Review of Kernow D600 'Warship' No. D602 'Bulldog' [K2602]

Prototype History

The Kernow D600 Warship is a model of the British Railways Class 41 diesel-hydraulic locomotives, built by the North British Locomotive Company in Glasgow during 1957 and 1958. Although they were withdrawn before TOPS was introduced, British Rail classified them as Class 41. All were named after Royal Navy vessels, hence the nameplates each bore a subtitle "Warship Class".

The fleet was ordered by the British Transport Commission as direct comparison with British Rail Class 40, and were not actually wanted by the Western Region, who preferred their production fleet of D800 Warships. The D600s were the result of power politics within the BTC and the WR: the former was unwilling to sanction radical, stressed-skin lightweight construction locomotives at the time, while the latter was equally insistent that at least some of the new Type 4 power range locomotives on order be equipped with hydraulic transmission. They were much heavier than production Warships (almost 120 tons, compared to 80 tons) and can be regarded as standard 1950s British design diesel locomotives that just happened to contain two lightweight, high-revving diesel engines coupled to hydraulic transmissions rather than one large, slow-revving diesel engine and electrical generator set. For this reason they were practically obsolete in design terms before they had left the drawing board.

D600 was officially completed on 25 November 1957 but was not handed over to BR until that December. Some trial runs with passenger coaches were done in south-west Scotland before D600 was allocated to Swindon in January 1958. A press run was arranged for 17 February 1958 when D600 hauled a 340-ton train between London Paddington and Bristol Temple Meads with stops at Reading, Didcot and Swindon.

D601 appeared in March 1958 and was also initially allocated to Swindon. By June 1958, both were based at Plymouth Laira and D602-D604 were then allocated there from new. The allocation of all five locomotives in July 1967 was Laira.

Entering service between January 1958 and January 1959, the class initially worked on the London-Plymouth-Penzance route of the Western Region. On 16 June 1958 D601 hauled the Cornish Riviera Express non-stop from Paddington to Plymouth, the first diesel locomotive to do so. The maximum permitted loads for a D600 on such a run were 375 tons (381 tonnes) westbound (climbing the 1-in-37 of Dainton Bank, west of Newton Abbot, and up Hemerdon Bank's 1-in-42 in the opposite direction). The D600s continued on the fast Bristol/West of England trains until a dozen D800 Warships had been accepted into service. Later they were largely restricted to the line west of Plymouth, finally being withdrawn en bloc in December 1967. They were noted for being capable of over 90 mph (140 km/h) if worked well and did run at 100 mph (160 km/h) during their very early careers. D603 was damaged in an accident and was returned to NBL for repair in 1960: the cast light alloy cabs were replaced with sheet steel as the original NBL subcontractor for these items was not prepared to fabricate a small, one-off order. Swindon had a spare cab which was not used and survived long after the locos had been withdrawn before finally being sold for scrap.

From new the D600s wore standard BR green with a 4-inch (102 mm) light grey horizontal band between the cabs a few inches above the solebar. By the time of withdrawal D600 was in all-over rail blue with full yellow ends, D602 was blue with small yellow warning panels on each nose and D601/3/4 were still green, albeit with yellow warning panels.

All five locomotives were withdrawn on 30 December 1967. By this time they were non-standard, even for hydraulic designs, although according to Laira staff reliability was not a problem as many have thought. BR had been ordered to reduce the number of main line locomotive classes from 28 to 15 by 1974, primarily by eliminating types which were known to be unreliable, had high maintenance costs or were so few in number as to be non-standard. As the table below shows, there was a substantial gap between delivery of D601 and D602 because NBL had to equip itself to construct the engines and transmissions for these three locomotives. By this time the first Swindon-built D800s had entered service and these were the lightweight and more powerful diesel-hydraulic locomotives that the WR really wanted.

D600 and D601 were sold to Woodham's Scrapyard in Barry. D600 was broken up within a couple of years but D601 remained intact until 1980. Preservation for D601 was denied on the grounds that it was too far gone to be restored to operational condition and was not considered to be worth preserving for display only. The last survivor of what had been Class D600 was broken up in Woodhams Scrapyard, surrounded by locos which it had been intended to replace. D602-D604 were sold to Cashmore's of Newport who broke them up far more quickly than Woodhams (who concentrated on 'quick to process' wagons before tackling locomotives). The fleet only lasted eight years in revenue-earning service. D601 actually spent more time in the scrapyard than it did hauling trains on the main line!

No Class D600 Warships survive in preservation.


The model is supplied in the standard style of box we have seen from Dapol, Hattons and Heljan. We won't be adding to the plethora of 'how to open a box' videos on YouTube, needless to say, the box is solid and protects the model very well.

