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Dean Goods take 3

Brassey

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As mentioned in the previous blog, the next project is to try out a sprung chassis. This is partly due to my objective of achieving optimum running. This is the Comet chassis with their hornblocks and springs that I've had in the kit pile for years. It requires a massive leap of faith that the rods will line up with the wheelbase as there is no means of adjusting this unlike with soldered in hornblocks, such as High Level, that I used on the previous 2 Dean Goods. Despite this, I set the chassis up in my jig as usual and have used the latest dodge of Romford wheels on P4 axles to check things. These wheels are undersize but do the job. So far so good. The rear retainers needed quite a lot of fettling otherwise they were too tight to allow the rear hornblocks to move.

 

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This loco will have "dummy" inside motion as sold by Brassmasters for their Martin Finney kits. The body work will be mainly leftovers from my Martin Finney Dean Goods kit that I acquired with full working inside motion. I cheated with the Comet chassis by soldering a MF EM gauge front spacer to the front which include the means to attach the inside motion. The eagle-eyed will spot that I have included the front compensation beam and rear holes for beams in case I am not satisfied with the springing and need to revert to compensation. Here are the etches you get. The wires lying around are not included.

 

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Here is the front cylinder block and slide bars with bracket to attach to chassis

 

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And made up. There are some rather small detailing parts that have been added to this that I doubt will be visible once it's in the loco

 

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Here's the whole thing completely assembled and in the chassis retained by a 10BA screw.

 

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I've since added the wires for the brake hangers and the chassis is waiting for the paint shop

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I look forward to further instalments. I have a couple of Comet chassis kits waiting to be built. 57xx pannier and 28xx. I will be interested to see how yours turns out, and if the spring system works well enough to consider using. In the past I have only made compensated chassis. Scratch built, but haven't done one for quite a few years. So a bit lacking in confidence now..

 

Rob

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It is possible to adjust the length of the coupling rods to match the wheelbase, this is actually more accurate than adjusting the blocks in the chassis.

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I have built two Brassmasters locos and a Comet chassis for the Bachmann Crab using the coil sprung suspension arrangement shown on the Dean Goods chassis, with very satisfactory results. Compared with my usual fully floating compensated locos, they glide over track work imperfections very smoothly indeed.

The only issue I have found is the lack of adjustment for ride height and level which can only really be done by suitably massive and distributed ballast, if required. Also, the weight distribution is dependent on this and also the way the spring seats have been etched and, of course, variations in the springs themselves, although I think this is a bit of a hypothetical issue and doesn't affect performance.

Still it's worked for me.

Dave.

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I like the Comet chassis because they are all CAD drawn and thus the leap of faith in relying on their accuracy is smaller than the leap of faith of trying to do it myself!!

 

What I actually do is use digital calipers to carefully measure the centre to centre distance of the rods and then the hornguides (measure the minimum dimension and then the maximum before averaging them).  The hornguides are, as etched, fractionally tight anyway so a couple of strokes on the sides are required and if you have measured before hand, you can apply these to the appropriate side.

 

I find this quite effective and I would steer people to Comet chassis for their first taste of chassis building as a result (although Mousa Models have similar characteristics).

 

What I do find with the Comet approach is that their little springs can bounce out only too easily.  I have soldered them on the top of the bearing but have since designed a little carrier to work on the Comet hornblocks (something similar from http://website.rumneymodels.co.uk/miscellaneous)and use CSBs.

 

The inside motion looks fun; must have a bash at this and it is useful to know that Brassmasters sell it separately.

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On 10 January 2019 at 11:17 AM, RobMG said:

I look forward to further instalments. I have a couple of Comet chassis kits waiting to be built. 57xx pannier and 28xx. I will be interested to see how yours turns out, and if the spring system works well enough to consider using. In the past I have only made compensated chassis. Scratch built, but haven't done one for quite a few years. So a bit lacking in confidence now..

 

Rob

I have the chassis working now and my initial thoughts are that it is not as effective as compensation for my purposes.  The deflection of the hornguides is minimal resulting in quite a rigid chassis.  This shows up some differences in track levels that hitherto I was unaware of.  I will see how it gets on over time.

 

 

Edited by Brassey

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7 minutes ago, Brassey said:

The deflection of the hornguides is minimal resulting in quite a rigid chassis.

 

The springrate of the Comet spring was designed for heavier engines.

 

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