Any Question Answered

[John Brenchley]

14 hours ago, Chris Higgs said:

 

Read this thread. 

Photos of a DC1 wagon with a DCIII-like conversion to cross-cornered. Looks like you can build this hybrid from the etch.

 

Chris

 

 

 

I too have built these two wagon kits and some notes of which diagram I thought they represented and which style of braking I used can be found on this blog post.  I agree, DC1 converted to cross cornered operation is indeed possible.

 

 

Best wishes

 

John

[justin1985]

20 hours ago, Nigelcliffe said:

Clearly building a chassis is possible.   Essentially need to adapt/copy commercial designs, gear all the wheels together, bring it up to a worm drive, and have a drive shaft with a universal joint out to a motor.   Hardest bit, in my view, is pivoting the bogie on the chassis.   One method was written up in the old "split frame chassis book" which I edited something over 20 years ago. 

 

 

I've been chatting with @Lacathedrale and giving this a bit more thought. I was reminded of @Izzy 's post about his Cl.15 diesel built using Bachmann USA spare part bogies:

 

 

This made me think - it seems like there are basically two commercial design approaches in N scale diesels:

 

• Worm mounted on a rigid longitudinal shaft. Bogie retained by clips, but the gear that meshes with the worm seems to effectively act as the main pivot itself - doesn't it? This seems to be how Izzy's Bachmann Fairbanks-Morse bogie works. Presumably this means the mesh between the worm and its gear is VERY loose? It also seems like the gear that meshes with the worm is always straight, rather than helical cut? I imagine this means that the cut of the worm itself is different from the ones we tend to use in 2mm? Is there a proper terminology for all this?
   
• Worm mounted as part of the bogie assembly and driven by a universal joint. This seems much more familiar to a normal 2mmFS chassis design (basically the same as a tender steam loco) , and I'm sure I've seen this approach in plenty of Farish chassis. As Nigel says, providing a satisfactory bogie pivot on a scratch build is a bit of a challenge. 

Basically I'm wondering whether there is the possibility of a 3D-printed pivot/clip/bogie frame type assembly to help reduce the dependence on RTR donors for this kind of project. Perhaps replicating the design of Izzy's Bachmann USA example, if suitable gears/worms are available? (I wonder whether hobby robotics might be a source of suitable gears etc?)

 

 

Justin

[Chris Higgs]

54 minutes ago, justin1985 said:

 

I've been chatting with @Lacathedrale and giving this a bit more thought. I was reminded of @Izzy 's post about his Cl.15 diesel built using Bachmann USA spare part bogies:

 

 

This made me think - it seems like there are basically two commercial design approaches in N scale diesels:

 

• Worm mounted on a rigid longitudinal shaft. Bogie retained by clips, but the gear that meshes with the worm seems to effectively act as the main pivot itself - doesn't it? This seems to be how Izzy's Bachmann Fairbanks-Morse bogie works. Presumably this means the mesh between the worm and its gear is VERY loose? It also seems like the gear that meshes with the worm is always straight, rather than helical cut? I imagine this means that the cut of the worm itself is different from the ones we tend to use in 2mm? Is there a proper terminology for all this?
   
• Worm mounted as part of the bogie assembly and driven by a universal joint. This seems much more familiar to a normal 2mmFS chassis design (basically the same as a tender steam loco) , and I'm sure I've seen this approach in plenty of Farish chassis. As Nigel says, providing a satisfactory bogie pivot on a scratch build is a bit of a challenge. 

Basically I'm wondering whether there is the possibility of a 3D-printed pivot/clip/bogie frame type assembly to help reduce the dependence on RTR donors for this kind of project. Perhaps replicating the design of Izzy's Bachmann USA example, if suitable gears/worms are available? (I wonder whether hobby robotics might be a source of suitable gears etc?)

