Comet 3F Jinty Chassis Issue

[PenrithBeacon]

Ian

 

Surprised your jig did not align the bearings, the London Road Models alignment jigs are cheap and very effective. I have found the Comet frame jigs are fine for assembling the frames, but the alignment jogs set the bearings to the coupling rods. Not too certain how the Poppy chassis jig works

I have hit on much the same scheme. I always use the Comet frame alignment jigs and the LRM hornblock jigs.

 

Two things come out of this though; if using the Comet jigs then I always have to use Comet frame spacers as frame spacers from different suppliers are of slightly different width, not a lot, but enough to matter.

 

Secondly I don’t use broaches anymore for the holes in coupling rods, I use reamers. Small reamers are expensive but I find they give a better result. Broaches are good in many areas but not if I am creating a bearing which is what a hole in a coupling rod is.

 

To join coupling rods I use AGW rivets, simple to use and effective. With them there are no further issues with the LRM jigs.

 

The issues surrounding flexible locomotive chassis have driven me nuts for years but using the above techniques I seem to be at the end of the tunnel

 

Just as an edit, I looked at the Poppy product once at a show and was surprised to find that any one of the frame jigs covered just a few of the possible variations in axle pitch. You might need more than one jig if you intend to make a few models which was the reason why I decided that the Comet option was the better one, but then I already had them in my toolbox.

Edited November 28, 2018 by PenrithBeacon

[Bucoops]

CSB is reckoned to be pretty near impossible in 16.5mm as there aren't the clearances within the frames for the wires and their guides plus a gearbox.  If you use an 8mm gearbox as mentioned above you would only have 1.75mm either side within 11.5mm spaced frames.  Similar applies to pivoted beam arrangements bearing on the axles or bushes leaving the gearbox free to move, but is a bit more do-able as the pivot point (where you need a tad more width) can be worked with the gearbox alignment so as not to interfere.

 

Just an observation from someone who hasn't built anything with hornblocks - has your comment taken into account the special narrow hornblocks that High level do?

 

http://173.254.28.51/~highlev3/chris/Pages/spacesaverpage.html

 

I havea couple of kits to build that HAVE to use hornblocks so youve got me worried lol

[polybear]

I have hit on much the same scheme. I always use the Comet frame alignment jigs and the LRM hornblock jigs.

 

Two things come out of this though; if using the Comet jigs then I always have to use Comet frame spacers as frame spacers from different suppliers are of slightly different width, not a lot, but enough to matter.

 

Secondly I don’t use broaches anymore for the holes in coupling rods, I use reamers. Small reamers are expensive but I find they give a better result. Broaches are good in many areas but not if I am creating a bearing which is what a hole in a coupling rod is.

 

To join coupling rods I use AGW rivets, simple to use and effective. With them there are no further issues with the LRM jigs.

 

The issues surrounding flexible locomotive chassis have driven me nuts for years but using the above techniques I seem to be at the end of the tunnel

 

Just as an edit, I looked at the Poppy product once at a show and was surprised to find that any one of the frame jigs covered just a few of the possible variations in axle pitch. You might need more than one jig if you intend to make a few models which was the reason why I decided that the Comet option was the better one, but then I already had them in my toolbox.

 

 

There's also the Hobby Holidays Master Chassis Jig, which to my mind appears much more robust than the Avonside Jig:

 

http://www.hobbyholidays.co.uk/masterchassis1.php

[mark axlecounter]

I have hit on much the same scheme. I always use the Comet frame alignment jigs and the LRM hornblock jigs.

 

Two things come out of this though; if using the Comet jigs then I always have to use Comet frame spacers as frame spacers from different suppliers are of slightly different width, not a lot, but enough to matter.

 

Secondly I don’t use broaches anymore for the holes in coupling rods, I use reamers. Small reamers are expensive but I find they give a better result. Broaches are good in many areas but not if I am creating a bearing which is what a hole in a coupling rod is.

 

To join coupling rods I use AGW rivets, simple to use and effective. With them there are no further issues with the LRM jigs.

 

The issues surrounding flexible locomotive chassis have driven me nuts for years but using the above techniques I seem to be at the end of the tunnel

 

Just as an edit, I looked at the Poppy product once at a show and was surprised to find that any one of the frame jigs covered just a few of the possible variations in axle pitch. You might need more than one jig if you intend to make a few models which was the reason why I decided that the Comet option was the better one, but then I already had them in my toolbox.

