My 7mm dabblings
- Thread starter mickoo
- Start date
mickoo
Western Thunderer
Afrad not LOL, but I did have a thought on the plane over to resize for 1:32, it'd need a shuffle around to keep within PPD material sizes, and some parts that interlock would need their dimensions altered to suit the new size and material thickness, but perfectly possible.
Dog Star
Western Thunderer
I seem to recall that you have said you were receiving encouragement for a garden railway... what scale / gauge is Mrs. Dikitriki expecting?Good man.
1/32 Resin body next please
If a scale greater than 7mm:1... you shall need to be sure that Gromit and the Penguin are not an underlying feature of that encouragement.
regards, Graham
richard carr
Western Thunderer
Mick
It all looks wonderful, very impressed. I think PPD do a very good job.
The only difficult thing is just how easy it is to make a mistake when doing the etches.
I look forward to seeing more
Richard
It all looks wonderful, very impressed. I think PPD do a very good job.
The only difficult thing is just how easy it is to make a mistake when doing the etches.
I look forward to seeing more
Richard
mickoo
Western Thunderer
Richard, only made one mistake so far, which I'm pleased about, not the mistake....but that it's only one. There are a couple of things I'd change on hind sight, mostly to do with material choice and thickness and ease of forming some parts, but other than having two left hand frame stiffeners it's all perfectly useable.
mickoo
Western Thunderer
Just a small update, hard to stay focused on the previous etch work with a head full of GE sounds and images LOL
Just added the other two pipes, still need the larger one on the left side and a couple of clips/brackets to hold them in place,added the splashers as well, bit of a faff as the face is a separate part and could really be a fold up of the frame top flange, but getting them centred could be difficult due to the sweeps up and down that part makes, it'll need some careful measuring and some even more careful bending to make sure the splasher is centred over the wheel.
I reworked some of the etch whilst away, improvements rather than errors, could do a few more and then it'd be time to draw closure on it, you could probably continue tweaking for several versions yet but I don't want to keep running up phototool costs for minor tweaks that could easily be overcome with a little effort in construction.
Need to think about an inner chassis at some point and affixing it to the existing structure and probably incorporating it into one etch rather than two.
As an etching exercise it has certainly served me very well.
Just added the other two pipes, still need the larger one on the left side and a couple of clips/brackets to hold them in place,added the splashers as well, bit of a faff as the face is a separate part and could really be a fold up of the frame top flange, but getting them centred could be difficult due to the sweeps up and down that part makes, it'll need some careful measuring and some even more careful bending to make sure the splasher is centred over the wheel.
I reworked some of the etch whilst away, improvements rather than errors, could do a few more and then it'd be time to draw closure on it, you could probably continue tweaking for several versions yet but I don't want to keep running up phototool costs for minor tweaks that could easily be overcome with a little effort in construction.
Need to think about an inner chassis at some point and affixing it to the existing structure and probably incorporating it into one etch rather than two.
As an etching exercise it has certainly served me very well.
mickoo
Western Thunderer
Well, finally found a little time between researching GE AC4400CWs and the ilk to have a look at the 08 door stampings.
Overall the etches are nice and the half etch fits the thinner stampings for the hinges and catches areas and these mostly line up with the kit give or take a few 0.01mm here and there.
However, I am at home to Capt' cock up and his merry band of men big time, all the etches are the correct height for their respective doors, every single one is too narrow by 1-1.5mm, now how the hell that happened I have no idea as they were all measured with a digital vernier and all other measurements are correct.
So it's the bin for the lot and a whole new photo tool and artwork and associated cost therein, which then brings tot fore of perhaps doing it the way David suggested and making a whole new door with the stampings already etched on, all be it only one depth unlike the dual depth currently and prototypically, it'd also mean unsoldering the doors on the current kit to use them.
I think some more UP and BNSF research is the order for the rest of the evening...before I throw something very expensive at something very hard! LOL Or start editing some of my 800+ CSX loco detail images from Florida.
Overall the etches are nice and the half etch fits the thinner stampings for the hinges and catches areas and these mostly line up with the kit give or take a few 0.01mm here and there.
However, I am at home to Capt' cock up and his merry band of men big time, all the etches are the correct height for their respective doors, every single one is too narrow by 1-1.5mm, now how the hell that happened I have no idea as they were all measured with a digital vernier and all other measurements are correct.
