A Chequered Chieftain at #10

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Stephen White
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Re: A Chequered Chieftain at #10

Post by Stephen White » Sat Feb 22, 2020 5:04 pm

Richard, the L11 120mm main armament recoiled 35.5cms, as long as there was 500psi in the Recuperator High Pressure Cylinder and it was topped up with OM13. As for speed, the technical description is; f...ng fast to the rear on firing and quite quick on runout. The recoil motion itself was not linear, as the gun moved rearwards, the hydraulic buffers absorbed the recoil force, imparting the deceleration needed to bring the gun to a halt and then the pneumatic/hydraulic recuperator cylinders forced oil to the rear of the buffers to return the gun to the runout position. The technical description for this is: "f....ng quick going back and not so quick the other way". The recoil is the result of explosive force, so a servo is never going to capture that adequately but you can control the runout to a realistic speed. This was my servo based system on my Centurion during setup:

https://youtu.be/6Y6PxeX-Pxk

The finished product is here:

https://youtu.be/dq7lNv8YYZ0

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Re: A Chequered Chieftain at #10

Post by Vince Cutajar » Sat Feb 22, 2020 5:48 pm

Richard

Is your servo the LX3125MG?

http://www.lxrcmodel.com/details.asp?prodid=3896

Vince

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Re: A Chequered Chieftain at #10

Post by Richard Goodwin » Sat Feb 22, 2020 6:25 pm

Stephen,

Many thanks for the 'technical' description. I've watched a few videos now and yes, it is very quick! I'll change my output parameters tomorrow and see what I get. It may be possible to give an optical illusion in that whilst the scale travel was 6cm, the fact that it was very quick means it might not have to travel that distance at all to give the appearance of being quick. Whilst forced air would be the solution, I don't have the tooling or expertise to do that so I'll persevere with this for a while :wink: Incidentally, would you know how long the gun flash lasted?

Vince,

I searched but couldn't find it so thank you very much for that. I'll check it out and do some comparisons against other 25g servos or do I need bigger still? :shock: :shock:

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Re: A Chequered Chieftain at #10

Post by Stephen White » Sat Feb 22, 2020 9:09 pm

Richard,

"How long doest the flash last...."? Difficult to answer really. With the L11 there was very little flash firing HESH and with APDS, such as there was disappeared in an instant with the much more noticeable smoke associated with combustion, followed by a second plume as the bore and fume extractor were evacuated.

See here from about 03.00 onwards.

https://youtu.be/vEd-Q4ZbW4c

Later, with APFSDS, the charge was more powerful and the flash increased but was still not really very noticeable in daylight. At night it was a very different matter and as your gunner reported "firing now" (or "firing the noo" in my Regiment). it was your cue to shut your eyes in order not to lose night vision. Contemporary tanks such as M1 and CR2 seem to produce a much more obvious flash, although these are seen as a plume leaving the barrel rather than a flash in the muzzle. To represent this with an LED in the barrel is really not at all effective, some might even think it's rather toy like. The best method of simulating the effects of firing is really a barrel smoke system. I don't know if Armortek are anywhere near producing one but that's why I spent a lot of effort to perfect my system.

So the answer to your question is "momentary and not from the muzzle of the gun". I know that's not helpful but might give you some food for thought.

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Re: A Chequered Chieftain at #10

Post by Richard Goodwin » Sat Feb 22, 2020 9:27 pm

Many thanks for the link Stephen; that's one of the vids I watched and led to the question since I couldn't see any flash. Would seem a white LED seem more appropriate and perhaps have a 'twinkling effect? Definitely need smoke and lots of it since mine will be a later version therefore firing the latest rounds but that's later hopefully 8)

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Re: A Chequered Chieftain at #10

Post by Richard Goodwin » Tue Mar 03, 2020 6:36 pm

Update time........having had a heavy cold over the past few days, the brain is feeling a little foggy and the patience is wilting so decided that I'd leave the electronics for a little and the idlers and move onto the sprockets.

A few posts ago, I had filed and loosely fitted the sprocket rings to the hubs to check a possible issue with the tracks so I won't be going over that part again.....so here is the new stuff! This is what we are given and where ultimately, I would like to finish up.....
Opening frame.jpg
Now looking at the original, there is a lot more detail on it than the supplied part; that said, all the holes are there! One just has to adapt! Now I wasn't able to find a picture in the manual relating to fixing the hub cover plate; that's probably just me but it is more than likely secured and finished off using two sizes of M3 hex head bolts.

