Live diesel project: Polar-Deva

I discovered this funny diesel-electric prototype dated 1924 in MTVS n° 38. (Initially, I was focused on Brissoneau et Lotz diesel-electric, which are much fancier, but for a start I thought they were too difficult to build for me).



For the chassis, I wanted to start from on the shelf materials. I found that the Playmobil loc had the right wheelbase for one side. I bought two poor condition Playmobil. What I immediately saw was that the total wheelbase is quite high for such a small loc (175mm) and that I shall have some problem with curves handling. After leaving my mind wander through many Rude Goldberg devices, I finaly decided to have a flangeless drivers central axle. How I will achieve that is not yet solved though. I shall try to convince my cousin who own a lathe to do the job for me, but handling the wheels in the lathe could be somewhat of a problem; not melting the plastic center part when tooling will be an other!
I don't mind to much about motricity because the protoype was very low powered anyway.
I will tell you about my (slow) proceeding.

Interesting project. What radius will your curves have? If it's to small I think you'll get some problems with this wheelbase even with a flangeless center.

It just a try. Anyway, I have not invested a lot (around 60 euros) in this setup. If it does not work, I will switch to a shorter wheelbase prototype such as the Brissonneau et Lotz "Deux-Sévres" even if I do not succed in a very nice body. Both have the same housing facilities for the engine et other stuff. Then I would start from a ready built three axles chassis. The other material I have bought: OS engine, BLDC, etc. would be the same. I can even imagine doing both, the Polar being able to run only on long radius curve: after all in 1:1 size they do not run on short radius curves!

I do not plan yet doing a fancy body as the Brissonneau VAR which I prefer a lot to upper quoted prototype: it is just a question of building convenience. Square shaped body are a lot easier to achieve than round shape. An other advantage of the Polar is that louvres were wooden type, also easier to do than metal stamped ones.

Let's wait and see!

There is the motor element based on Playmobil chassis. I agree it is not geat modelism, but it is a step.



The wheelbases is conform to prototype within 2 mm (I cheated a little -2mm-on the longer wheelbase; it is already very long and I did not want to be unable to pass curves). The middle axle drivers are to be turned to flangeless. For the next step, I shall start the chassis in assembled and glued aluminium elements.

I am creeping along on this project! Sometimes dooing mistakes, sometimes having just a hardtime to get the material. It's amazing nowdays how difficult it is to get the simplest things: aluminium rectangular tubing,etc. Suppliers have tremendous e-catalogues but when asked they don't have the tenth in stock! For that reason I have been obliged to change at least four or five times my chassis design.
Waiting for the opportunity to have may BLDC repaired (I want to take the shaft off but did a mess inthe process of doing it), I start working on the body. It will be all wooden made.

I hope to be able of showing some pictures in the shortcoming weeks

Just reporting what has been done on the project:

These are the end sides:



and the lateral sides:




The body panels have been made of 3mm plywood decorated with red cedar on the outside and ramin on the inside. The opening have been laser cut.

I am wondering about what to make the roof of. The constarints are:

- the material must be easy to bend in shape (although quite simple cylindrical shape)
- a large cut off must be made in the middle without special tools and without misshaping the rest of it
- it must be able to be glued on the MDF supports
- it must stand the exhaust gas chimney temperature or may I do a double tubing?

All ideas or experiences are welcome.

Looks very good to me. Concerning the roof, I think you´ve got a choice between the boat-building approach of thin planks and then sanding, or a very thin wood layer or two, which are capable of bending without splitting.

What is Polar-Deva ? Most of the other internet references point back to CGT or the picture in the first post. I saw the nice postcard of the Chamonix train on your VML thread but I'm assuming that was something different.

You sure will think I am somewhat crazy choosing this unknown machine! In fact it had a short life on french metric Valmondois line (one or two years) hired from a swedish company back in 1924.

Chosing an undocumented prototype is somewhat difficult to achieve, the counterpart being no rivet-counter in a position to contest anything!

No, I am joking. In fact I was afraid of building a round shape body as the Brissonneau I intended to build. It has plenty of room inside. My biggest concern to-day being the huge wheelbase, that will oblige very long radius curves.

Thanks for answering so quickly. You are not crazy at all. The loco cries Sweden and looking at the wood you are using, so will the model. I agree about the body shape  - I've never made anything with curved bodywork that I've really liked. I'm sure you work enough flexibility into the 6 wheel chassis  - I've seen two half playmobil blocks used back to back to give a really long chassis.

Thanks for your support!

Now I am going to to try to progress on the electro-mechanical part. I will report as soon as I have achieved something worth to be shown.