 

I have the 0-6-0 type (the one in the 1st page of this) and I have done a comet 2-10-0 on it and a agw Austin seven and both of them went on the jig with no problems, and they are both true and square.

 

For rivet's I have never got the hang of them I make them to tight or damage the motion ( heavy handed lol) so I use brass pins from hobby craft. They come as 0.65mm x 20mm and you get around 400 in a pack.

All the motion I have built (including Geouge Stevenson valve gear) have all used the pin method.

 

Mark

[Buhar]

Just an observation from someone who hasn't built anything with hornblocks - has your comment taken into account the special narrow hornblocks that High level do?

 

http://173.254.28.51/~highlev3/chris/Pages/spacesaverpage.html

 

I havea couple of kits to build that HAVE to use hornblocks so youve got me worried lol

 

There's a fair bit of intrusion from the guides and that's without the handrail knob or whatever to hold the springy wire.  I would have a conversation with Chris at High Level, he is both knowledgeable and helpful.  I spent ages researching CSB before the penny dropped regarding the difficulties in using it with OO.  I don't think it's impossible, but it pushed me back to 3-point suspension.  In 18.83 you have much more flexibility within the frames but things are tighter outside for valve gear and splashers and so on.  In 16.5mm you can get clearances sorted outside the frames but motors nearly always have to sit above and gearboxes tend to be snug.

[Bucoops]

There's a fair bit of intrusion from the guides and that's without the handrail knob or whatever to hold the springy wire.  I would have a conversation with Chris at High Level, he is both knowledgeable and helpful.  I spent ages researching CSB before the penny dropped regarding the difficulties in using it with OO.  I don't think it's impossible, but it pushed me back to 3-point suspension.  In 18.83 you have much more flexibility within the frames but things are tighter outside for valve gear and splashers and so on.  In 16.5mm you can get clearances sorted outside the frames but motors nearly always have to sit above and gearboxes tend to be snug.

 

Thanks

[PenrithBeacon]

The Comet chassis is designed for the Comet/Brassmasters sprung hornblock system which takes up very little room inside the chassis

[ianLMS]

Quick update - As usual, superb service from Wizard and the new chassis etc and Comet hornblocks arrived yesterday.

 

Tested the replacement coupling rod on the current chassis and all worked perfectly on the rolling road. The sprung middle axle works just fine. Very little movement at the coupling rod hold the wheels fairly well in place as the outer axels are fixed.

 

The Comet hornblocks are super slim. Without measuring, I would say the Comet Sprung Hornblocks are designed to work with a Comet Chassis and Comet Gearbox. Will test later.

 

Fitting pick-ups and chip tonight. If it all works, will let you know. This exercise has now encouraged me to attempt a fully sprung chassis.........more to follow!

 

Thank you to everyone who has contributed. It has been a very interesting and useful.

 

Ian

[ianLMS]

The Comet chassis is designed for the Comet/Brassmasters sprung hornblock system which takes up very little room inside the chassis

Was writing my response at the same time you posted this. It is exaclty what I thought now I have some Comet hornblocks in the flesh to look at.

[uax6]

Any photos Ian?

 

Andy g

[ianLMS]

Will get some tonight - the photo's I have are from a few days ago before I replaced the centre hornblocks. I have now painted the body in Satin Black and Matt for the smokebox, and painted the chassis in matt black. 

 

 

 

 

[ianLMS]

So, last night I fitted the pick ups and DCC chip. Not happy with the results. I used .33mm Nickel Silver wire from Albion Alloys and it didnt like being tinned. When fitted, the solder didnt take to it properly but I perservered. I managed to programme the chip but the motor would just buzz when put under power. I know the chassis/motor etc is good as I tested on the analogue rolling road with the motor plugged in directly, so either its the pick ups or the chip. its a new DCC Concepts chip and stay-alive so I doubt its that.

 

I fitted one pair of pick ups so the wire rests on the top of the wheel and the front pick up from the usual rear rim of the wheel. There was a lot of sparking going on where the wire touched the wheel rim, but not much movement. Hardly any in fact.

