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Etched loco chassis




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#26 richbrummitt

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Posted 28 June 2011 - 11:46

It probably preaching perfection, but it is better "accepted" practice in any gear mechanism to have a finer pitch to the spur gears after a worm gear, finer pitch, or the same as the pitch for the worm.


As a mechanical engineer I agree. As a 2FS modeller it doesn't matter, in the same way a number of us make our axle holes about 6% oversize as an incredibly crude form of making the chassis flexible to improve pick up.

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#27 Chris Higgs

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Posted 28 June 2011 - 12:39

On another note is the 2251 chassis really a substitute for a dean goods? I think I remember being told the N brass kit has been 'adapted' to fit the 4F chassis, in which case the splashers may need moving.


Oh well. My interest just plumetted from low to zero. However the 2251 chassis is the correct wheelbase for a 'proper' Dean Goods, although if there was any mileage in it, I'd be likely to produce a different chassis as the frames are a lot lighter on the Dean, just as they are on a 57XX compared to a 94XX.

#28 Chris Higgs

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Posted 28 June 2011 - 12:42

As a mechanical engineer I agree. As a 2FS modeller it doesn't matter, in the same way a number of us make our axle holes about 6% oversize as an incredibly crude form of making the chassis flexible to improve pick up.


Never fear. I have discovered that the 2251 chassis could also be built with other combinations of spur gears which have near enough the same centres.

20:28 using M0.3
20:37 using 100DP -altohough you diefinately want the 10.5mm dirvers in this case

Chris

#29 SteveBedding

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Posted 28 June 2011 - 16:12

Just for reference, both the Dean Goods and the Collett 2251 used 5' 2" 16-spoke driving wheels on 7'3" - 8'3" spacings; this diameter equates to 10.36mm at 2mm/ft, which is closer to the 10.5mm association drivers.

The only real difference (that would be noticeable in 2mm) would be the front and rear 'over-hangs' which were 4'9" & 4'0 for the Dean and 6'6" & 4'9" for the 2251. If the chassis was sized for the 2251, it would be a matter of fettling about 3.5mm off the front and 1.5mm from the rear...

I don't have any dimensions for the positioning of the front guard irons, but looking at the pictures and diagrams in Russell's Pictorial Record of Great Western Engines, I would consider that, relative to the leading drivers, the locations of the guard irons are not too far dissimilar for both locos. (OK, the purists may wince at this, but it could be a pragmatic compromise...).

Posted Image

Posted Image

#30 Chris Higgs

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Posted 28 June 2011 - 16:52

Just for reference, both the Dean Goods and the Collett 2251 used 5' 2" 16-spoke driving wheels on 7'3" - 8'3" spacings; this diameter equates to 10.36mm at 2mm/ft, which is closer to the 10.5mm association drivers.

...

The only real difference (that would be noticeable in 2mm) would be the front and rear 'over-hangs' which were 4'9" & 4'0 for the Dean and 6'6" & 4'9" for the 2251. If the chassis was sized for the 2251, it would be a matter of fettling about 3.5mm off the front and 1.5mm from the rear...


Actually the 2251 body is to 1:148, so the scale driving wheel diamater would be 10.64mm. But rounding up is a dangerous thing here. The O/D over the flange will then be 11.5mm, definitely more than the prorotype, and whether that will fit inside the splashers I do not know (not owning the aorementioned loco). At some point, the AGM if not before, my chassi ethc has to be matched to the body to see whether everything has worked out as expected

Hacking 1.5 from the rear of the etch will impinge upon the rear spacer, which has specifically been positioned to match the Peco location hole. So really not quite as easy as it sounds.
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#31 SteveBedding

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Posted 28 June 2011 - 17:15

Actually the 2251 body is to 1:148, so the scale driving wheel diamater would be 10.64mm. But rounding up is a dangerous thing here. The O/D over the flange will then be 11.5mm, definitely more than the prorotype, and whether that will fit inside the splashers I do not know (not owning the aorementioned loco).

Good points Chris - I always quite happy to have my assumptions shot down... If it's any help, I've just quickly disassembled a Peco Collett and the wheels appear to be 10.7mm with a flange O/D of just over 11.8mm.