So it's the bin for the lot and a whole new photo tool and artwork and associated cost therein, which then brings tot fore of perhaps doing it the way David suggested and making a whole new door with the stampings already etched on, all be it only one depth unlike the dual depth currently and prototypically, it'd also mean unsoldering the doors on the current kit to use them.
I think some more UP and BNSF research is the order for the rest of the evening...before I throw something very expensive at something very hard! LOL Or start editing some of my 800+ CSX loco detail images from Florida.
mickoo
Western Thunderer
Ok, just a small update, got my wheels back from Colin all S7'd and the axles from JP so time to get on with the chassis, so puzzle number one was which axle to drive and finally decided on the middle one, simply because I've no confidence that I can get the split knuckle rods to drive effectively through the split and all work nicely, which effectively makes my 0-6-0 an 0-4-(0-0)-4-0, therefore no compound errors in my sloppy rods or horn guides to contemplate.
The early choice of driven axle was good as the next stage of getting said wheels onto said axles means that once on, there not coming off! I understand the taper should be tight, but I had to hammer the axles home with some force to get them all the way on, turns out the 10thou taken off the back face may well have had a small contributing factor in reducing the effective taper size on the wheel? None the less five were driven home and are effectively sealed for life, a puller might get them off but it'd have to tuck right into the boss as if not it'll surely break the plastic spokes.
For the last, as it's going to be on and off a bit, I decided to sacrifice some tightness and just ran a file over the axle taper, instead of the 1mm gap at hand tightness (last 1mm driven home under force), I've about 0.25 and even hand pushed home there's still about a 0.05-0.1mm gap for the last big push, said modified taper is clearly marked LOL.
So onward, gearboxes, just as a trial I ran with the Roxey 13:1 coupled to a Mashima 1833 that came in one of my recent kit purchases, whilst it ran there were a miriade of issues, it's almost impossible to fold up square
, I have another to try later, but it ran and said vehicle moved across said work bench, even though driven by one centre axle in a satisfying manner. Second issue was side float on the gear wheel, depending on direction of travel, said gear wheel like to impart a side force and move the axle correspondingly, not a problem if theres room for the motor gearbox combo to follow, in my case the hole for motor gearbox combo doesn't, thus on impacting the side of the chassis then imparts a twist and lifts the axle correspondingly....not impressed.
So with all those issues I decide to junk the Roxey gearbox and recover ball bearings for use in the new super dooper S Dale gearbox, first off it folds up perfectly, I decided to construct it in idiot style, no cleaning, no scoring, no care, just fold up, open bearing holes for ball races, insert shaft and motor and run, worked perfect right out off the bat, very impressive.
Having confirmed it was a million times better than the previous experience I went back and soldered up and fettled clean, again side play is an issue so some washers in there are a must.....or a new idea I have, getting exact spaced washers to fit in there might be a problem, so I have come up with a simpler (I think) solution which requires rubber tubing cut to length, this will ensure the gear wheel stays exactly centred on the worm and will push against the inner race of the ball bearings so should be a perfect fit as rubber tube is easier to cut to size and if overly long by a few thou can and will be compressed to take up the slack (photos later on this evening once in practice).
One thing I did find was that Stephs is a much shorter box than Roxey and the Roxey worm is too long as it has a grub screw retainer, so part of the front of the gear box was removed to accomodate the worm, which still didn't work as the end of the worm near the grub screw does not clear the teeth on the gear, I have a solution for that (the correct way would have been to get the correct gears from Steph! but I was in full bodging mode yesterday LOL) and will trim off the grub screw end of the worm and affix worm accordingly. I only mention that as someone will look at forecoming photos and wonder what an earth I have done LOL.
The next problem is of course the ratio, it's stupid high for an 08, even at 4v it whizzes along the desk at a silly high speed, so whilst this gear box will not remain it is proving several issues before the main one goes in and allowing experiance to be gained before the 'right' one is installed.
Which begs the question, which gearbox do I ultimately use, of course the ABC two stage would be perfect, but at a cost and do you really need that quality, most will answer yes, but honestly, do you? Are there alternatives, I'm looking at the Roxey two stage 40:1 and working on the premis that my previous bad experience is down to my ineptitude. What I'd like to do is perhaps work up an etch for a slow speed gear box and try as I might I cannot find the same worms that ABC seem to use, they look to be more pitched than those readily available, I'm using a twin start worm but ABC seem to use a four or even five start worm, which is clearly how they get them so free running and allow the loco to run on.