 

 

Justin

 

 

Well, obviously in the first design type the worm itself cannot be the pivot. It is located at the pivot point, but the pivoting is typically provided by a circular hole in the chassis into which the bogie clips.  Farish, Dapol etc are all like this. - even when a universal joint is also used (for example the Dapol 121 /122 DMUs) The worm is indeed much coarser than 2mm Association ones and the wormwheel quite thin to allow the pivoting. Works very effectively of course, but does not provide a massive gear reduction.

 

The universal joint approach is seen very often in 4mm Bachmann locos (amongst many others) and is quite fiddly to assemble. The pivot Bachmann use is a screw mount located above the pivot point and is not very durable under reassembly.

 

Both designs use a lot of gears in the train and plastic is much quieter and cheaper than the brass ones we tend to use in 2mm steam locos. Likely you would end up paying as much for the gears as you would cannibalising  RTR models. Any design using gear types from elsewhere would probably become obsolete pretty quickly.

 

Chris

Edited June 5, 2020 by Chris Higgs

[justin1985]

24 minutes ago, Chris Higgs said:

Well, obviously in the first design type the worm itself cannot be the pivot. It is located at the pivot point, but the pivoting is typically provided by a circular hole in the chassis into which the bogie clips.  Farish, Dapol etc are all like this. - even when a universal joint is also used (for example the Dapol 121 /122 DMUs) The worm is indeed much coarser than 2mm Association ones and the wormwheel quite thin to allow the pivoting. Works very effectively of course, but does not provide a massive gear reduction.

 

The universal joint approach is seen very often in 4mm Bachmann locos (amongst many others) and is quite fiddly to assemble. The pivot Bachmann use is a screw mount located above the pivot point and is not very durable under reassembly.

 

Both designs use a lot of gears in the train and plastic is much quieter and cheaper than the brass ones we tend to use in 2mm steam locos. Likely you would end up paying as much for the gears as you would cannibalising  RTR models. Any design using gear types from elsewhere would probably become obsolete pretty quickly.

 

Chris

 

I'll never deny my ignorance in mechanical matters! 

 

Where is the weight carried from chassis to bogie in the first design? Is it through the whole rectangular surface of the top of the bogie, if its not through the worm/gear interface? I've never fiddled with a commercial chassis with this question in mind, but I seem to recall the bogies seeming to have quite a lot of free movement in all directions about the interface with the worm? The clips in the circular hole clearly don't carry any of the weight, they just guide the movement. 

 

I was half wondering about using spare gears sold for Farish, which seem pretty standard and not too hard to get hold of - its the worm/worm gear that seems a puzzle to source.

 

Justin

 

[-missy-]

Hi Justin.

 

The way I dealt with what I needed was to use an original farish chassis (which had the correct wheelbase) then reverse engineer the bogies to suit what I needed. The middle bit of the bogie has been designed to match the original farish design and on the test print it clipped into the farish bit no problems. The design used the same single gear which engages with the farish worm. I have also maintained the same MOD 0.3 gears throughout the assembly.

 

Julia.

[Izzy]

As you might imagine wanting power units for several EMU’s & DMU’s I have looked at this problem quite a bit. The design of the bogies that I used in the CL15 is the same basic design that is also now standard in most N gauge locos. Graham Farish used it way back in their early designs but Bachmann changed many to the other design of a whole pivoting bogie with drives using uj’s when they first moved production to China, following the pattern used for USA models. That all these are now being produced with the CL15 type shows which is seen as easier/cheaper/better. 
 

The problem with the pivoting drive shaft type is having enough room to allow bogie rotation and that the primary pivot location for the drive must be at the bogie pivot position. This requires length which many models such as the CL15 don’t have. The pivot around the worm type overcome this need since the drive shafts are straight and can indeed be fixed. In fact the Farish DMU/EMU power plants - and the CL25/25 - have one worm on directly on the motor shaft ( the units of course only drive one bogie). 
 

