Tim V's workbench

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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Wed Jun 23, 2010 8:25 pm

The dimples are visible - undrilled in previous pictures. I am trying not to do more than Comet intend, and where I have deviated I have tried to indicate this.
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Andy W
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Re: Tim V builds a chassis

Postby Andy W » Wed Jun 23, 2010 8:48 pm

"The beauty of the system shown here is the paucity of components - leading to less room for errors to creep in!"

That's exactly what interests me in the system. I'l watch the thread with great interest.
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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Sat Jun 26, 2010 11:08 am

Just spotted the first error with the Comet chassis. There is a large hole behind the rear driver, seen here at Barry (1976).
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And shown here on a Malcolm Mitchell 45 chassis.
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How annoying, I have decided to drill this hole after I've soldered the chassis together. I have been busy preparing the spacer pieces.
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The vero board is for the DCC socket, which will be hard wired in http://euram-online.co.uk/dcc/sockets/dccsockets.htm
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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Sat Jun 26, 2010 12:01 pm

With a fine felt tip pen, I have marked where I propose to put the frame spacers, the wiggly line indicating where the DCC socket goes.
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Re: Tim V builds a chassis

Postby Tim V » Sat Jun 26, 2010 12:48 pm

Finally time to reach for the soldering iron. I've found the clamps on the 2mm site useful http://www.2mm.org.uk/mag0897/clamps.htm
Here's my version
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It's a piece of kitchen worktop. The most important part of soldering is that things do not have a chance of moving. It takes a long time to set up, but you can get the iron in and out quick.
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Re: Tim V builds a chassis

Postby Tim V » Sat Jun 26, 2010 2:03 pm

Here is the soldered up chassis, and I've tried it in position in the body. I've tried the meter on it to check for lack of continuity. Now is the time for some split axles, available from stores etc.
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Re: Tim V builds a chassis

Postby Tim V » Sun Jun 27, 2010 2:20 pm

Regrettably I note that the split axles are out of stock at stores. I see that the EM society have premade ones.

Here are mine, I am about to file the male sections into a half round shape, to ensure they don't move. Then glue it all together with Araldite Precision - the 24 hour glue.
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Re: Tim V builds a chassis

Postby Tim V » Sun Jul 04, 2010 6:58 pm

OK so the axles have been glued, and now I've been fettling the bearings into their slots. Very simple, a couple of strokes in each slot, and remove the burr with a scraper.
Check the bearings fit, then fettle the bearings, using a 1/8" reamer.
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And this file, which is an ordinary file, but I've run the edge against a bench grinder to take off the teeth. It can only cut on its sides, so I can enlarge slightly the groove in the bearing to enable it to rock so the axles can move around.
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I've also been working on the wheels, these are Ultrascale, I've filed a slot in the back of the tyre ready for a Bill Bedford/EMGS society shorting strip.
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Re: Tim V builds a chassis

Postby Tim V » Sun Jul 04, 2010 7:08 pm

For those not familiar with shorting strips here are the EMGS on the left and the Bill Bedford on the right. The EMGS are superior in that they have little fingers, so will potentially make better contact with the axles, unfortunately, I've only got three left, so I'll have to use the BB ones.
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Re: Tim V builds a chassis

Postby Tim V » Sun Jul 04, 2010 7:15 pm

I have scraped numbers onto each bearing, to match numbers I've scraped onto the chassis. This ensures that the bearings are matched to a slot, and always go in the same way up.
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Re: Tim V builds a chassis

Postby Tim V » Sun Jul 04, 2010 7:34 pm

And here is the simple jig I've used to hold the shorting strip down onto the wheel.

A piece of 1/8" dowel from the model aircraft shop, into a handy piece of tufnol (or it could have been plywood) with a modified wooden clothes peg as a press.
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Next step is to tin the strips before soldering them to the wheels.
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Stephen F
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Re: Tim V builds a chassis

Postby Stephen F » Sun Jul 04, 2010 7:50 pm

Did you consider using silver conductive paint, Tim?
I'm planning American style picking up with Gibson wheels so am interested to see your prep here. I'm expecting to try the paint out, and was planning a slot for it in the centre boss, which I see you've removed to make space for the shorting strip.

Steve

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Re: Tim V builds a chassis

Postby Tim V » Sun Jul 04, 2010 8:24 pm

Some have tried it, I haven't, I've always got on with strips. Originally I used the wire trapped into the axle, but since the etched strips came along, I've always used those.