Once removed from the box, the model itself looks superb. Something which was fairly quick to spot is that it is not obvious which outlets on the roof are the engine exhausts - typically, most models these days have an exhaust outlet 'hole' in the roof.
The model is a simple construction and appears solid and well made. A pack of accessory pipes are supplied for fitting and the instruction sheet shows how these are fitted. Interestingly, there is one more pipe supplied than there are holes on the front of the loco.


I test run all new locos on my workbench 'layout' before making any modifications, fitting accessories or fitting a DCC decoder.
When run on DC using a Gaugemaster DS100, this loco runs very smoothly, probably the best I have ever seen for a loco on DC control. This is obviously a result of the choice of the coreless motor. Directional lighting is provided on both ends and there are switches on the underside of the 'tanks' between the bogies. Note that these are not fuel tanks - these locos were unusual in that they had two fuel tanks (of different sizes) which were located within the bodyshell, not underslung between the bogies which was common on most other types.

Fitting a DCC Decoder

Dismantling the model is very easy: the body is a snug fit over several lugs on each side. The lower edges of the body sides just need to be prized away from the chassis and the body will come off relatively easily. Be careful when removing the body because their are two wires which attach the body to the chassis, one at each end. These run to the ends via the roof space for lighting.

Once removed, the motherboard is accessible. This model uses a 21 pin decoder socket and it is wired the correct way up. I fitted a brand new Loksound V4 decoder with the expectation that the decoder would need configuring for the motor, especially as this motor is very different to the skew-wound can motors fitted to most model locos these days.

Decoder Configuration

Most locos we come across require very little, if any, decoder CV adjustment and mostly run well 'out of the box', however, the motor in this model is so significantly different to every other RTR loco that it requires its own specialised set of configurations. Configuring a Loksound decoder for this loco is an absolute 'pig'. No matter what configuration of CV's I set, I was not able to 'tame' this loco. South West Digital made the following CV configuration publically available (also via Kernow), however, it did not work for us.

CV2 - 2
CV5 - 255
CV53 (Reference Voltage) - 100
CV54 (K) - 10
CV55 (I) - 10

We believe that CV52 is missing from this list and indeed, when adjusted, it seemed to have the most positive impact. However, we could not find a combination of settings which would stop the loco starting jerkily and stop it jerking violently as the loco came to a stop.
On two occasions, the loco stopped with flickering lights. Removal from track and replacement on track seemed to resolve this. We have heard reports of this being a problem related to a cut-out 'polyfuse' (which looks like an orange capacitor) located under the decoder. Bridging this component on Kernow's advice made no difference.
The loco constantly displayed random behavior at start-up: sometimes it would start smoothly, other times it would be jerky and there was no way to 'cause' either - it just did what it did.

It was at this point that I 'bit the bullet' and removed the motherboard, wiring in an 8 pin socket so that I could have a direct decoder/motor setup with no motherboard. This experiment proved that the motherboard wasn't the problem. I was not able to get any ESU decoders to work. I did manage to get a DCC Concepts decoder to work.

After further consultation, Kernow provided the following CV configuration which had been published by Digitrains:

CV52 (K Slow) - 1
CV53 (Reference Voltage) - 140
CV54 (K) - 28
CV55 (I) - 50

We can report that this combination seems to work well, stopping the jerking issues, however, it did not stop the random cutting out. What we found was that the loco would run for about 1 metre and then go into 'cripple' mode where it would only crawl. Reversing the loco in the opposite direction, it would run normally. Reverse again and cripple mode occurred. It seemed that cripple mode was was cutting in in one direction only. But it wasn't consistent between operating sessions!
What was noticeable was that when the loco went into cripple mode, the decoder was so hot that it caused one to remove fingers quickly. Neil from Wheeltapper sounds kindly provided the CV settings for switching on decoder protection and reducing CV53 from 18v to 14v. As a result, the decoder ran cool. But it still kept going into cripple mode and it seemed to be a bit more jerky. The problem is, this model is so inconsistent, it is really difficult to work out what really is going on!

Every sound producer we contacted confirmed that they couldn't reliably tame this loco. I have come to the conclusion that the motor in this loco is 'unfit for purpose'. It does not work with ESU decoders - a top of the line manufacturer of decoders - and it has characteristics which change randomly and completely confuse decoders. It would be interesting to know what experiences our Zimo friends have had.

The point should be made that it is not up to sound decoder and sound package suppliers to 'fix' the problems. It is up to the manufacturer to supply a model with a motor which confirms to the standards of the hobby, not the other way around.

