gormo Posted August 27, 2012 Author Share Posted August 27, 2012 G`day Folks, I seemed to have recovered from my attack of euphoria , as in the previous post above. I have put some time in on sorting out the layout plan and I am quite happy with that now. That was followed by an attack of the flu and consequently not much has been achieved this last week and a bit. I have turned my design attention, in the last couple of days, towards the bell crank. I feel it should be easier to make and I have been racking my brain to find a part that could be adapted by Joe Average and not cost the Earth. The only thing that has surfaced so far is plastic quad. A type of plastic beading ( a timber alternative ) that has quite good strength. The end profile looks like a quarter of a circle.......therefore the perfect shape, provided I can cut slices off the length at a consistent thickness. Unfortunately , this is where it becomes a little difficult for Joe. As of tonight I have achieved the consistency, but with the help of a scroll saw ( a motorised fret saw ) and an improvised jig.........Sorry Joe.!!!!.....I have made a bell crank for the test bench and it has already had a good hiding. The plastic seems to stand up to punishment. It has a memory effect, in that it returns to shape after minor distortion.......which is good.!!!...When I say minor distortion, I am referring to putting a screw through the thing and bending it out of shape...........obviously there is a point of no return.........but that seems to be well outside the normal operating limits. The thing is........a 2.4 metre length of 18mm Quad costs AU $10.80...........I am currently cutting slices at a thickness of approx. 2.5mm.........if you allow another 1mm for thickness of saw blade and wasteage and testing etc. you can come up with a pessimistic figure of 600 plus.........therefore.........AU 1.8 cents each..........pretty hard to beat. Once the saw and jig are set up, it takes very little time to knock up twenty or so of these little suckers.........so well worth the effort. Unfortunately I have left Joe behind again.........but for any of you guys out there with some equipment.........it`s a doddle. I will update with some pics tomorrow............Goodnight All..................Cheers Gormo Link to post Share on other sites More sharing options...
BRealistic Posted August 27, 2012 Share Posted August 27, 2012 We're all listening Gormo... lots of food for thought... so please carry on! By the way, was that man-flu you had... or real flu... which I'm told by those of the fairer sex is a whole lot worse!! Link to post Share on other sites More sharing options...
AndyB Posted August 27, 2012 Share Posted August 27, 2012 I have turned my design attention, in the last couple of days, towards the bell crank. Sorry, Gormo. What's a "bell crank"? You lost me already! Andy Link to post Share on other sites More sharing options...
BRealistic Posted August 27, 2012 Share Posted August 27, 2012 Andy. In case Gormo is now fast asleep, go to the very first video and the bell crank appears in the second shot, doing the job of turning the action of the rod through 90 degrees. It's the metal triangular plate with a screw fixing (to the baseboard) which acts as the fulcrum. Not much good at technical descriptions, but hope this makes sense! Link to post Share on other sites More sharing options...
AndyB Posted August 27, 2012 Share Posted August 27, 2012 Thanks, Alan. Now I've seen it I'm not embarrassed about asking! Strange name for a triangular plate! Andy Link to post Share on other sites More sharing options...
gormo Posted August 27, 2012 Author Share Posted August 27, 2012 Mornin` All, You guys have been busy while Gormo was asleep!........ Alan......it was and still is real flu.........my wife has got it too. Our 9 month old Grandson has managed to give it to the whole family whilst travelling through pretty well unaffected himself........Thank God. Thanks for explaining the bell crank.........that was a good description. Andy ......if you need more info........check out this Wikipedia link http://en.wikipedia.org/wiki/Bell_crank Must go now........many things to do..........I`ll check in later.............Cheers Gormo Link to post Share on other sites More sharing options...
BRealistic Posted August 28, 2012 Share Posted August 28, 2012 That's bad luck Gormo... never had full blown flu myself, but I know it makes you suffer. Get well soon!!!! Suppose it'll reach the UK in time for Christmas! Link to post Share on other sites More sharing options...
