My Beaut Aussie Cent

[simon_manning]

starting to look like a tank now stephen, the real thing but smaller, well done, regards simon.

[Derek Attree]

Hi Stephen
That is a masterful bit of modeling ,I know what you mean about
loctite 480 .
I have found an alternative made by 5 star adhisives that we use in the model boat world
it is a black rubber laoded cyno and it has a 7 year shelf life.

The best thing is it is only £8.50 for a 50 gram bottle.

I have used it on boat fendering to good effect and I am going to try it
on a sample metal to rubber joint to see how it performs..

Derek

[Stephen White]

Derek - looks like a real winner. I've just compared Loctite 243 (£32.95 online for 50ml) with the equivalent from 5 Star Adhesives - £13.99. Bargain if the quality is as good. They've got a very full range of products.

Only downside is the extended summer holiday inJune through to. August.

Thanks a lot for alerting us. Worth a try to save a lot of cash.

All the best.

Stephen

[Derek Attree]

Hi Stephen
The guy used to work for Loctite
They are back next Monday from there holiday.

I have been using these products for quite some time and they seem to
compare quite well so far and dont seem to have the addative that makes loctite go off so quickly.
I have had a bottle of the black rubber cyno from 5 star for nearly 2 years in my work shop on the shelf and it is still runny in the bottle.
It is black and it has stuck rubber fendering to fiber glass and I cant get it off without a blade.

I will try to stick some fender rubber to a bit of ally to see how it works before I try it on tyres.

Regards

Derek

[Stephen White]

Time is coming when I ought to get the motion pack sorted. Finally took the plunge on a LiFePO4 battery to replace the Lead Acid AGM Gel type. Lithium Iron is starting to become available as properly assembled slabs incorporating a built in BCM rather than the self-assembled cell packs which came out first. This is the 20ah slab by Tracer:



This is the performance comparison:



In addition, the LiFePO4 has a very flat discharge curve so I'm effectively getting a much greater relative capacity from 20ah than the 22ah of the lead acid. The main benefits are substantially reduced weight and size. I ordered a simple charger for now - I would have got an Optimate but I believe they are only doing a 12 volt LiFePO4 charger for now.

With the reduced size, the positioning options are much more flexible, so the key factor is probably choosing where the centre of gravity should be. Views on CG would be good to hear.









Last shot shows the built in LED "fuel gauge" as Tracer calls the charge indicator:



Regards

Stephen

[Adrian Harris]

Interested to see how you get on with your cell. It does look a lot more professional that the Eclipse pack I bought.

You will find that the discharge rate is indeed pretty flat, to the point where my T34 just shut down when the BMS decided the charge was too low. No warning, no refusal to turn on grass as per the AGM batteries, it just shut off and wouldn't switch back on.

I did get a much longer running time on grass than with AGM, and indoors at the Tank Museum on the 4th there was really no appreciable drop in battery voltage.

One odd thing was that the tank refused to drive down the ramps from the car when I got home, with the Power Module flashing red as though the battery was flat. The battery pack was still pretty full, and took less than an hour to recharge fully.

I wonder if that was some function of the regenerative braking and BMS fooling the Power Module into believing the battery voltage was too low ?

I've purchased a cell monitor, but I need to open the pack and attach all the sense leads.

Adrian.

[Dennis Jones]

I could buy about five 24volt (2 x 12 volts) gel cells for that amount of money. I do quite a bit of running as you well know and I have not run out of juice yet.

Dennis.

[Stephen White]

Last lap on the running gear - the hub caps. There is a lot of work hidden in these, to get them to an accurate shape but a chance to try out the new Cx5 thermoplastic sculpting clay from Adam Beane.