I have spent several weeks trying to resolve this problem. In my 45 years of modelling, I have never come across a loco like this. One could easily say that maybe this is a faulty loco. Since several sound producers have had problems, it seems fairly obvious to me that this model simply has the wrong choice of motor.

At the time of writing (17/7/2019), Kernow have mailed a replacement motor. This article will be updated with the results. If that doesn't work, I'll be sourcing a Mashima-type conventional can motor to use as a replacement - something I should not have to do with a GBP 150.00 brand new loco!

Photos of the model


Fabulous looking loco, well constructed, accurately and finely finished, great performance on DC.
On DCC, this loco has a crap motor which is simply not fit for purpose. It is obviously a motor which has been developed for some industrial purpose, but it is incompatible with ESU decoders which happen to be my decoder of choice.
At this stage, we can recommend this loco to DC users, but for DCC users, we have to say 'buyer beware'.


Replacement motor has arrived from Kernow.


The replacement motor has now been fitted. The loco was run up and down my test track without any issues so I proceeded to run it on 'Ashprington Road'. Running light engine, there were no problems running up and down. It seemed that the replacement motor had improved the situation, however, the decoder became fairly hot which is unusual for just running up and down with no sound operating. Either way, the loco seemed to be running correctly.
I then coupled the loco up to an 8 coach train of Bachmann MK1 coaches. For about 0.5M, the loco ran fine, then it started lurching. This continued for a few moments until the decoder went into 'cripple mode' again.

So it seems that while the new motor may have improved the situation, it certainly hasn't fixed it.

While running light engine, there was little weight to be hauled. Once I attached 8 coaches, the dynamics of the motor under load changed the BEMF, presumably completely confusing the decoder, drawing too much current and eventually causing the decoder to protect itself and go into cripple mode.

So here is the offending 'critter':

The motor can is 25mm long and 17mm diameter. Total length across black plastic drive shaft couplings is 50mm. It isn't marked or branded in any way, so no idea who makes it. Bottom line is that the motor in this loco is utter garbage, totally unfit for purpose and has not been properly tested.


It turns out that the overheating caused by the motor has in fact damaged the decoder. A replacement LokSound V5 decoder has been obtained and fitted and the above CV settings applied. The German V200 sound pack from the ESU website has been temporarily programmed and all is working.
The only issue is that even with the above CV settings, the loco starts and stops with a jerk. Sound producers I have communicated with have indicated that this is really difficult to resolve...because the motor isn't fit for purpose.
I will be applying one of the commercial sound packages shortly.


Work and family matters have taken over for the past few months, however the Christmas period afforded some time to have a 'fiddle' with the CV settings of this loco and I finally managed to get them to a combination which I consider to give very acceptable running. I now have a usable loco - woohoo!

Before the loco returned to the layout, I decided to fit drivers in each of the cabs. I use the 'Monty's Dart Castings drivers as I believe they are the most reallistic I have come across - they look natural. The cab seating units on this model are screwed in - which is really handy, unlike the Dapol class 22 where they are glued in and virtually non-removable! Removing the cab seat units highlighted another design fault. One would have thought that if the cab seating units are screwed in that of it has wires attached to it then the unit and the lighting all come out together. But nope, on this model, one of those el-cheapo melted plastic 'globs' (really ?) is used to fix the lighting wires to the underside of the cab seating units. Some of the wires attach to the markers lights which are part of the seating unit, but other wires attach to the lights behind the head code panels and these are fixed to the body. So a nice half-and-half inconsistent design. Neadless to say, I pulled the cab seating unit out and ended up pulling the wires off the back of the head code panels on one end. Only a small soldering job to fix, but what a dumb design! On the other end, I was more careful and removed the melted plastic 'glob' unrevalled the wires first. All was then OK.

Here are a number of pictures of D602 running on Ashprington Road. These first few pictures show D602 with the 'down' 'Cornish Riviera' approaching and departing Ashprington Road:

These pictures show D602 hauling the 'up' 'Cornish Riviera' leaving Ashprington Road:

The Model in Action

D602 'Bulldog' Arrives and departs from 'Ashprington Road'

Final motor CV Settings

The video above shows the loco fitted with the Loksound 5 decoder and running with the following motor CV settings. I found these to give about the best results which can be achieved:

2Start Voltage30
5Maximum speed205
49Extended Configuration #117
51(K Slow cutoff)10
52BEMF Param (K Slow)0
53Control Reference Voltage100
54Load control Parameter K28
55Load control Parameter I240
56BEMF Influence at VMin30

Graham Plowman (Created 17/07/2019, Updated 7/08/2021 11:29:39 AM +10:00)

Locomotive supplied by:
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