AndyB Posted August 28, 2012 Share Posted August 28, 2012 Thanks, Brian. Hope the flu clears up soon. Andy Link to post Share on other sites More sharing options...
gormo Posted August 28, 2012 Author Share Posted August 28, 2012 Evenin` All First of all..........thank you all for the get well wishes........we are on the mend......but it`s a slow process with this little bug.!!!!.....so we keep calm and carry on. Now .....down to business.........The first pic shows the original idea.......a Bell Crank made from 1mm Aluminium Flat Bar. The bar is 25mm wide. I determined to cut off a 25mm piece thereby creating a square. The square was then cut across the diagonal to form the shape you see here. Holes were drilled to suit. It`s not too difficult but it`s time consuming .....but it`s effective and cheap. I should point out that the holes drilled out very close to the edge are just the result of trying different configurations. They would not normally be put so close to the edge Recently I came up with trying to use the plastic quad solution........the next pic shows a short length of what it looks like pre-gormo The following shows a 2.5mm ( approx) slice taken from the end of the short length. Now overlayed on the original Aluminium version..........there`s not much difference in size and I probably prefer it to be a tad smaller. Three 3mm holes drilled to take mounting screw and CBI`s. This material is forgiving enough to allow drilling with a pin vice if you so desire. An indication of scale The next three show it mounted on the test bench. I have used a 6mm long x 3mm nylon spacer to achieve height and clearances off the baseboard. The spacers are available from electronics parts suppliers. I have also used Loctite thread locking compound to keep the little 3mm screws held fast in the CBI`s. I have not used any washers.......don`t seem to need them. The material has some nylon properties however it is definitely not Nylon. I thought a video showing my method of cutting may be of some value, so that is entered below I think the important thing that the video shows, is the fact that you can give these little devils quite an unreasonable hiding, and amazingly they survive in good condition. I will over supply myself with spares to avoid setting up the saw every now and then. I think the crank will give a good length of working life.............Time will tell..............................Cheers Gormo Link to post Share on other sites More sharing options...
gormo Posted September 1, 2012 Author Share Posted September 1, 2012 G`day Folks Another update from the test bench. All was going well until I realised there was some unwanted movement in the bellcrank. The area where the main pivot screw goes through was starting to get a bit sloppy........it`s nothing drastic.......but something to take into account before we get too committed on specifications. The thing to bear in mind also is that this little sucker has had a hard life already..........but I like to build `em to last..........so back to the drawing board. The solution seems to be at this stage........and I may be proven wrong........to just make the crank thicker. That`s what I`ve done today...........I`ve nudged it out to about 3.5mm........big deal you say.........well percentage wise it`s quite a lot.........so we`ll see how it goes. The testing I`ve done so far shows that it is far superior to the thin version.......fingers crossed because I like this method and I hope it works out this time. There are some pics below showing the new crank. One thing I have done as well is replaced the nylon spacer with a nyloc nut. I want the CBI`s to just clear the baseboard surface so that they line up better with the wire in cable. In addition a video........you will notice in the second half of the video that it shows the thin bellcrank working and the movement or play mentioned above is just noticeable. As stated above.....it`s no big deal.........but I am a perfectionist as you may have already guessed........so I would rather persevere and try and improve it. http://www.youtube.com/watch?v=SffEIPy82SE There you go folks..........I`ll keep you posted as things develop......Cheers Gormo Link to post Share on other sites More sharing options...
milkman matt Posted September 1, 2012 Share Posted September 1, 2012 Just found this topic (and read all 8 pages) and found it most interesting. If I might venture a suggestion. For spacers on the bell cranks, could you use the top part of the choc block that houses the screw? Link to post Share on other sites More sharing options...
AndyB Posted September 1, 2012 Share Posted September 1, 2012 Just a thought, Brian, but would it be possible to ditch the choc-block connectors and simply bend the moving rod through 90degrees at the tip and poke it through the hole in the bell crank? Whilst I was typing this Milkman Matt pitched in with an interesting idea, too.... Andy Link to post Share on other sites More sharing options...
milkman matt Posted September 1, 2012 Share Posted September 1, 2012 I see what your getting at Andy but, what if you wanted to make adjustments? Link to post Share on other sites More sharing options...
gormo Posted September 1, 2012 Author Share Posted September 1, 2012 Just a thought, Brian, but would it be possible to ditch the choc-block connectors and simply bend the moving rod through 90degrees at the tip and poke it through the hole in the bell crank? Whilst I was typing this Milkman Matt pitched in with an interesting idea, too.... Andy Hi Andy Yes that idea will work and has worked...........that`s the configuration I had when I first started playing around with this idea. The CBI`s make it a lot easier to set up and adjust..........so I will stay with them I think. Cheers Brian Link to post Share on other sites More sharing options...
