Author Topic: 2-knowledge...  (Read 452 times)

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Offline cabbage

2-knowledge...
« on: Jul 12 2019 11:29 »
I have bought the plans for the Chris Barron's"2-NOL" emu. I have a feeling that the Fermi Question has arisen... Am I alone in building it?

Of the "large number" of Peak plans I only know of two completed models(?) The traction system used, I don't know either, but it will probably be a geared down 914D motor from MFA/Como Drills. If so -then my favourite electrical parts shop will get a visit!

The main idea is that this will be the first test of the carriage cutter. The machine should be able to "router" the sides out of 3mm ply and then carve balsa wood slabs to produce the ends with. However as the saying goes "No plan survives first contact with the enemy!!!"

Regards

Ralph



Offline IanT

Re: 2-knowledge...
« Reply #1 on: Jul 12 2019 12:36 »
"In physics or engineering education, a Fermi problem, Fermi quiz, Fermi question, Fermi estimate, or order estimation is an estimation problem designed to teach dimensional analysis or approximation, and such a problem is usually a back-of-the-envelope calculation. The estimation technique is named after physicist Enrico Fermi as he was known for his ability to make good approximate calculations with little or no actual data. Fermi problems typically involve making justified guesses about quantities and their variance or lower and upper bounds."

[ Thought initially Ralph was referring to a band saw or something similar - but I looked it up! ]

 ;)

IanT
Nothing's ever Easy - At least the first time around.

Offline Doddy

Re: 2-knowledge...
« Reply #2 on: Jul 12 2019 17:51 »
I have a feeling that the Fermi Question has arisen... Am I alone in building it?

Of the "large number" of Peak plans I only know of two completed models(?)

I seem to remember that 492 is building a 2-HAL.

Large number of Peaks? 23 sets had been sold when I ordered my plans four years ago.
"You don't know what you don't know"

Offline 492

Re: 2-knowledge...
« Reply #3 on: Jul 13 2019 09:10 »

Yes, I am having a 2HAL built by Peter Rogers. It has taken a long time, but is now in the final stages before completion. (We are using Tim's HP Motors to power the bogies.) The 2NOL used new SR underframes with LSWR second hand bodywork. Would be very interested to see how your 2NOL progresses using the carriage cutter.
 A very useful reference book is "Southern Electric Units Drawings and Plans" by Brian Golding. Has accurate and detailed drawing of SR EMU's, including the 2NOL.

Good luck with this interesting project.

Robert, 492.

Offline cabbage

Re: 2-knowledge...
« Reply #4 on: Jul 16 2019 12:44 »
The plans have arrived and some aspects are very puzzling(?) The motor bogie plans are "reasonable" and have a motor power each axle. However it seems to be that there is only one motor bogie per carriage? Ideally I would assume that they are at opposing ends of the emu.

My first reaction is to power each bogie but use a chain link between the axles. The infamous 11.5 mm Aluminium channel is there again. Hopefully a supplier is nearer than Poland...

It doesn't look a bad emu to build and yes some parts are going to be cut from steel rather than Aluminium as it will be easier to work with. The screws and threads are going to be all metric rather than wire numbers and BA(!)

Back to lunch and sharpen a few pencils for annotations...

Regards

Ralph

Offline Doddy

Re: 2-knowledge...
« Reply #5 on: Jul 16 2019 13:32 »
The 2-NOL has two independant designs of carriage.
  • 1 x Driving Motor Brake (DMBT)
  • 1 x Driving Trailer Car (DTC)
The blood and custard website explains the details of the construction of the two car types.

https://www.bloodandcustard.com/nol001.html

Both the DMBT and the DTC have differing bogies at each end. An 8' 9" bogie exists under the driving cabs of each carriage, and an 8' 0" trailer bogie on the two inner ends.

The 8' 9" bogies - Driven (DMBT) and Trailing (DTC) bogies were matched in wheelbase length to allow them both to use the same standard length wooden shoebeams.

Thus, the 2-NOL only has two traction motors per two car unit, both located on the same bogie, underneath the Driving Cab/Luggage area of the DMBT.

Regards,

Bob.






"You don't know what you don't know"

Offline cabbage

Re: 2-knowledge...
« Reply #6 on: Jul 16 2019 19:11 »
Robert, thank you for the information! The plans only show one type of bogie -the power bogie. So, I assume the model is supposed to run on four of these. Which does make sense from a predictability of handling point of view.

I would love to know where Chris Barron gets his 11.5mm channel from! As before the only supplier is in Poland -a glazing suplliers(?) Thus it is going to 12mm steel channel. This does improve construction in my view. It is cheaper, I can pick it off the shelves at B&Q and it is easier to work with. Prior experiments with attempting to bend 1.5mm Aluminium through 90 degrees has resulted in two pieces... But despite this -the rebent ally channel is all over the drawings(?) To be honest I will probably print the spacer pieces rather than try and bend them

When I wrote about how LBSC did his plans in the G3 Wiki I wrote that it took some time to get inside the mind of LBSC but once you had got there everything was "obvious"! The same applies here. The dimensions are all millimetre metric, the drilled hole sizes are all in Wire Numbers and the nuts and bolts are all BA... The hole sizes are really all metric viz: #54 or 1.4mm etc. All of the nuts bolts holes etc are direct metric sizes. For some reason - he never says so...