The real hubs have a very prominent boss and the hexagonal sides are curved:





First the flatter kit caps need to be built up. Cx5 takes a bit of getting used to. It can be transformed from hard plastic to soft clay to liquid using heat, either from an electric frying pan, spirit lamp or microwave. It melts and cools rapidly but by using the spirit lamp flame, the working surfaces are kept pliable for shaping and new material can be added:





Cx5 can also be worked on machine tools. I rough cut the boss on the lathe using the usual turning tools but for fine shaping, I hit a problem, easily solved. A fine file clogs immediately as does wet and dry. Adam Beane uses a hot sanding technique but I found that really fine detail can be achieved just by using a hobby knife blade. It is so very easy indeed to work and new material can be added and removed quickly and easily:



The master boss:



Comparison with the unmodified kit boss:



I then cast the remaining hubs in resin, with a quick coat of Mr Surfacer 500 to finish:





Finally, the bolt details and the sides curved with a mini-grinder and test fitted:



Base coat next.

Regards

Stephen

[Iacopo Di Giampietro]

It seems to me you've got a great result!
Congratulations, Stephen.

[Stephen White]

Good to hear from you, Iacopo. Finished off the new roadwheel hubs:







The hub of the return rollers was a flat disc, whereas the kit shows the retaining nut. Simple job to turn a disc and glue it on:









Replaced the cap heads M4s with csk to avoid fouling the motors:



Regards

Stephen

[Stephen White]

I'm now bench testing the electrics: drive, turret traverse, gun elevation and recoil, smoke and sound. All checked out, very straightforward, although I may have the problem Kevin reported with the elevation motor not turning, despite all the indications being normal.



Listening to the MG sounds reminded me of the discussion about the .50 cal ranging machine gun here:

http://www.armortek.co.uk/Forum3b/viewt ... 4&start=30





I've ordered one of Adrian's MG separator boxes. Of the three MG sounds provided, the first is a passable representation for the .30 coax, the second might pass for a .50 but not in the RMG mode and the last one is, I suspect, intended to be the German MG42 and is totally inappropriate for the Cent. As I mentioned on Adrian's thread, the .50 in its machine gun role fired at a cyclic rate of 450-550 rpm. In its ranging mode, three rounds were fired per burst at a rate equivalent to about 240 rpm. Adrian and Thomas Benedini have found a sound file which is a very good representation of the three round burst and I'd like to replace the MG42 sound with it.

Reading Bruce Cameron's definitive history of Australian armour in Vietnam, Cannister, On, Fire, the RMG seems to have been used in extremis in an anti personnel role on continuous fire. I asked Mike Cecil about this and his reply makes interesting reading:

The L6A1 Ranging Machine Gun (RMG) was later called the ‘RG’ to try and educate users to the fact that it was not to be regarded as a secondary armament, but to be used only when ranging as part of the process of a main armament engagement. There were some very valid reasons for restricting its use to just sighting.

The RG was initiated by the gunner using a foot-firing switch connected to a No.1 Mk.1 Firing Unit – a quite large electro-mechanical contraption inside a cast Aluminium case mounted under the gun mount. It engaged the Maxifort solenoid mounted on the RG three times at each press of the foot pedal, delivering a three round burst (actually, three single shots – the delay between each shot being regulated by the wheels inside the box, which ‘pulsed’ the Maxifort three individual times. It is a real contraption!) The equivalent rate of continuous fire was 240rpm.

The standard .50 M2HB fired at an uncontrolled continuous fire rate of 450 to 550 rpm (actual rate depending upon the set-up, bolt and slide wear, etc).

The Australian Army did not officially bypass the system for the same reasons that the Brits didn’t. However, it was possible for the weapon to be fired manually by the operator, and that’s what happened a lot of the time in SVN: the gunner would track the target while the operator leaned forward and engaged the safety and trigger on the L6A1’s rear plate, until told to cease or the belt ran out. Bingo! an uncontrolled rate of fire of 450 to 550 rpm. Fine if the engagement does not require the operator to do his real job of loading the 20pdr and serving the co-ax MG and RG. But if the operator is busy, then the gunner is restricted to multiple presses of the foot pedal and a slower rate of fire.


I'd like to ask my contacts in Australia who served on Cents in Vietnam whether this was common. I will look at having two .50 and one .30 MG sounds on my Cent.