 

So, over the weekend I will disconnect the chip, test the pick ups using analogue, and if it works fine, I know its an issue with the chip/stay alive. If it doesnt work, I will remove the pick ups and try again, possibly with some phospher bronze strip or brass wire.

 

Work left to do - fit brake rodding & couplings, add transfers, paint buffer beam, paint brass bits (safety valves etc), add crew/lamps/coal and then weather/varnish! Priority is to get it running first!!

 

Pics below: The last pick shows the Alan Gibson sprung hornblocks.

Edited November 30, 2018 by ianLMS

[hayfield]

Ian

 

I guess this is still the original chassis, Glad the chassis is now working well except for the issues with the chip

 

I am still on DC and whilst can see the benefits of using DCC I still get cold feet when seeing so many still with issues. When some RTR locos are made DCC ready with sockets and blanking plates, why is this system not used by loco builders ?

[KalKat]

You have checkrd for shorts in the chassis, and once the body is on as well? ?In onr of those pictures, one of the pickus looks mighty close to a sand box,

 

It's also very odd you had difficulties soldering NSilver..................

 

 

Emma

[Izzy]

 

If the motor is a Mitsumi could I suggest you try using the decoder set with the kind of Cv settings used with a coreless motor. I don’t know about the decoder type/make you have fitted ( I have never tried them), but I recently used a Mitsumi+60-1HL gearbox in a loco and found it much preferred these settings when used on DCC via a Zimo MX600. It was fine on DC, but very ‘stuttery’ on DCC on basic/default settings.

 

Izzy

[Norton961]

Just for information the Comet axleboxes were originally designed by Brassmasters for their EasyChass conversion kits ( and are still used in these). They were then also sold to Comet when they started to revise their chassis.

 

David

[Captain Kernow]

I've not used the Comet hornblocks but the thinness of them sounds interesting.

 

My preferred solution for an 0-6-0 in OO is to fit single beam compensation, with the rear driven axle fixed. That way any of the High Level gearboxes should fit.

 

This wasn't possible on the recent 14XX chassis I built for the Hattons body, so I built the whole thing rigid, with just some slight springiness on the rear pony axle.

 

If I was doing it again, which I might (!), I would install twin beam compensation and fit a SlimLiner gearbox from High Level, which was originally developed for 3mm scale.

[ianLMS]

Thank you all for the comments. The sandboxes are made from styrene so isnt causing a short. The sparks are coming from the pick up wire sitting on the wheel but its not causing the dcc to short. Will take a look today and see if i can sort it. It could be the cv settings. I reduced cv 29 by 4 to turn off dc so not sure if that has altered things. It could be start volts as it is a mitsumi motor and even on dc it didnt respond until the power was up fairly well. Will get a different motor to see if that makes a diffence.

[Barry O]

Ian

 

get rid of the nickel silver pick ups...it is very old fashioned and phosphor bronze wire is so much better (brass isn't a good substitute either). Strange that Triang used phosphor bronze strip for pick ups on my oldest loco (a Princess Elizabeth). While the loco is very different now the pick ups are still ok.

 

If the motor is buzzing changing the cvs may be the answer.  Does the motor work if you disconnect the drive train? I know Mike Edge has used these motors in some locos but not sure what he has set the DCC CVs to.

 

Baz

[Barry O]

Ian

 

I guess this is still the original chassis, Glad the chassis is now working well except for the issues with the chip

 

I am still on DC and whilst can see the benefits of using DCC I still get cold feet when seeing so many still with issues. When some RTR locos are made DCC ready with sockets and blanking plates, why is this system not used by loco builders ?

All the kit and scratchbuilt locomotives I have sound fitted for Carlisle have hard wired DCC chips.

Why? The sockets take up too much room. You can easily fit a "wander" socket if required (I do this while testing for shorts using dc etc)

 

So the answer is..if required a good builder can provide a socket and blanking plate. A good dcc chip fitter should also be able to do it successfully.

 

Baz

[Captain Kernow]

Ian,

 

You might also find it helps, if you can fit two pick ups to each wheel, or at least some of the wheels, if they'll fit.

 

For example, a wiper pick up working on the back of the wheel flange ('traditional') and perhaps a pick up acting on the upper part of the wheel. This is relatively easy where driving wheels disappear into the loco body where there's lots of space, such as under the side tanks and cab of a Jinty.