You are correct the gear design is adjusted to allow the straight cut worm wheel teeth to rotate in the worm. It is a case of making the wormwheel as reasonably thin as possible rather than over cutting the tooth profiles. 

The drawback with these plug-in bogies is that unless they are tightly toleranced then they tend to move back and forward in the frames as the direction is changed. That is why most Farish ones are tight in the frames and often difficult to pull out. The Dapol 153/156 are well known for being loose and often just dropping out......

 

You will see on my Priory Road thread I have currently bodged up a bogie with a small coreless motor hung on it for my current 2-car 309 build. Doing this has overcome the bogie shift issue and trying to produce a plug-in type. The gear ratio is just 15-1, which is all most Farish diesels/DMU/EMU’s use and which seems to be quite adequate. Trying to arrange a higher gear reduction might be difficult. I was just lucky with the final design of the CL15 that I could add a further reduction stage via the belt drive. With DCC it’s no real problem when combined with such as Zimo/CT decoders. But it was fine with DC. I do believe this low gear ratio is why motors in models have flywheels. To give the motors a load to damp them down at low revs as much as possible. 
 

If you can get them I am of the opinion that the Farish DMU/EMU power plants are the best to use. Yes, they seem expensive for just a single 4-wheel drive when removed from a doner unit but can easily be fitted with fitted with drop-in wheels of the right size (6mm) or even fitted with 7mm ones Many EMU’s had up to 42” wheels. Only newer types have smaller. They are also compact leaving room for an interior in most cases. The design is also good with weight distribution, being concentrated over the drive wheels. The clips do carry/transfer the weight. The gears can’t/shouldn’t. They would not be able to turn easily, and would soon wear out. And the poor old motor wouldn’t be able to cope either. 
 

No easy, simple, cheap answers really, l’ve tried to find them......!

 

cheers,

 

Izzy

 

[nick_bastable]

The Farish units work for me and Im a arch bodger,  although I was lucky and in funds at the the time so grabbed 3 sets of the twin motor version when Hattons had them on clearance, all of which are destined for future projects.  There is also the original Fraish motor bogie although they are noisy and hopeless.    The Tomytec HM-01  shows potential however like most models is batched produced and hard to find at a sensible price at the moment from memory they where about £25 when first released 

 

Nick B

[D869]

A interesting topic. The question of custom diesel and electric loco/MU chassis is one that I have pondered on several occasions. Usually for things where an RTR chassis with the right dimensions is not available.

 

I completely agree with most of what's been said but I still feel uneasy about the idea of binning (or most likely stashing in a drawer) most of a quite new RTR model... even if the result is easier/better/cheaper etc. Maybe it's just a hangup that I have. The answer is often 'sell the rest of it on eBay'... I just dont seem to ever get around to doing that.

 

Personally I'd prefer an option for arriving at a diesel/electric loco or MU chassis where I can have some design input and choose things like whether to mount the motor low or high, flywheels and so on. The sticking points for me have been (as Chris said) the cost of buying so many gears and also figuring out how to arrange things like prop shaft bearings and bogie pivots to hold all of those drive train bits in the correct place in three dimensions.

 

Cannibalising old locos for gears does seem like a solution to keep the cost of the drive train down. If I'm designing a custom chassis then desigining it around the available gears in my own junk box is not a big issue. Transferring the drive to the axles may be more of a problem unless the gears happen to be from a Farish loco.

 

I've done my share of 3d printing (or rather Shapeways etc. have done it for me) but it seems to me that designing something as complex as a diesel chassis seems likely to require multiple iterations of test prints.

 

Sorry, not a lot of positive ideas here... I would like to have some... I just don't have many on this topic

[Chris Higgs]

1 hour ago, justin1985 said:

 

I'll never deny my ignorance in mechanical matters! 