I've also seen many fine models move at crawling speed, quite critical for the 08 to be fair, they can't all be using ABCs can they? So there must be other alternatives around, all of which falls into what Steve O is looking into and from previous discussions here and elsewhere.
For the record, current tests were done under DC, a 40yr old H&M truth be told LOL, so I accept DCC might give a mildly better slow speed control
The early choice of driven axle was good as the next stage of getting said wheels onto said axles means that once on, there not coming off! I understand the taper should be tight, but I had to hammer the axles home with some force to get them all the way on, turns out the 10thou taken off the back face may well have had a small contributing factor in reducing the effective taper size on the wheel? None the less five were driven home and are effectively sealed for life, a puller might get them off but it'd have to tuck right into the boss as if not it'll surely break the plastic spokes.
For the last, as it's going to be on and off a bit, I decided to sacrifice some tightness and just ran a file over the axle taper, instead of the 1mm gap at hand tightness (last 1mm driven home under force), I've about 0.25 and even hand pushed home there's still about a 0.05-0.1mm gap for the last big push, said modified taper is clearly marked LOL.
So onward, gearboxes, just as a trial I ran with the Roxey 13:1 coupled to a Mashima 1833 that came in one of my recent kit purchases, whilst it ran there were a miriade of issues, it's almost impossible to fold up square
, I have another to try later, but it ran and said vehicle moved across said work bench, even though driven by one centre axle in a satisfying manner. Second issue was side float on the gear wheel, depending on direction of travel, said gear wheel like to impart a side force and move the axle correspondingly, not a problem if theres room for the motor gearbox combo to follow, in my case the hole for motor gearbox combo doesn't, thus on impacting the side of the chassis then imparts a twist and lifts the axle correspondingly....not impressed.So with all those issues I decide to junk the Roxey gearbox and recover ball bearings for use in the new super dooper S Dale gearbox, first off it folds up perfectly, I decided to construct it in idiot style, no cleaning, no scoring, no care, just fold up, open bearing holes for ball races, insert shaft and motor and run, worked perfect right out off the bat, very impressive.
Having confirmed it was a million times better than the previous experience I went back and soldered up and fettled clean, again side play is an issue so some washers in there are a must.....or a new idea I have, getting exact spaced washers to fit in there might be a problem, so I have come up with a simpler (I think) solution which requires rubber tubing cut to length, this will ensure the gear wheel stays exactly centred on the worm and will push against the inner race of the ball bearings so should be a perfect fit as rubber tube is easier to cut to size and if overly long by a few thou can and will be compressed to take up the slack (photos later on this evening once in practice).
One thing I did find was that Stephs is a much shorter box than Roxey and the Roxey worm is too long as it has a grub screw retainer, so part of the front of the gear box was removed to accomodate the worm, which still didn't work as the end of the worm near the grub screw does not clear the teeth on the gear, I have a solution for that (the correct way would have been to get the correct gears from Steph! but I was in full bodging mode yesterday LOL) and will trim off the grub screw end of the worm and affix worm accordingly. I only mention that as someone will look at forecoming photos and wonder what an earth I have done LOL.
The next problem is of course the ratio, it's stupid high for an 08, even at 4v it whizzes along the desk at a silly high speed, so whilst this gear box will not remain it is proving several issues before the main one goes in and allowing experiance to be gained before the 'right' one is installed.
Which begs the question, which gearbox do I ultimately use, of course the ABC two stage would be perfect, but at a cost and do you really need that quality, most will answer yes, but honestly, do you? Are there alternatives, I'm looking at the Roxey two stage 40:1 and working on the premis that my previous bad experience is down to my ineptitude. What I'd like to do is perhaps work up an etch for a slow speed gear box and try as I might I cannot find the same worms that ABC seem to use, they look to be more pitched than those readily available, I'm using a twin start worm but ABC seem to use a four or even five start worm, which is clearly how they get them so free running and allow the loco to run on.
I've also seen many fine models move at crawling speed, quite critical for the 08 to be fair, they can't all be using ABCs can they? So there must be other alternatives around, all of which falls into what Steve O is looking into and from previous discussions here and elsewhere.
For the record, current tests were done under DC, a 40yr old H&M truth be told LOL, so I accept DCC might give a mildly better slow speed control
Steph Dale
Western Thunderer
Mick,
Yeah, the 13:1 with a Mashima is going to be way too fast, remember it's designed for wheels under 3'9" in diameter; even then that gives a scale 60-70mph. I suggest that something around 40:1 would be a better choice. If you're not in a rush you may decide to watch this space.