The bosses on the Ultrascale's have been removed to gain additional sideplay, essential on 3' radius curves, as well as provide a flat face for the shorting strips.
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Re: Tim V builds a chassis

Postby Tim V » Sun Jul 04, 2010 8:38 pm

I always try and make my chassis with removable wheels. To this end, the holes on the spring hangers have been tapped 16BA. I did this quite successfully, without breaking the tap. However, when screwing in short lengths of 16BA screw, I broke bits off. Drat. By putting a spot of oil in the hole I did the remaining 10 bits without problems.
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Re: Tim V builds a chassis

Postby Tim V » Mon Jul 05, 2010 7:03 pm

OK so I've used the jig, and here are the wheels with their shorting strips, with some I've cleaned up. One of these days we might get wheels suitable for split axle work.
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What about the spacing washers I hear you say?

AHA, the well known PECO fibre washers, the one in the foreground has had a couple of cuts, you can push these on and off axles to adjust side play. Simples!
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Re: Tim V builds a chassis

Postby essdee » Mon Jul 05, 2010 8:23 pm

Split washers - brilliant/simple; my vote for useful tip of the year, Tim!!

Keep 'em coming,

Regards
Steve

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Re: Tim V builds a chassis

Postby Tim V » Mon Jul 05, 2010 8:29 pm

Thanks Steve.

The gearbox is a High Level one, with a 10mm can motor.

It's an assembly job now, just got to press the wheels on, make up the crank pins before doing the rods.
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Re: Tim V builds a chassis

Postby Tim V » Tue Jul 06, 2010 8:28 pm

OK, a matter of moments to press the wheels on using the GW press. Make sure the bars are well oiled, that the axle end pins are flush to the face, and that there is no dirt on the jig. Ensure the crank pins aren't too long, as they'll foul in the jig.
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Just time to check for continuity, then look at the crank pins and coupling rods.
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Re: Tim V builds a chassis

Postby Tim V » Tue Jul 06, 2010 9:07 pm

Continuity OK, so I've assembled the axles into the chassis. The springs were manoeuvred onto the pips easily with a pair of tweezers. The number "2" is visible scratched onto the bearing. This should be visible ensuring the bearing can only go one way into its slot.
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Getting the pesky 16BA nuts onto the studs is frustrating, here is a picture of a small screwdriver with a blob of blue tac on the end holding the nut ready to be pushed onto the stud.
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Re: Tim V builds a chassis

Postby Tim V » Tue Jul 06, 2010 9:30 pm

A matter of a few minutes work and all axles are in place.
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And here with the body on.
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As things stand, the pickups and suspension are already done. Plain sailing from now on :!:
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Re: Tim V builds a chassis

Postby Horsetan » Tue Jul 06, 2010 10:20 pm

Going well there.
That would be an ecumenical matter.

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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Wed Jul 28, 2010 9:00 pm

Back from hols, so on with the chassis.

I have drilled the coupling rods with a very sharp 1/16" drill,to match my crank pins which measure at 1.5mm (I love this mixing of measurements).
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Re: Tim V builds a chassis

Postby Brinkly » Thu Jul 29, 2010 11:41 am

Tim V wrote:I have drilled the coupling rods with a very sharp 1/16" drill,to match my crank pins which measure at 1.5mm (I love this mixing of measurements).


Do you know it is funny that we still use mixed measuring! If I asked any of the children in the school I teach in to measure the length of a table they would do it in meters and centimetres, but ask them their height and it is always in feet and inches! :) ;)

Regards,

Nick

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Re: Tim V builds a chassis

Postby Tim V » Thu Jul 29, 2010 6:36 pm

The rods are pivoted on a pin, NOT on the crankpin.

Here I'm drilling the hole for a 0.55mm lace pin. Note that the two pieces of the rod are aligned with a cocktail stick and a clamp holds the together.
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This shows the pin pushed through a rod, through a Rizla then through the other rod, ready for soldering.
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Re: Tim V builds a chassis

Postby Tim V » Sat Jul 31, 2010 10:49 am

I made a trial fit using the front rods as supplied, and I was satisfied with the running.
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So I've soldered the pivots into the rods for the rear rods,
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assembled the rods onto the chassis and a quick try under finger power and I was again satisfied with the results .
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I put the motor in, and IT WORKS!
No fiddling. These days with computer drawn chassis and rods, the correlation is excellent. I haven't had to do the usual trick of snipping the rods - in this case.
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