have totally missed the real reason so should keep quiet. :-)

Paul.

[Signaller69]

If it’s to maintain the balance about the pivot point then only a 1” move is wanted.

On the other hand I may have totally missed the real reason so should keep quiet. :-)

Paul.

Hi Paul, the extension piece could be much longer without affecting the balance as the sector plate pivot is almost at the end rather than in the middle of the "fixed" (to the base framework) part, if anything the extension helps balance it more evenly so its not an issue thankfully.

[60091]

Hello Martyn

Catching up with Crinan today and more fantastic photographs.

The more I see of Crinan, the more impressive the layout becomes. Hope some day I have the opportunity to see Crinan at an exhibition.

 

Regards

Alan

Edited February 16, 2018 by 60091

[Signaller69]

Hello Martyn

Catching up with Crinan today and more fantastic photographs.

The more I see of Crinan, the more impressive the layout becomes. Hope some day I have the opportunity to see Crinan at an exhibition.

 

Regards

Alan

Hi Alan,

Thanks for your kind comments, it is much appreciated. I enjoy taking the layout to shows but don't do too many per year, which gives me time to do alterations such as those ongoing currently; Crinan has been invited to York show this Easter, Newcastle Railex in July and Wigan show in October if you are likely to be visiting any of these and I have received a few other enquiries going forward.

 

All the best,

Martyn.

[Signaller69]

Some more work done on the fiddle yard Sector Plate. The folding extension is fitted and copperclad strips glued in place either side of the join. Most of the track was removed and spaced to allow an eighth track to be installed (hence the power feeds being visible). Once happy, new/salveged track was laid over the copperclad strips and soldered onto them before using a slitting disc to cut through each rail. Isolating gaps in the copperclad to be added yet. Power is fed from a rotary switch via a jumper cable direct to the sector plate; the folding extension is electrically dead but I may add phosphor bronze contact strips across the copperclad strips yet.

 

The last photo shows the exits from the fiddle yard: the left hand track is the Distillery branch; note this cannot move right, so is only used for this purpose. The second left track is aligned with the "main line" exit, which all other tracks can align with. The 2 very right hand tracks have a fairly tight curve on the sector plate to bring them parallel with the other tracks.

 

The round head of the bolt which acts as the pivot for the sector plate can be seen in some of the photos. It is where it is in order to remove a previous sharp curve on the main line to align with the sector plate (a lesson learned with the mk.1 sector plate; the current one is mk.2!)

 

The sector plate won't win any craftsmanship awards but it works well and has so far proved immune to temperature extremes in the Club and at shows.

[The Ghost of IKB]

Hi Alan,

Thanks for your kind comments, it is much appreciated. I enjoy taking the layout to shows but don't do too many per year, which gives me time to do alterations such as those ongoing currently; Crinan has been invited to York show this Easter, Newcastle Railex in July and Wigan show in October if you are likely to be visiting any of these and I have received a few other enquiries going forward.

All the best,

Martyn.

Look forward to seeing you at york, big fan of this railway.

[Signaller69]

Look forward to seeing you at york, big fan of this railway.

Thanks, please do say hello, always nice to put a face to a name!

 

Martyn.

[60091]

Very pleased to see Crinan is coming north.. I look forward to seeing it at Newcastle Railex in July.

 

Alan

[Signaller69]

Very pleased to see Crinan is coming north.. I look forward to seeing it at Newcastle Railex in July.

 

Alan

Thanks Alan, again please say hello! Not been to that show before, looking forward to it!

 

Martyn.

[Signaller69]

In between working on the fiddle yard, the Crinan "MacBraynes" bus fleet has received a little toning down work, along with front wheels modified to a turned position to suit certain locations on the layout where this is appropriate so with them back on the layout, here are a few photos, including the obligatory cliche "bus on a bridge" shots.

Being otherwise standard commercial offerings from EFE and Corgi I accept they are probably not 100% accurate to specific MacBraynes vehicles, but the finish and the livery, which suits the era I am modelling, are far better than I could achieve with kits, even if the correct types and transfers were available.

[SHerr]

Really looking forward to seeing this at York, great atmosphere.

[Signaller69]

Really looking forward to seeing this at York, great atmosphere.

Thank you, do say hello!

[Signaller69]

"Crinan" will be Stand 19 on the ground floor at York (subject to any last minute changes the Organisers make).

 

No photos this time, but I have been busy completing the lighting facia, fitting a new rotary switch for the sector plate and tweaking a few scenic bits which required minor attention. The fuel point is having a minor reworking as the original shelter had warped badly, among with other odd jobs.

 

I have also been working on rolling stock projects and test-running stock.

 

Will hopefully get some more photos up over the next day or 2.