Hacking 1.5 from the rear of the etch will impinge upon the rear spacer, which has specifically been positioned to match the Peco location hole. So really not quite as easy as it sounds.

Nothing is ever as easy as I would hope it to be... :rolleyes:

#32 Chris Higgs

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Posted 28 June 2011 - 19:40

Good points Chris - I always quite happy to have my assumptions shot down... If it's any help, I've just quickly disassembled a Peco Collett and the wheels appear to be 10.7mm with a flange O/D of just over 11.8mm.


In which case, looks like the 10.5mm wheels will work. Which is nice, as the 10mm ones would have looked a tiny bit undersized.
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#33 miltwo

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Posted 29 June 2011 - 17:14

Hi Chris, the chassis looks good.

Re the wires - I have for some considerable time used wire from pick up arms of old record players (remember those?) for electrical contact between loco and tender. It's multi strand and measures .65mm diameter. Soldered as far as possible into the chassis, be it loco or tender, there is less likelihood of the soldered joint break due to flexing.

Mick S

#34 Chris Higgs

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Posted 05 July 2011 - 13:30

As an update, it has been decided to release the chassis range as Association shop items, the first of which will be the 57XX, 14XX and Class 03.

Watch the shop notes and the Association website for more news in due course.

Chris
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#35 Chris Higgs

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Posted 08 August 2011 - 18:08

Here is the next chassis, for the Bachmann BR 03 and 04 shunters. Both this and the Class 08 are now ready for production.

Chris

DSCF6645.JPG

DSCF6650.JPG

#36 Chris Higgs

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Posted 08 August 2011 - 18:17

And here are some shots of the Class 08 chassis. This has a three stage reduction giving a total of 50:1, driving onto centre or rear axle (or both). It can also be built with a two stage reduction onto the rear axle of 39:1.

I was hoping that the use of the etched outside frames (not shown) would be optional, but it turns out the Association extended axles do not extend far enough to cope with the massively overwidth Bachmann offerings. So the etched will have to be used, and the bonus is that will produce a much higher quality result.

Chris

DSCF6653.JPG

(actually the etched outside frame can be seen lurking top centre in the background)

DSCF6655.JPG

DSCF6656.JPG

DSCF6658.JPG

#37 nick_bastable

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Posted 08 August 2011 - 18:44

Chris is that the shops new can motor ?

#38 Chris Higgs

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Posted 08 August 2011 - 18:47

Chris is that the shops new can motor ?


Yes it is. It's the only sensible option for the Class 03, the 08 will take the 10mm Faulhaber/Maxon, although I don't mess around with those when doing test builds.

Chris

#39 iak

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Posted 09 August 2011 - 08:49

Now that is tasty!!!
Bravo Chris. :drinks:

#40 Pixie

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Posted 09 August 2011 - 10:59

Very, very nice Chris.

With these now near production, could you let the world know what gears, wheels and other bits are needed from the Association shop? I fancy stocking up before the rush. B)

Pix

#41 bogieman

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Posted 09 August 2011 - 11:18

And here are some shots of the Class 08 chassis. This has a three stage reduction giving a total of 50:1, driving onto centre or rear axle (or both). It can also be built with a two stage reduction onto the rear axle of 39:1.

I was hoping that the use of the etched outside frames (not shown) would be optional, but it turns out the Association extended axles do not extend far enough to cope with the massively overwidth Bachmann offerings. So the etched will have to be used, and the bonus is that will produce a much higher quality result.

Chris

DSCF6653.JPG

(actually the etched outside frame can be seen lurking top centre in the background)

DSCF6655.JPG

DSCF6656.JPG

DSCF6658.JPG


Chris, I know this is probably a very naive question, but if this 2mm and the chassis split (electrically) frame, where is the insulation within the gearbox?

#42 Chris Higgs

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Posted 09 August 2011 - 11:31

Chris, I know this is probably a very naive question, but if this 2mm and the chassis split (electrically) frame, where is the insulation within the gearbox?


There isn't any, as the gearbox is all attached to one frame of the loco and so is live to that side of the loco. That's why you get the cantilever gearbox affair on 2mm locos. The gears themselves are on an insulating muff with stub axles either end, so there is no connection between the two frames.