In terms of running in an 08, I suspect a lot of people are using the recommended Portescap motor unit.
Steph
Yeah, the 13:1 with a Mashima is going to be way too fast, remember it's designed for wheels under 3'9" in diameter; even then that gives a scale 60-70mph. I suggest that something around 40:1 would be a better choice. If you're not in a rush you may decide to watch this space.
In terms of running in an 08, I suspect a lot of people are using the recommended Portescap motor unit.
Steph
mickoo
Western Thunderer
93rpm at the axle for a 15mph CL08, or 124rpm for the 20mph variants
If our motor is running at 9000rpm then thats 72:1 for the higher speed?
One thing that always puzzles me is that all gearbox specs are for motors running at max speed, why! Has no one ever heard of speed control, I mean, my car can do 140mph but amazingly by adjusting the pressure under my right foot it can go as slow as 70mph or even....get this 30mph! You'd think modellers would apply the same logic to their hands and apply less power to their model locos to achieve the required speed.
Yes, it does mean the loco will never overspeed and yes the higher the ratio will give smoother control but I suspect marginal between 72:1 and 40:1, but when running at near top speed that little ole motor is going to scream its heart out, get awfully hot in the process and probably do itself a mischief LOL. High speed motors also ramp up the noise level and brass models acoustically amplify that as well as any vibration you may have which will also be amplified.
Maybe I got it all wrong, but instead of 72:1 ratio I'd drop for say 40:1 so the motor isn't running as fast or hot, and then limit the top speed either manually with my finger. Or I'm sure the curve can be manipulated in a DCC CV to prevent it going over what is effectively half speed for the gear ratio. Like I say, maybe I got it all wrong LOL.
The other option I suppose is to go for a motor whos top speed is say 17,000rpm and couple it to a 72:1 gearbox, thus at prescribed speed it'd only be running at half RPM and still give a good slow speed ratio.
Comments not aimed at you or anyone personally, just happened to be the opportune moment to air my views on something that's been puzzling me for a while.
I've a couple of Buhlers here from a DJH motorising kit, anyone have any data on these motors, there's no spec on the casing other than Buhler, they are enormous and wont fit in the 08 unless I angle the drive line, currently prefering a vertical set up to leave space for speaker and acoustic chamber.
mickoo
Western Thunderer
Steph, not sure what the 'recommended' 08 package is, Portescap motor unit means nothing to me, will look that one up later LOL. The comment was aimed more openly than just the 08 to include anything with wheels that sort of size and speed, aka Jintys and other steam / diesel locos etc. What motor gearbox combos are others using, feedback etc.
I'm not in too much of a rush, the 13:1 is good enough to test movement, appeases my child itch to 'make it move' and is the opportuity to learn something new and experiment, and, I 'am' watching that space! The tendency for the gear wheel to traverse left or right under load depending on direction was a new one on me, thus throwing the gear centres off and thus reducing the efficiency. I suspect a little lateral play is acceptable, but 5mm is not a little in these cases
.I'm also keen to find that primary worm drive ABC uses, the pitch is very course and I reckon the ration is very low, almost 3:1 or even 5:1, no good as a final drive but good for primary if multi geared to get the required speed. The low ratio and thus low dia axle gear makes it very suitable for diesel motor applications, your reduction ratio being done elsewhere, I'm thinking drive shaft technology here along the lines of your remote units, if your going for drive shaft technology then it'd make sense to keep the remote (or traction gearbox) as small as possible and use a larger reduction gearbox buried inside somewhere. I'm thinking locos with wheels as small as 750mm here but nominally 900mm, luckily they are driven by shafts 1:1 so no issue hiding it
but even for DE power it's something I keep kicking around.