 

Where is the weight carried from chassis to bogie in the first design? Is it through the whole rectangular surface of the top of the bogie, if its not through the worm/gear interface? I've never fiddled with a commercial chassis with this question in mind, but I seem to recall the bogies seeming to have quite a lot of free movement in all directions about the interface with the worm? The clips in the circular hole clearly don't carry any of the weight, they just guide the movement. 

 

I was half wondering about using spare gears sold for Farish, which seem pretty standard and not too hard to get hold of - its the worm/worm gear that seems a puzzle to source.

 

Justin

 

 

As mentioned in other replies the clips bear the weight, looking at a Dapol Hymek on my bench the clips are high up next to the worm and also have curved bearing surfaces on top. So any rotation there is which is considerable is all around the plane of the worm, hence preserving the meshing (in theory at least).

 

There are alternatives available from a number of American prototypes, and often better engineered than UK outline models. These used also to be very cheap, once again not so much any more. A GP-40 is pretty much correct wheelbase and bogie centres for a BR Class 24/25, and an RS-3 with vcentre wheels removed for CLass 26/27/33. 

 

Worms for Dapol locos are often available at DCC Supplies. And bogies are also available, sometimes at quite keen prices. Hymek bogies at 8.50 each at the moment.

 

Chris

 

Chris

[justin1985]

Many thanks all - great ideas here - and I think I've got a much clearer idea of how the gearing works now!

 

1 hour ago, Izzy said:

You will see on my Priory Road thread I have currently bodged up a bogie with a small coreless motor hung on it for my current 2-car 309 build. Doing this has overcome the bogie shift issue and trying to produce a plug-in type. The gear ratio is just 15-1, which is all most Farish diesels/DMU/EMU’s use and which seems to be quite adequate.

 

 

I remembered you'd come up with a custom power bogie for a Priory Road project @Izzy - I'd forgotten you'd done two different approaches! The power bogie definitely looks really promising, especially, as you say, with a good quality DCC decoder.

 

A ready made combined bogie carcass, essentially to Izzy's design, seems like it could be a relatively simple candidate for 3D printing. Obviously it would require iteration and tweaking for tolerances, so Shapeways would definitely be a terrible idea for this reason. However a home Photon type printers should be suitable. 

 

I had a quick look at Micro Antriebe and they seem to offer acetal versions of their M0.4 gears in appropriate sizes for around £4 each, which doesn't seem outrageous (although I'm sure it would indeed add up - it looks like the Farish cl.33 bogie has 6 gears each). Although didn't the Association seem to have some sort of falling out with Micro Antriebe? I seem to recall that they're no longer the source of Association gears for some reason?

 

Personally I did manage to get two of the Farish 101 power twins back when they were in the bargain-bucket, which should sort me out for the four sets of Worsley etches for GE section EMUs that I have, should I ever actually get around to building a 1990s era project (which would be in Finetrax N - but far too many other things on the go already now!). 

 

What got me thinking about other solutions was discussing @Lacathedrale 's Caterham idea, which would need inter-war Southern EMUs - and seems like a really nice plan! But as we've all noticed, Farish DMUs and even US Bachmann diesels (I did think and look - most now in the £110 region) are no longer bargain bucket material, which makes chopping them up not seem quite as obvious as it used to! 

 

Justin

[D869]

22 minutes ago, Chris Higgs said:

 

There are alternatives available from a number of American prototypes, and often better engineered than UK outline models. These used also to be very cheap, once again not so much any more. A GP-40 is pretty much correct wheelbase and bogie centres for a BR Class 24/25, and an RS-3 with vcentre wheels removed for CLass 26/27/33. 

 

 

Indeed. I've been down that route. An MP15DC is a good match wheelbase-wise for a class 22 and the Atlas chassis runs very well. Sideframe detail is a challenge because it looks very non-British and the sideframe is needed to hold the bearings/pickups in place. I've approached this on both the class 22 and the Kato DMU chassis by butchering the overseas chassis detail. Finding a suitable wheel diameter can also be an issue with US chassis and most 6 wheel US bogies have non-equal wheel spacing to fit around the traction motors.