I took the opportunity of this rainy week-end to deal with two problems that were puzzling me and were compulsory in progressing on the mechanical part of the project:

- taking the axle of my BLDC motor and adaptating it to the nitro motor

- turning to Playmobil wheels to flangeless.

The first point is nearly achieved and I will report when completed. I am rather proud of the second because I have no lathe and must use a "Rudy Golberg device" to do the job! Have a look at it:

1- First take the major part of the flange this way:



2 - Then take off the rest of the flange:



3- The wheel has been mounted on a vertical drill and surfaced with abrasive paper until obtaining that:



The next step is filling with epoxy the plastic part in order to remove the steam engine look of the wheels.

Excellent....There is always a way to do things!

I have gone somewhat further in the electromechanical part. Here are the first views:





Here is a view of the rotor mounting on the engine shaft:

Good, that's exactly what I was trying to achieve. So you have just put the BLDC motor directly onto the crankshaft.......

How are you going to start the OS with BLDC motor?

I hope so. Otherwise I am in trouble! The BLDC is far enough powerful as a generator; my only concern is: will it have sufficient torque to staret the OS motor?

Saint-Oblas wrote:

.... my only concern is: will it have sufficient torque to staret the OS motor?

It should do. I have tried a smaller motor ok from a 12V 8Ah battery via an esc.

I had bought an esc from RCtimer with the motor. I have no battery for the moment but I may try an old car battery charger (up to 6 amp only;maybe it is enough).
I am considering buying an RC system, but this is a lot to buy as I start. So for the moment I keep going with the loc body, the chassis and so on.
I think I will sale my OS FS 70 surpass: it is much too big to be included in a IIm loc. An OS 20 or 26 would be far enough.

To day I tried to make the louvres. It is really difficult; the result is medium, not very even, but it will have to do; I don't expect to do much better if I try again.

My second try to build my engine craddle seems to be the good one. It costed me a whole morning and a complete set of 50 Roxxon discs! I think it is difficult to do more compact. My only concern is: will the BLM have enough torque to start the OS engine. If not I am in a big trouble! Just cross fingers!



I need to connect the servo to the carb and I will be through with this part. I am presently making the diode rectifier (and the door hinges). I have bought second hand an Rc (an Optic 6)
. I only need a battery to do the tests.
The main difficulty is to squeeze everything into the small body, mainly because I wanted to keep the cabs and the luggage compartment free of mechanisms. My next main challenge will be making a muffler. I must implore my cousin in law to make some silver soldering for me, because I have nothing for brass or copper soldering.

Apart from problems in fixing my hinges, I came across problems that you, experienced modelers, have overcome for long: stuffing all the equpment in such tiny room! I made a second version of my rectifier: beautiful but still too big! No room anymore for the fan! Maybe I will use an other fan than the centrifugal one I planned: a pity it was real nice.

I am still wondering how to build a small efficient easy to do muffler.

I ordered some more equipment and hope to give more positive news within a short while.

For a change I worked on the mechanical part. The people in Jet shop in Lyon have been very kind with me testing if the BLDC engine was able to draw the OS engine. It seems to work but only with a 14.8 volts battery. The compression of this engine is pretty high and the torque to start it consequently also high. But it should work.
For size reason, I think I will abandon connectors and weld everything or nearly everything: my chassis is becoming overcrowded. This may also help because of the starting intensity which may have trouble getting through small connectors.

Some news of my project progress. I nearly through with my chassis:



I am waiting for my reception battery pack to test the servos before assembly. I think I have succeeded in packing everything in the box! with  two infractions: the equipment will overflow on one end on the driving space (but after all, I will only put one driver!); and the battery pack will be located in the luggage compartment (dissimulated in a wine wooden box).

I have tried the BLDC motor to turn the OS engine: I need a 14.8v Lipo battery, but it should work.
I must still make all the elements assembly, electric connections, body assembly and body detailing (windows, etc.) + the roof. I am glad I have not done it yet because I think I will foresee a small fan for hot air extraction.

Some news on my project.

The body is being assembled. I still keep the windows protected.



The roof is being shaped before gluing:



It is cut in 2mm plywood

That roof looks very interesting.  It looks like heat will escape easily.  Will the electric fan will be used in extractor mode?

Best wishes,
Dave.

The roof will not help in heat removal. The cut does not goes through. It is just for bending ease. It has been donne with laser. I plan to cover it with a thin sheet of metal (either tin or zinc).

Yes the fan is supposed to extract hot air from the engine compartment. There is also a smaller one directly flushing the engine head.
My only concern is their feeding from the electrical generator: they are 12 volts model and my generator will only deliver around 7V at idle. Maybe I will have to replace them with 5V model; but I chose 12V so that the regulator circuit does not overheat too much at higher engine rpm.