Metro Vick WCG1

[cabbage]

The time has come to do the main mechanical parts of this loco... In short -the power bogies!!! Normally I would wander along to my local model shop and pick up a couple of sheets of K&S Brass and chew them to shape. This time however in keeping with the premise that a G3 loco should be cheap to build I have opted for plastic. I "know" very few plastics well -but there is one that I use everyday in my designs and this is TUFNOL. Tufnol comes in a number of "grades" and the type I normally design with is termed; "KITE". The engineering grade is termed; "WHALE". There are also "TROUT" and "CARP" grades! This stuff is dirt cheap -but P&P is a killer. 

I ordered my 3mm thick sheet over the net and my 300 x 1,200 piece will come soon. They do do smaller sheets but the P&P is the same regardless of the size of sheet -so it will not go to waste.

It does also give me a chance to play with my new toys that I got for Xmas(!!!)

regards

ralph

Whale Grade TUFNOL 3mm sheet 300 x 1,200 £12.03p

Running total £47.03p

[cabbage]

Well now that the weather has warmed up(?) I have returned to my shed (with large mugs of hot steaming tea!) I spent the morning sawing off the tufnol sheet, four 5cm x 30 cm strips with a fine tooth hacksaw. I would advise not using a jigsaw for this, as despite the fact that tufnol is a plastic it generates large amounts of dust that gets blown everywhere... After examining my strips for "squareness" and being vastly disappointed by my sawmanship -I then set up the milling machine and began work. The first job was to produce a straight edge from the strips. I started out by roughly sorting the pieces to some sort of flattish "best side" and drilling a couple of 3mm holes to lock everything into place.

The picture below is "posed" for the camera -there is no way on this Earth that my fingers would be anywhere near a working milling machine!!!



The TiN drill is not really needed for drilling tufnol -but it works very well. You have to use very sharp tools -not because the stuff is hard to cut -but because of the friction and hence heat that blunt tools generate. Heat produces melting and your drill bit rapidly clogs up and if you are not careful it physically welds and embeds itself into your work piece. The only way to remove it -is to break the work piece...

Another problem you will encounter is clamping the work piece to the mill!!! WHALE grade Tufnol is used as a bearing surface, and with the average mill being "slightly oily" the thing skids around when you are cutting it like it was alive. The best method is to clamp it against a soft piece of "sacrificial" wood (I use balsa) thus the friction between the wood and the oily metal is not as high as it would be with just the raw tufnol.

The standard method of milling tufnol is to cut from the edge to the centre -which is the reverse of milling metal. This makes the tufnol turn into dust -rather than having the mill flutes propel shards of sharp tufnol around the mill (and at the operator!) This also prevents the tufnol from cracking.



The shot above shows the first pass to produce a "true" edge. The mill is an 8mm HSS one it is going through all 4 sheets (12mm) at about 1000RPM. At this point I am still not sure whether I want to make horn blocks and guides -or simply drill 10mm holes for the bearing to sit in(?)

regards

ralph

[IanT]

I can't find the reference Ralph - but I've a feeling that I've read somewhere that the tufnol dust you are producing is not that good for you (like most things these days it seems) so you might want to wear a face mask during your tufnol 'milling' activities. 

[cabbage]

IanT,

What you are referring to are "Phenolic Compounds"... NO -they are not very good for you and YES- I am wearing a mask. This stops the dust getting into my lungs -but has the far more important job of stopping the steam from my breath fogging up my safety specs!!! The "Dust Buster" in my shed has had to be emptied twice today -normally the mill gets done with paint brush or a hand brush -but today it gets a vacuum played over it.

I have decided to simply bore holes for the axles rather than going to the trouble of building horns and guides. This will make the model cheaper and easier to build.

I have Sunday Lunch to cook -so I will not be able to get back into my shed until after "a suitable repast", (and maybe a hot water bottle comes with me to the shed!!!)

regards

ralph

[cabbage]

Well after a cold morning in the shed.... The tufnol sides of the bogies have been edged with 5mm sq pine strip and the "bonnets" similarly lined -this ensures a perfect fit during assembly / re-assembly. The ends of the bogies are currently held together via 60mm M3 nuts and bolts and a piece of wood that will be the basis for the "cowcatcher".