 

I even invested in a US book of diesel loco drawings so that I could find the key dimensions when I need them.

 

I have thought about how I might build a 'see through' class 22 bogie with spoked wheels and without a chunky gear train to spoil the view... and then thought I'd go and do something less difficult instead.

[D869]

17 hours ago, justin1985 said:

I had a quick look at Micro Antriebe and they seem to offer acetal versions of their M0.4 gears in appropriate sizes for around £4 each, which doesn't seem outrageous (although I'm sure it would indeed add up - it looks like the Farish cl.33 bogie has 6 gears each). Although didn't the Association seem to have some sort of falling out with Micro Antriebe? I seem to recall that they're no longer the source of Association gears for some reason?

 

 

I was having another look at the gear question. My notes of past research say that Farish locos have 0.3 mod gears... which ties in with what Julia said too so if you want to have the option of using the Association drop-in wheels then 0.3 mod seems like the thing to have. My notes also say 0.3 mod for my Dapol Hymek which is one of the early ones so things may have changed.

 

I haven't found anything that beats the prices from the 2mm shop. If I understand correctly the gears are now being done in house. Whether the in house person has the capacity if we all start building diesel bogie spur gear trains with 2mmSA gears is another question.

[Chris Higgs]

2 hours ago, D869 said:

 

 

I haven't found anything that beats the prices from the 2mm shop. If I understand correctly the gears are now being done in house. Whether the in house person has the capacity if we all start building diesel bogie spur gear trains with 2mmSA gears is another question.

 

As he does a number of other things you also all like to buy I would suggest not. But my opinion is that a gear train made up of brass gears is going to sound pretty noisy. And I would suggest rapidly approaching the price of the RTR diesels you are trying to avoid cannibalising.

 

There has been a lot of discussion on diesel chassis in the past and I cannot recall seeing many real models emerge from it, so I suspect the man in question is not quaking in his boots at any impending deluge of demand ...

 

Chris

[D869]

56 minutes ago, Chris Higgs said:

 

As he does a number of other things you also all like to buy I would suggest not. But my opinion is that a gear train made up of brass gears is going to sound pretty noisy. And I would suggest rapidly approaching the price of the RTR diesels you are trying to avoid cannibalising.

 

There has been a lot of discussion on diesel chassis in the past and I cannot recall seeing many real models emerge from it, so I suspect the man in question is not quaking in his boots at any impending deluge of demand ...

 

There are probably two questions getting mixed up here - one is how to motorise an MU... which may involve cannibalising an RTR thing or creating something to make life easier, perhaps 3d printed as discussed or something etched along the lines of things that have gone before such as Mike Bryant's offering or TPM's kit that cannibalised a US Bachman A/B unit to get two for the price of one(ish).

 

The other question is how to build a custom diesel chassis where the reason for doing so may be the absence of something suitable to cannibalise or a feeling that the RTR option doesn't run well enough or won't last long enough to put underneath something that we may be investing a lot of time in.

 

I've got as far as doing a CAD drawing of the drive train in one case but on that occasion figuring out how to hold the (ball race) worm bearings and arrange a bogie pivot with something that I could make myself was as far as I got.

 

I agree that brass gears will be noisy but so far the plastic ones that I've found cost more than the brass ones from the Association. I never minded the sound of metal geared Farish or Minitrix drive trains in the past and so far I have never had a split gear with those... but quiet and plastic is probably a better option nowadays if it can be achieved without being too costly.

[Izzy]

Another factor might be that you'd need 0.3mod worms to mesh with the gears.......so unless you could source some Farish ones.  BR lines does quite a few bits including a few complete older type Chinese bogies and the new/re-vamped website means easy ordering but.......costs do mount up if that's a factor you need to take into account.