[ianLMS]

Thank you all for the ideas and guidance. I now have a few things I can do to see if I can improve on the situation. I am going to perservere with the current chassis as I am hoping I can learn along the way what I have done wrong. If I simply bin it and build another one I may not know what went wrong, and will repeat the same mistakes.

 

So, here is the latest update:

 

Stage 1 - Stripped the DCC chip out and wired the pick ups to the motor. Tested it using the DC controller and didnt work at all. So, I tested the arrangement with the gear disengaged using my DC controller. The motor turned, but it still didnt run as it should so the pick-ups are definately part of the issue, along with resistance somewhere in the chassis/wheels/coupling rod. Also of note, the orange wire from the chip came off without any pulling, so it must have had a weak joint on the chip.

 

Stage 2 - I stripped off the pick-ups, I tested the chassis with the motor wired directly to the DC controller. The motor ran fine with the gear disengaged, but not so when engaged. When turning the wheels by hand I could feel that it was binding in places so I stripped the connecting roads, re-fixed the wheels and made sure everything was lined up - re-tested and it worked ok still with the motor wired directly. 

 

Stage 3 - Re-fitted pick-ups using phospher bronze strip as wipers on the rear of each wheel. It was shorting between the rear of the strip and the chassis so put some insulating tape on the back of the strip and that seemd to have cured it. Re-wired the pick-ups the motor and tested again. It takes a little nudging and pushing to get it to run, but once it gets going, it seems fine. Chassis seems to waddle a fair bit though which could be a bi-product of opening up the connecting rod holes too large to limit binding, or the chassis isnt square - either way, its probably causing a wheel to momentarily lift off the track and lose connectivity. 

 

Conclusion - I am still not happy with the DC running. Its not as smooth as it should be and I am reluctant to fit the DCC chip until I am happy with how it runs on DC.

 

Options:

1. Add more pick-ups - 2 per wheel as suggested (I have .30mm phospher bronze wire on order)

2. Strip down and replace with new chassis (have new chassis from Comet) which hopeully will be square!

3. Try a different motor (Mashima 1620 / Canon 1620) - ordered a Mashima to be here on Friday which I will need for another kit anyway - if the motor is inferior it wont respond well to DC or DCC regardless.

4. Fit a new chip - have to anyway due to orange wire coming off - all recommendations of type gratefully recieved (have another DCC Concepts one and a gaugmaster one in hand)

 

If anyone has any other ideas or suggestions, please let me know.

 

I am frustrated, but i'm enjoying the challenge, and all comments are appreciated!

 

Ian

[Barry Ten]

0.45mm Phosphor bronze wire pickups for me, although I have used brass successfully in the past. I solder them to pickup pads on the underneath of the chassis and put two bends in them, one about a third of the way along, and a second two third of the way along - basically the Tony Wright method. Once I adopted this approach I found I never had any difficulty with pickups again, so any running issues can (usually) be suspected of being due to something else.

 

A good clue that pickups aren't quite right is that wheel which isn't picking up well will accrue dirt faster than the others. Worth cleaning the wheels, then giving the loco a run for a few minutes, then examining the wheel treads. Any wheel that isn't still spotless will be indicative of a pickup issue.

[Michael Edge]

Phosphor bronze strip is very difficult to use as it only bends in one plane, wire (easily available now) is what you want. With pickups on the wheel backs you have to ensure that the backs are really clean - I run them round and hold a scalpel blade on the back. Pickups on the wheel treads collect dirt very quickly, pickups on the edge of the flange never work very well probably because of the very small contact area. They usually produce a fair bit of arcing.

[hayfield]

Ian

 

I sorted out a friends chassis which was much the same even with Markit wheels

 

We stripped the chassis down to taking out the wheel bearings, there were re-fitted using London Road Models hornblock alignment jigs (rods) with the coupling rods. The bearings were soldered in place then tested so the axles rotated freely

 

Next the wheels and coupling rods were fitted, again testing the rolling chassis on a slight incline so it rolls freely without any binding

 

Check the gear meshing next with an axle in the motor mount before going to the next stage

 

Now fitt the motor and gears then test again 

 

Finally fitting pickups

 

The approach I tried teaching my friend was to test at every stage and not to move on till 100% with stage. I am just building a Branchlines 0 16.5 chassis and initially the meshing was awful, far too tight, had I not tested it prior to fitting I might have wasted hours