The initial tests with the scrap box collection of gears and so -on prove the concept will work, (deep sigh of relief!). The inline 5 pole motor drives a worm to a 60 tooth MOD1 gear. This then drives a 40 tooth MOD1 gear this transmits power to the two other 40 tooth MOD1 gears on the rear driving axles, (a so called triangle drive).





The net reduction is 45:1 which sounds rather high but the loco was never designed to move much faster than 45mph, all be it pulling carriages and wagons up a 1 in 70 incline... Also there is my own personal vanity at stake, after having taking all the time and trouble to produce a genuine scotch yoke assembly it would seem to be a waste of time if people cannot see it working(!)

regards

ralph

12Volt 5 pole motor @ £2 each £4.00p

Running total £51.03p

[cabbage]

The shot below shows one of the "bonnets" with its motor installed.



The next problem is actually one of dynamics.... The IDEAL pivot point is directly in line with the end of "bonnet" closest to the body of the loco. HOWEVER the weight of the motor will make the cornering slightly "sluggish" -so some thought will have to be done (and a few scribblings) to get the point of balance of the bogie to sit directly under the bellows joint between the bonnet and the bodywork. This can only really be done when I have the completed bogie and wheels etc assembled. So, the next step after the gears arrive, I haven't got an invoice yet from Technobots yet -so I can't tot up the running total, is to make some wheels.

I am not very good at making wheels -let me be the first to admit!!! What I have decided to do is order some "slices" of steel rod and then lathe them to shape. After having done this and produced the raw blank the problem then is -do I cut spokes on them? Using the rotary table and my small mill it is possible to cut spokes in a radial manner and then machine out the waste to give the correct look. Something to think and doodle about in the lazy Sunday afternoon....

regards

ralph

[cabbage]

Well the nice people at Technobots have dispatched my order, and this is what I bought.

4600-138              MOD 1 40T Plastic Gear           6         £8.16
4600-141              MOD 1 60T Plastic Gear           2         £2.94
4604-012              Metal Shaft 4x150mm Pk         1         £1.49
4601-002              Plastic Sprocket 16T                10       £1.52
4601-006              Plastic Sprocket Chain 1m        1        £4.75
4600-037              Standard MOD 1 Worm Gear    3         £2.19

Total:                                                                          £27.68

Running total £78.71p

The question is now -how much more do I have to buy and how much more do I have to build? Because it is starting to get "close"... I am now fairly confident that I can build the loco for under the £200 mark.

Excuse me I have to get back to work!!!

regards

ralph

[cabbage]

The gears have arrived and I have had the chance to "play" with them. Everything fits as it should -but I am looking at the 3mm thickness of the Tufnol and I feel that this is just too thin to take the bearing load of the loco. So, what I will do is make some washers and bond those either side of the hole in the chassis rail and insert a length of brass tube to take the wear. This will give me 9mm thickness of tufnol and a steel to brass bearing surface -which should be more than adequate(!)



The power take off chain and sprocket will be on the central axle, (the one on the far right of the picture), to the front axle, then a chain and sprocket to the "drive wheel" from the front axle. Mechanically speaking rather messy -but it will keep all the linkages aligned while the beast is in motion...



I would love to go and play in my shed and get it all working -but it is snowing madly and the last time I tried something at these temperatures my skin stuck to bed of the milling machine.

regards

ralph

[cabbage]

Such was the madness and desperation that at 8pm last night I gave in, wrapped myself as best as possible went out into my shed and started to play!!!

The next shot shows the start of the Krokodil drive axle. The 16 tooth sprocket has been drilled to 3.9mm and the shaft forced (very unwillingly!) through it... On the ends of this have been placed the drive / flywheel / cranks, (I am going to call it the Krokodil axle), that provides power to the scotch yoke and thus power to the other 6 wheels on the bogie. YES I admit that they are Mamod locomotive wheels and are (mathematically) 0.75 inches (scale) too big, but I bought a scrap bag of them several years ago, some of them have holes and are painted -the rest require "some work"...



After some epoxy the brass screw and steel nut will not move, (ever).