gormo Posted September 1, 2012 Author Share Posted September 1, 2012 Just found this topic (and read all 8 pages) and found it most interesting. If I might venture a suggestion. For spacers on the bell cranks, could you use the top part of the choc block that houses the screw? Hi Matt I never thought of that???????........I`m going out to the shed now to measure one of those things........it might just work..........thanks for the input............Cheers Gormo Link to post Share on other sites More sharing options...
milkman matt Posted September 1, 2012 Share Posted September 1, 2012 While you're out there....See if you can mount a bell crank on on an angle bracket so that it is at 90 degrees to the board and therefore suitable for signal operation? Link to post Share on other sites More sharing options...
gormo Posted September 3, 2012 Author Share Posted September 3, 2012 G`day Folks, Bad news I`m afraid !!!!.............the plastic quad bellcrank has failed a strength test on three occassions now. When I use the lever and apply a significant pulling force on the system........(.imagine trying to stretch the cables as opposed to pushing the cables).........the bellcrank has failed at the CBI connection point. I have tried moving the holes further away from the edges but to no avail. So there you go........three strikes and you`re out in my book. Back to metal and the drawing board.............Cheers Gormo Link to post Share on other sites More sharing options...
BRealistic Posted September 3, 2012 Share Posted September 3, 2012 ... or maybe the easiest option... 'the snake'!!?? Link to post Share on other sites More sharing options...
AndyB Posted September 3, 2012 Share Posted September 3, 2012 Could you try using a bit of MDF or similar? Might be more resilient than plastic? Andy Link to post Share on other sites More sharing options...
gormo Posted September 3, 2012 Author Share Posted September 3, 2012 G`day Again, Well you guys will think I might be losing the plot, because I`ve realised the problem with the plastic and I think I`ve cured it. ..............The problem is Gormo..............The amount of pressure being applied by me was in a nutshell " excessive ".......it was also amplified by the lever. Regardless of material used.........with that sort of testing .....something would give way. So I walked away from it.........had a think about it.........loosened off the pivoting screws and generally freed up the system .......and guess what..........it works fine with normal use. Sorry to all for the stupid post..............I`m building scale models .........not the real thing...............so the tolerances should be scaled down as well. The result is perfectly acceptable and will withstand sustained normal use for thousands of movements. I`m just going outside to smack myself in the mouth and see if that brings me back to reality. Goodnight all...................Gormo Link to post Share on other sites More sharing options...
gormo Posted September 5, 2012 Author Share Posted September 5, 2012 Aaaahh!!!!!!................that feels better. Well folks........everything is OK.........the bellcranks are performing well under normal conditions and I really can`t expect any more than that. I have started a trial with some rod, instead of cable, working the the linkages.......it`s very good...........quite a positive and smooth action. As guides for the rod I am using some small cable clips spaced at about 100mm. I think the rod is superior to cable over a short distance (maybe 600mm or 2 feet ) but time and testing will tell. Pics and more to follow.....................Cheers Gormo Link to post Share on other sites More sharing options...
gormo Posted September 5, 2012 Author Share Posted September 5, 2012 G`day Folks, A couple of pics as promised...........The first pic showing rods connected. The cable clips act as guides but their role is not critical to the operation The second shows bellcrank and rods Finally another video showing the rods and cranks in operation All for now......................Cheers Gormo Link to post Share on other sites More sharing options...
AndyB Posted September 5, 2012 Share Posted September 5, 2012 Nice one, Gormo. I particularly like the way you get the crank to move in time with the music. Andy Link to post Share on other sites More sharing options...
gormo Posted September 7, 2012 Author Share Posted September 7, 2012 Thanks Andy The crank is easy compared to the music timing...............only joking!!!.........if the music fits......it`s a happy accident Cheers Gormo Link to post Share on other sites More sharing options...
Castle Posted September 7, 2012 Share Posted September 7, 2012 Hi All, I am off work ill today so this thread has proved a very welcome read. Very interesting and I have a real interest in doing a mechanical point control system when (if!) I ever get round to building the layout in my head! I think it adds something to a steam era layout as it is how it was done on the real thing. The steam era infrastructure was heavily labour intensive and required a lot of human effort and interaction to make it all work and this is a great miniature version of it! It is also one of the reason I like scale couplings (other than aesthetics) and I am willing to accept the obvious limitations and inconveniences. Just a thought on the bell cranks - the wear may be due to the plastic bring worn away on the threads of the screws. Had you thought of either bushing the plastic with a metal tube or using screws / bolts with plain sections on them to eliminate this? I hope this helps! All the best, Castle Link to post Share on other sites More sharing options...
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