 

Izzy

[MisterT]

Hi All,

 

I am coming back to the Dapol 57xx Pannier conversion, and I have a couple of questions about quartering and gearing.
Apologies in advance if these questions have already been covered elsewhere and I haven't looked in the right place.

 

Quartering
I have invested in the Association Quartering Tool, and I was planning to use this to quarter the wheels, with a tight "interference" fit in the muffs.
However, seeing as all three sets of wheels are on geared axles, if I use this approach then it seems very difficult to achieve perfect alignment over all three wheelsets. It almost seems like I would need to create some kind of jig to hold all three wheelsets in alignment.
Has anyone else who has done this conversion used the Quartering Tool, and a tight "interference" fit in the muffs, and if so, how did you overcome this difficulty?

 

Gearing
Obviously one possible way to address the difficulty in quartering is to remove the gearing on the two outside axles, so that only the centre axle is geared.
I have tested the loco with the original N-gauge wheels and coupling rods and only the centre axle geared, and it seems to run quite happily.
And of course, this is the approach that I have seen used in most 2mm scale loco builds.
So, I suppose my question is: is it a viable approach to only have the centre axle geared? am I losing anything by removing the gearing on the two outside axles?

 

Any advice would be appreciated,
Thanks,
Ed

 

[D869]

49 minutes ago, MisterT said:

Hi All,

 

I am coming back to the Dapol 57xx Pannier conversion, and I have a couple of questions about quartering and gearing.
Apologies in advance if these questions have already been covered elsewhere and I haven't looked in the right place.

 

I'm not sure how you would get the quartering 'in sync' with 3 axle gears. if your axles fit the bearings well and the crankpins fit the rods well then having a gear on just one axle is the usual approach.

 

RTR models with fully geared wheels usually have tons of play around the crankpins which may be an option... but once you open the holes out you can't close them up again so I'd treat this as a last resort.

 

I've usually had to tweak the quartering a little after using the quartering tool. It's still worth using because it presses the wheels into the muffs squarely but don't assume that the quartering will be perfect.

[Caley Jim]

If the axles are all geared, then the rods are only going along for the ride and not actually doing anything, so precise quartering is not such an issue. In fact I would guess that a bit of slop in the rod holes is desirable.  I'm open to correction on this as I've never done that.

[Chris Higgs]

5 hours ago, Izzy said:

Another factor might be that you'd need 0.3mod worms to mesh with the gears.......so unless you could source some Farish ones.  BR lines does quite a few bits including a few complete older type Chinese bogies and the new/re-vamped website means easy ordering but.......costs do mount up if that's a factor you need to take into account.

 

Izzy

 

There are Dapol worms on the site of DCC Supplies, I 'm willing to bet they are MOD 0.3 given that that all of Dapol's gears seems to be.

[D869]

30 minutes ago, Chris Higgs said:

 

There are Dapol worms on the site of DCC Supplies, I 'm willing to bet they are MOD 0.3 given that that all of Dapol's gears seems to be.

 

I'm not so sure. My (early) Hymek notes say that the wormwheel is 5.8mm OD and has 20T. This doesnt work out to a whole mod number but maybe that is the 'fudge' to allow it to pivot.

 

The spur train in the bogie works out to mod 0.3 from my measurements - the wormwheel moulding is a compound gear giving reduction between the wormwheel and the spur train.

[Izzy]

24 minutes ago, D869 said:

 

I'm not so sure. My (early) Hymek notes say that the wormwheel is 5.8mm OD and has 20T. This doesnt work out to a whole mod number but maybe that is the 'fudge' to allow it to pivot.

No, the tooth pitch must remain identical otherwise there would be run-out - compound error - between the worm and wheel as with any two gears of differing pitch. The measurements indicate the gear size to be 0.25mod/96dp.

 

Izzy

[Chris Higgs]

10 hours ago, Izzy said:

No, the tooth pitch must remain identical otherwise there would be run-out - compound error - between the worm and wheel as with any two gears of differing pitch. The measurements indicate the gear size to be 0.25mod/96dp.