S
SteveO
Guest
I took my little Sentinel to the club last week, which uses a Roxey 40:1 gearbox with Mashima 1833. It was amazingly fast! Slow speed control (admittedly over our new and in-progress layout track) was quite difficult to maintain without using the switches on our ancient H&M to drop voltage or amps or whatever they control. I reckoned on a 60:1 ratio would be much better suited to provide a better controlled smooth take off without the need to move the control knob with micrometer-calibrated fingers!
richard carr
Western Thunderer
Mick
A Portescap is a motor motor gearbox in the &mm version they come in in either 23:1 ratios or 31:1 ratios (or very close to those). They have been around a long time and at one point were probably the only 7mm motor gearbox that was easily available, today though I believe they are out of production and no longer available new. They are still very popular and fetch good prices on Ebay often in excess of £100. They are an excellent motor gear box combination with a powerful 1/2 watt coreless motor, I have several of them in various steam locos, however they are useless in mainline diesels the gear ratio is far too high. The 31:1 ratio is probably fine for 08 and was I imagine that this is what the kit was designed around.
Today there are numerous other options out there for my diesels I generally prefer the offerings from ABC.
Richard
A Portescap is a motor motor gearbox in the &mm version they come in in either 23:1 ratios or 31:1 ratios (or very close to those). They have been around a long time and at one point were probably the only 7mm motor gearbox that was easily available, today though I believe they are out of production and no longer available new. They are still very popular and fetch good prices on Ebay often in excess of £100. They are an excellent motor gear box combination with a powerful 1/2 watt coreless motor, I have several of them in various steam locos, however they are useless in mainline diesels the gear ratio is far too high. The 31:1 ratio is probably fine for 08 and was I imagine that this is what the kit was designed around.
Today there are numerous other options out there for my diesels I generally prefer the offerings from ABC.
Richard
mickoo
Western Thunderer
Richard,
Being new to the sport so to speak would explain why I have little knowledge of things past, and hence a tendency to often re-invent the wheel LOL, thanks for the info, much appreciated.
ABC are certainly king of the hill and command a price accordingly, however technologically they are not a lot removed from any other multi stage gearbox, it's the choice of gears and machine work that make the difference, the key being that 1st stage low ratio worm gear which removes a lot of the noise associated with worm gears and allows the gear train to drive back through the motor.
Kindest
ZiderHead
Western Thunderer
You will want to double-check this as its been a long time since I was taught this stuff but IIRC DC motors all have the same kind of power/rpm/efficiency curves so the same basic rules apply to all of them. The specs always show the no-load rpm for their rated voltage, and sometimes the rated.
Max torque is at 0rpm, max power is at 50% no-load rpm, max efficiency varies, but somewhere 80-90% no-load rpm. This may be given as the rated rpm and is the highest you can run it under load, to be on the safe side I was told to use 75% of the no-load rpm if you dont know the rated.
A quick google shows the 1833 at 12V is no-load at ~9,400rpm and rated at ~8,500, so 8,500 is the absolute max speed it should run at under load. 8,500/135 = 63:1 for 15mph, or 8,500/180= 47:1 for 20mph. That should crawl along pretty nicely
Jon
* edited for bad maths
Dikitriki
Flying Squad
Hi Mick
I would argue that the ex Ron Chaplin gearboxes now sold by MSC are better, for the simple reason that the gearbox frame is machined from solid rather than fabricated (same sort of gear train etc). I would also argue that very few of the ABC gearboxes are square.
It doesn't stop me using them, as they still seem to run very smoothly and are DCC friendly.
I use Portescap (RG7) motors in some shunting locos, and the controllability is superb. They whine at higher speeds, and I would not put them in MT locos or diesels.
Regards
Richard
mickoo
Western Thunderer
That's odd as the Sentinel has tiny little wheels so I'd guess 40:1 should be ok?
Sounds also like you were running DC and not DCC?, I think (guessing here) you can adjust the speed curve in DCC so that 100% input only gives 50% output I.E digitally cap the top speed, if that is so then you can adjust the whole speed curve to make the first 50% of the controller control the first 20% of the speed and the other 80% in the last 50% of the controller, where such close speed control is not generally required.
We do the same at work with the crane joystick, the first 50% controls the lower 10% of the speed range where you need fine control for landing boxes on trailers 120 feet below you, the rest of the 50 controls the other 90% of the speed range, well it doesn't actually, it controls the next 40% up to half speed, what we call base speed. the last and highest speeds 50%+ are controlled by the load dependent system which measures the load and field weakens accordingly.
So with an empty crane the driver controls the lower 50% and the LD controls the top end and gives a total of 100% speed, with 40t on the driver controls the lower 50% and the LD calculates the load and applies no field weakening and thus the crane runs at 50% with the joystick hard over at 100%. Takes a while to get your head around but does allow for very fine control and safe heavy load high speed operation /end] OT speed controllers LOL