If you examine the drawing above then everything in the above shot should make sense. The drive chain to the front axle allows greater lateral movement, (something that splitting the chain and driving off the Krokodil axle would not). The Krokodil axle is then driven from this and everything should now move in synchronization with the large 60 tooth spur gear (he says....)

Time to start fettling the bonnets to fit to the bogies -this time somewhere nice and warm!!!

regards

ralph

[cabbage]

Now that it is (theoretically) British Summer Time and despite the fact that it is snowing outside I am now in a position to begin the final run into the bogies. I ordered my twelve 10mm slices of 55mm steel bar from Mallard Metals and I have some Webb H wheel covers to applique to them.

I had resigned myself to having to cut the wheel blanks and then mill the spokes out on a rotary table -however as I was passing the Williams Models stand I saw the H section wheel covers and these plus some 60thous PlastiKard will become my wheel spokes. I plan to simply CA the brass etches to the sheet and then cut and file the gaps.

regards

ralph

12 H section wheel covers           £12.00p
10mm wheel slices 55mm bar     £32.35p

Running total                          £123.06p

[cabbage]

After a few very squinty hours with a broach, X-Acto knives, and a set of needle files -I have the following photo. I would have posted it before but, (typically), when the camera started up I got the "please recharge" sign...



So, after having cut five of the six required for one bogie I eventually took the shot.

regards

ralph

[cabbage]

I will confess that I think the battery pack in my camera has expired... However at the end of a couple of hours work I faced off the "best sides" for my wheel blanks and then started boring the holes for the axles. The shot below shows the slocomb biting into the wheel blank.



This evening work will consist of finishing all the drilling work and to start marking/cutting the flanges.

regards

ralph

[IanT]

Excellent - a bit of lathework on the Forum Cabbage.

I always enjoy seeing a bit of swarf flying around, although my workshop activities yesterday were less successful. Having managed to machine and mount a new backplate to a suprisingly (for me) good fit, I was in the process of drilling the holes for the chuck when the backplate shifted on the angle plate. The first hole doesn't quite line-up. I know it can be rectified but I was not a happy Bunny last night.

Oh, and for our younger readers out there, a 'Slocombe' Drill is also called a 'Centre' Drill and Cabbage is demonstrating good engineering practice by starting/locating his axle hole with one before using a conventional drill. Stops the drill wandering off-centre.

I did use a centre drill to start my hole yesterday, but it's to no avail if the work shifts....   

[cabbage]

I have been busy... The following shot shows the mill drilling the offset holes for the wheels. The hole in the Mamod wheel is used as a guide for the drill. The Mamod wheel is bolted through the 3mm hole of the wheel blank.



This shot shows the now 8mm thick blank with a section lathed out of it. The spokes inlay sits in a slightly larger hole to allow for the oozing of the epoxy. The crank pin will have to sit between the spokes so once the epoxy has set I will drop an end mill down the crank hole to bore through the ABS/Brass inlay.



Soon we might have something in motion(!)

regards

ralph

[cabbage]

Well after a "slight problem with returning home"... I can now get back into my shed and catch up on what should be doing -building locos!!! I have lathed to shape all 12 of my blanks -something that is totally boring but I did use some of the suggestions from IanT on the use of collets. This involved unshipping the 3 jaw and fitting the EM32 collet chuck to my lathe and then faffing around with a crowsfoot spanner and a bar to grip the mandrel. I now have a slight case of "spanner rash" when the crowsfoot slipped and I bashed my knuckles on the bar. Note to self -check blood sugar levels more often!!!

I now have one set of wheels nearly ready to begin the main operation of manufacturing the linkages and scotch yoke assembly. This is going to be made from scraps and offcuts of K&S brass section -so I count these as "free". It is going to be made from 1/4 inch 32 thous thick strips for the conrods and 3/4 inch 32 thous for the scotch yoke. I plan to use lengths of brass tube (4mm thick) for the crank bearings and 3mm bolts to supply the crank pins. The whole lot will have to be assembled in a jig (more plywood to set fire to!) and silver soldered together.

Tomorrow I plan to assemble the jig for the linkage -so I will post a completed picture of it. There will (of course) be no point posting an "after" picture... If the masterplan has survived its plastic sleeve from the damp of the shed then the jig will simply be a case of co-ordinate drilling (he says).

regards

ralph