 

Izzy

 

Hmm, well we used to have both 13T and 14T gears in our Imperial spur gear range which had the same O/D, so a certain amount of fudge is possible if you know what you are doing (and Bill Blackburn certainly did). The Dapol wormwheel doesn't look as fine as M0.25, but I could be wrong. But anyway, if you can get a worm and wheel that match from such a source and then the onward drive is M0.3 that sounds like something useable as the start of a geartrain.

 

Looking at  chassis to cannibalise, I have a Dapol Class 121 on my bench. It is massively over-powered for a single-car unit with all axle drive, and I am looking to take the drive from one end and put it into a dummy unit I also have to produce two powered models. I am coming to feel its half low level drive is a lesser evil than the big grey block that Farish provide in the Class 108 and 101. And it has the correct wheelbase for the longer BR DMUs and EMUs. The 121 is fiddly to take apart though, with wiring all over the place.

 

Chris

 

[Izzy]

3 hours ago, Chris Higgs said:

 

Hmm, well we used to have both 13T and 14T gears in our Imperial spur gear range which had the same O/D, so a certain amount of fudge is possible if you know what you are doing (and Bill Blackburn certainly did). The Dapol wormwheel doesn't look as fine as M0.25, but I could be wrong. But anyway, if you can get a worm and wheel that match from such a source and then the onward drive is M0.3 that sounds like something useable as the start of a geartrain.

 

Looking at  chassis to cannibalise, I have a Dapol Class 121 on my bench. It is massively over-powered for a single-car unit with all axle drive, and I am looking to take the drive from one end and put it into a dummy unit I also have to produce two powered models. I am coming to feel its half low level drive is a lesser evil than the big grey block that Farish provide in the Class 108 and 101. And it has the correct wheelbase for the longer BR DMUs and EMUs. The 121 is fiddly to take apart though, with wiring all over the place.

 

Chris

 

 

I agree, you do need to know  what compromises and restrictions arise from departing from the norm, e.g. certain BA bolt sizes mesh okay with gear threads for easily made worms within the restriction of critical meshing distance. Indeed any thread tap can make a useful hobbing tool to produce simple one-off worm sets within the constraints imposed by their use, (so long as you have a decent geared hobbing setup), it's all fun and games....

 

Do I understand it correctly that the Dapol 121 has a better drive system than the 153/156? Sounds very useful. Dapol spaghetti wiring.....I know it well......

 

Izzy

 

 

[Chris Higgs]

1 hour ago, Izzy said:

 

I agree, you do need to know  what compromises and restrictions arise from departing from the norm, e.g. certain BA bolt sizes mesh okay with gear threads for easily made worms within the restriction of critical meshing distance. Indeed any thread tap can make a useful hobbing tool to produce simple one-off worm sets within the constraints imposed by their use, (so long as you have a decent geared hobbing setup), it's all fun and games....

 

Do I understand it correctly that the Dapol 121 has a better drive system than the 153/156? Sounds very useful. Dapol spaghetti wiring.....I know it well......

 

Izzy

 

 

 

I don't have a 153 or 156 so cannot compare. It's a 8 wheel drive with the motor centrally placed but lower than in a diesel. The link shows the 121 chassis, but you cannot see all the construction details. 

 

https://www.dccsupplies.com/item-p-114279/n-gauge-121-complete-chassis-2d-009-006.htm

 

Chris

[Izzy]

Thanks Chris, that certainly looks a far better design, and with better wiring on the whole by the looks of it. The 153/156 have the 'super creep' motor type with the motor and drive at/below floor level. Because of the width of the motor when laid flat the whole underframe is just a wide block with a bit of relief detail on the side. If you can as you say swap bogies about to get two power units from one 121 chassis with just another motor it seems quite economical and beneficial.

 

Izzy