Best regards

Stephen

[Stephen White]

Use of the .50 Ranging Machine Gun cont'd.

With the benefit of his service as a troop leader in Vietnam and extensive research, Bruce Cameron commented as follows:

You will appreciate that the biggest factor in fighting through enemy positions in Vietnam was ammunition availability. The RMG would never be used for engaging enemy personnel if the coax .30 cal was available. If, however, there was a need to break up an enemy bunker there were a number of first up alternatives: 20pdr APCBC, Canister or HE. If these were running short, however, the RMG could work a treat.

In his book, Bruce adds:

Surprisingly, RMGs were never modified to enable continuous fire. The hitting power of the .50cal meant that it was a very effective weapon in penetrating jungle and engaging bunkers. The operator could override the solenoid and press the trigger if required. Although the RMG was the UK L6A1, it could still fire ammunition used by the more common US M2HB machine gun

Bruce cites an example during Operation HERMIT PARK in June 1971, during a deliberate assault on an enemy bunker complex:

5C meanwhile suffered a loss of power to the turret (possibly caused by the RPG strike). The crew found themselves having to traverse by hand, manually firing the RMG. (Cannister, On, Fire Vol 2 p312).

Thanks Bruce for bringing this to life. I'll be looking at getting the continuous and three round burst sounds onto the model.

I hope this is of interest - the historical research adds so much to the building for me, particularly the contact with those who operated Cents in anger. Thanks all.

Stephen

[Kevin Hunter]

Hi Stephen,

Your build log continues to make amazing viewing and reading, not just because of your incredible detail work but also the snippets of reference info which you incorporate.

Perhaps you should consider publishing your posts in book form when finished - the definitive guide to building an Armortek Centurion!

Did you resolve the issue with the elevation motor? I think (pretty sure ) my problems arose because wires got chewed in the traverse cog - it all worked at the bench test stage and initially once installed. Following my "engine fire" I have other issues to resolve so I've put the tank away until after my imminent holiday. re-wiring it will be an autumn project, and I would hope to sort the elevation at the same time.

Keep up the great work

Kevin

[Stephen White]

Hi, Kevin, thanks for your kind comments, I hope relating my model to the real thing is interesting. Contact with the crews and Centurion experts has made this build the most rewarding I've done and the journey is nowhere near over. I'm still working on the elevation issue.

With bench testing done, I've installed and tested the motors and adjusted the sprockets to align with the running gear:








After a lot of trial fits, I've now resolved the layout. The battery will be forward and the control boxes laid out like this:





The Speed Control Box will be mounted on a new bulkhead which will create a sound box in engine compartment, with one speaker facing rear. The other will be under the turret to bring out the gunnery sounds. This layout will also be simpler to install with hard mounts on the hull sides, making the terminals accessible and allowing the box covers to be removed easily.

Regards

Stephen

[Stephen White]

Like most complex military equipment, tanks are provided with technical publications. I well remember as a young troop leader the monthly tyranny of checking the tech logs, known in British and Australian service as the "417" after its Army reference. The AB417 is a mine of information about modifications, allocation to units, inspection reports and so on. Fortunately, the 417 for ARN 169064 is held by the Australian War Memorial and I've been able to obtain a copy:



With a hundred pages, there's a lot to go through but I've picked out two examples. Firstly here is the tank being issued from the Forward Delivery Troop to B Squadron, 1st Armoured Regiment in theatre in Vietnam at the start of what would be almost 21 months of continuous operational service. Very few of the Australian Cents which served in Vietnam saw through such an extended period in action.



Second example is a record of major repairs done on 19 May 1970 at 106 Field Workshops. "Replace LH Front S/Station, Road Wheels, Repair and Replace L/H Track Guards and L/H Bins". The tank had clearly suffered major damage to the front left requiring the replacement of a whole suspension station. In fact, on the previous day, as recorded in Bruce Cameron's book, 169 had suffered a serious mine strike estimated as a 20 lb charge. Mines were a perennial hazard to tanks operating in close country.



The log book has more to reveal, I'm sure.

Regards

Stephen