Chris

#43 Nigelcliffe

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Posted 09 August 2011 - 14:08

Very, very nice Chris.

With these now near production, could you let the world know what gears, wheels and other bits are needed from the Association shop? I fancy stocking up before the rush. B)


More haste = less speed. You'll get "out of stock" on some of the gears :( The good news is that Poland are due to ship a lot of gears to me in the next two weeks, which should mean the shop will be stocked by the time the kits get there.

- The (gear) tooth fairy.

#44 Chris Higgs

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Posted 09 August 2011 - 20:31

Here as promised are the other two chassis. The 14XX can either use the can motor shown, or an 8mm Faulhaber. Its going to need a pretty heavy boiler to counterbalance the motor at the back. The wheels are 10.5mm and do fit within the splashers, and I have to say are a bit of a contrast to what Dapol offered. I don't have any of the required 7.5mm trailing wheels to match.

DSCF6679.JPG

DSCF6680.JPG

The 57XX is shown with 9mm drivers, and although 9.5mm would be correct I think some metal would have to be removed from the splasher insides. The less refined moulding of the Farish era body shows up here, as does the complete lack of daylight under the boiler. Rear axle drive with lots of metal removed as Julia did produces a much better result, but is too advanced for the entry level chassis that this is supposed to be. The chassis can take a 10mm Faulhaber/Maxon, but it has to sit further back than the can motor to clear the gear below and the inside of the body above.

DSCF6682.JPG

DSCF6684.JPG

Chris
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#45 richbrummitt

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Posted 09 August 2011 - 20:38

Here as promised are the other two chassis. The 14XX can either use the can motor shown, or an 8mm Faulhaber. Its going to need a pretty heavy boiler to counterbalance the motor at the back. The wheels are 10.5mm and do fit within the splashers, and I have to say are a bit of a contrast to what Dapol offered. I don't have any of the required 7.5mm trailing wheels to match.


I can second the comment about weight. I used squashed up lead flashing absolutely everywhere possible in front of the rear coupled axle to readdress the balance when I had the opportunity to build a test etch of this chassis last year. I like the integration of the worm gear mounting into the chassis compared with the prototype though. This will make it much easier to build successfully imo.




#46 Kris

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Posted 09 August 2011 - 21:01

Those steamer kits will be very handy. All I need now is to find some money. Posted Image

#47 Nigelcliffe

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Posted 10 August 2011 - 07:31

Fixing lead inside the chassis of the 14xx near the front wheel (eg. a flat piece on each side, with a hole for axle/muff) would also help with counter-weight, and it keeps the weight low down, which I find helps on small locos.

- Nigel

#48 richbrummitt

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Posted 10 August 2011 - 12:12

It's pretty full all through the chassis as much as possible. See the picture below from my blog last year. A shorter motor could help too. The Faulhaber one I used is longer than Nigel Lawton's MidiMotor and is possibly longer than the can motor depicted on Chris' builds.

Posted Image

#49 bogieman

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Posted 12 August 2011 - 21:27

[quote name='Chris Higgs' timestamp='1312921882' post='460824']
Here as promised are the other two chassis. The 14XX can either use the can motor shown, or an 8mm Faulhaber. Its going to need a pretty heavy boiler to counterbalance the motor at the back. The wheels are 10.5mm and do fit within the splashers, and I have to say are a bit of a contrast to what Dapol offered. I don't have any of the required 7.5mm trailing wheels to match.

DSCF6679.JPG

DSCF6680.JPG

The 57XX is shown with 9mm drivers, and although 9.5mm would be correct I think some metal would have to be removed from the splasher insides. The less refined moulding of the Farish era body shows up here, as does the complete lack of daylight under the boiler. Rear axle drive with lots of metal removed as Julia did produces a much better result, but is too advanced for the entry level chassis that this is supposed to be. The chassis can take a 10mm Faulhaber/Maxon, but it has to sit further back than the can motor to clear the gear below and the inside of the body above.

DSCF6682.JPG

DSCF6684.JPG

Chris

#50 bogieman

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Posted 12 August 2011 - 21:29

Hi Chris

Assuming they're Dapol (i.e. N scale) how close is your etch to true 2mm scale on the wheel spacings?






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