The brass bevel gear he quotes for the power bogie is a Meccano part number and the motor comes from MFA/Como Drills -all set for a 6mm shaft MOD1 gear(?)

I have come to the conclusion that he does this curious mix to present his plans as "Model" plans -rather than "Engineering" plans.

Regards

Ralph




Offline Doddy

Re: 2-knowledge...
« Reply #7 on: Jul 16 2019 19:20 »
A very useful reference book is "Southern Electric Units Drawings and Plans" by Brian Golding. Has accurate and detailed drawing of SR EMU's, including the 2NOL.

Robert, 492.

Thank you for the recommendation Robert. Ebay is delivering one this week.


"You don't know what you don't know"

Offline cabbage

Re: 2-knowledge...
« Reply #8 on: Jul 16 2019 19:36 »
Having checked the motor specified... This is an MFA 280/1 I would now have to say that each of the bogies would have to be a power bogie...

I am in town tomorrow so I will purchase my normal SME motors and draw up a suitable gearbox arrangement.

Regards

Ralph


Offline Doddy

Re: 2-knowledge...
« Reply #9 on: Jul 16 2019 19:51 »
Having checked the motor specified... This is an MFA 280/1 I would now have to say that each of the bogies would have to be a power bogie...

I am in town tomorrow so I will purchase my normal SME motors and draw up a suitable gearbox arrangement.

Regards

Ralph



And Datasheet . . .

https://www.technobotsonline.com/mfa-motor-re-280-1.html
"You don't know what you don't know"

Offline 492

Re: 2-knowledge...
« Reply #10 on: Jul 16 2019 20:50 »
The 2NOL had only one power bogey for each two car set, although of course both the power bogey and the driving trailer bogey had collector shoes. Amongst a collection of Gauge 3 Southern Railway electric units I acquired this year, that I now think were probably made for the SR for promotional reasons by Bonds (O' Euston Road), are the underframes for several EMU's. (See this coming winter's  Newsletter article.)  These are accurate to type and to scale, if any details of same are of use to you in building the 2NOL I would be pleased to help.

Robert. 492.

Offline Doddy

Re: 2-knowledge...
« Reply #11 on: Jul 18 2019 11:14 »
Well, Brian Goldings book on drawings of the Southern Electric Units turned up and I am now non the wiser.  :P :-\ :o

Brians drawings show a bogie wheelbase configuration of 8'9" + 8'0" - 8'0" + 8'0"

Then looking at the Hornby 2-BIL, it looks like the bogie wheelbase is 8'9" + 8'0" - 8'0" + 8'9" the same as in Blood and Custards 2-NOL notes.NB: Brians drawings also show most 2 car units as having a bogie wheelbase of 8'9" + 8'0" - 8'0" + 8'0" including the 2-BIL, so who is right and who is wrong?


Although the Roxey O gauge 2-NOL model looks like it has a bogie wheelbase configuration of 8'9" + 8'0" - 8'0" + 8'0"

Robert - what does your EMU subframe bogies look like?
"You don't know what you don't know"

Offline Doddy

Re: 2-knowledge...
« Reply #12 on: Jul 18 2019 12:02 »
After a bit of digging around, Mike King draws them at 8'9"

So the SEmG forum members are going for 8'9" + 8'0" -  8'0"+ 8'9" Looks like there are many errors in the Golding book.

The October 1968 MRC (Model Railway Constructor) magazine with Ray Chorleys 2-NOL drawings also state an 8' 0" bogie for the leading cab of the DTC - this is also wrong - it should be 8' 9"

Chris Knowles-Thomas added the following statement . . .

"AIUI the trailer pick up bogies on the SR "semi-fast" units, ie 2-Bil, 2-Hal & 2-Nol were all 8'-9", same as the motor bogie.  But to anticipate a follow on query they weren't motor bogies with no motors; they were much lighter in construction."
"You don't know what you don't know"

Offline cabbage

Re: 2-knowledge...
« Reply #13 on: Jul 18 2019 14:40 »
Errrmmm... Having gone through the collection of bogie plates that I have in my collection. I have two distinct sizes; 122mm and 112mm wheelbase, yes they are the last bogie plates sold by the G3S...

I am as most people know increadibly lazy.

Yesterday I bought the four SME motors that will power the 2-nol. The plans on the piano in the living room show a power bogie with a wheelbase of 120mm.

There are good design reasons for assymetric wheel spacings -however I do not really think that this applies here. I believe that making the model with all power bogies of the same axle spacing will produce a more usable emu with more predictable characteristics.

The next task for the pencil is to produce some powered and working "unpowered" bogies???

Until there is sufficient cocoa and gingernuts to aid thinking the bogies are going to be 120mm wheelbase. But I have to admit that a 120mm with a series of 108mm would look very wrong and I admit this appeals to me!!!

Regards

Ralph

Offline cabbage

Re: 2-knowledge...
« Reply #14 on: Jul 19 2019 01:12 »
Having crunched a few ginger nuts and slurped my cocoa... I class my layout as an "out and back" -thus there really needs to be a power bogie at either end. Two sets of the short bogie plates will provide the inner bogies. having decided the design parameters it is now down to using CAD to produce some drawings for MEL.

regards

ralph