I started with the cover plate first which was filed down to remove any tooling marks then prepped for etch priming. I then made a grease nipple using an M1.2x5 screw and nut; the nut was secured with Loctite 243. i must admit, trying to put that nut on that screw pushed my patience to the limit :x and then I had to do it again! :evil: Once I'd taken a breather, a 1.3mm hole was then drilled on the angled side of the hub cover and the make shift nipple then super glued into position.
DSCF0814-1.jpg
Now looking at the original picture, you can see that the hub cover is secured using castle nuts with cotter pins for security and dispersed between these are an additional 4 normal bolts at 90 degree spacing to each other. I did try to search for some M3 Castle nuts but decided it would be much more fun to make them ( yeah right)!
Make Castlenut.jpg
I made a jig up using an M3 bolt and two M3 nuts acting as a locknut and adjusted such that a nyloc M3 would be positioned at the correct height for cutting. The jig was secured in a vice using the lower nut and the slots cut by eye using a Dremel cut off blade. One down, 23 to go..... As for the cotter pin holes, scratch that, I'll save that one for the more experienced to demonstrate :D
WIth the castle nuts made, it was now the turn of the studs. I used M3 x 16 csk's and loctited them in with 243. Once dry, the heads were cut off at the very top of the thread.
create studs.jpg
A test fit of the hub cover was then conducted and identified that it was quite difficult to remove the cover from the studs even when pushing from behind which once fitted, you wouldn't be able to do. I therefore enlarged the 12 holes relating to the studs to 3.9mm. This allowed the plate to be easily removed using a lump of Blue tack.
DSCF0818-1.jpg
Turning to the last 4 holes in the cover plate, I was considering using M3 bolts with a 7BA head but this didn't quite look right. I then tried an 8BA bolt and nut combination which seemed a lot better.....see below with 7BA head on the left and 8BA nut on the right.
7BA 8BA Comparison.jpg
Also, looking at the original picture again, you can see that these bolt heads appear to have a depression in them which can itself be created with the 8BA nut combination by lowering the thread in the nut; overall, I think the 8BA is the winner!

With the hub cover plate finished, it was time to concentrate on the sprocket ring securing bolts. looking at the original, these look like specific to type bolts; on top of that, Armortek say these need to be high tensile too. I don't think I will be able to buy a bolt like that although I may know someone who could possibly make some but I wouldn't like to estimate the cost so I'm going to use a square half nut and grind a bevel on one edge; its the closest I can get to the original given the cost implications. I'll still use the supplied bolt which is high tensile.
Each nut was held with a pair of electrical pliers to allow one edge to be bevelled..
DSCF0827-1.jpg
The ring itself was given a coat of Loctite 638 on the back of the securing tabs and placed into position quickly then secured into position using the original supplied bolt and nut in alternate hole positions. Then immediately after, the remaining holes were secured using the original bolts and the squared half nuts using Loctite 243 as seen below....
Locktite and secure.jpg
The original nuts were then removed and replaced with square half nuts and again, secured using Loctite 243.
The following day, the threads above the square nut were cut off flush to the nut and the face of the nut ground flat with gentle pressure to ensure the Loctite didn't cook.
Sprocket Ring Bolts.jpg
All done, with the exception of one small detail!!!
Finished sprocket.jpg
Did anyone notice the hole drilled into one of the sprocket teeth? Is it a timing mark or an alignment mark perhaps? Anyone know?

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Re: A Chequered Chieftain at #10

Post by Richard Goodwin » Thu Mar 19, 2020 10:58 pm

Its been awhile since my last post. I've been working on the idlers, the drive cases and the rear end mod but I'll post that stuff over the next week.

I've also purchased two Yuasa 12V 22Ah batteries to connect in a series configuration to power this beast. These batteries were chosen for two reasons; the first being that they cost £76 inc delivery, the second reason being that I don't know if a LiFePo4 BMS could cope with this recharge current! True that these types of batteries wont last anywhere near as long as the LiFePO4 type but it should be possible to at least double the life if a 'smart' charger is used. Now it would seem that CTEK is well liked on this forum so I went looking for a 24V version which I found to be around £140. However, when I checked the reviews on Amazon, there appears to be a significant issue with the 'Mode' button either not working immediately or failing soon after. SO after a quick search on the web for suitable alternatives, I came up with this beauty for around the same price of a CTEK but is much more flexible and variable.

https://www.portablepowertech.com/produ ... y-charger/

3 different charge voltages at 3 different currents per voltage; 8 stage charging including float charge and maintain and much more. Charges Gel, AGM and LiFe battery types as well as and has all the normal protection circuits.

The manual for it can be found here:

https://www.portablepowertech.com/libra ... h--ppt.pdf

If your in the market for a charger, I would give this some serious consideration! Mine is being delivered tomorrow :D

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Re: A Chequered Chieftain at #10

Post by Mark Heaps » Thu Mar 19, 2020 11:34 pm

Richard Goodwin wrote:
Tue Mar 03, 2020 6:36 pm

Did anyone notice the hole drilled into one of the sprocket teeth? Is it a timing mark or an alignment mark perhaps? Anyone know?
That dimple is the wear indicator and was used as follows.
The leading edge of the sprocket teeth would get the most wear with most movement of the tank being forward. When the leading edge of that tooth wore down enough to reach the wear indicator. the crews would split the tracks, remove the sprocket rings and reverse them. When the other edge also wore down enough to reach the wear indicator, it was time for new sprocket rings.

Generally the tracks would also need to be replaced at the same time time as new sprocket rings were fitted but condemnation of the tracks required REME authorisation. Normally a quick visual inspection would be enough to say "They´re f**ked !" but we also had Go/Nogo guages that could be used to prove still servicable or unservicable but they rarely had to be used.

Mark

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Re: A Chequered Chieftain at #10

Post by John Clarke » Fri Mar 20, 2020 3:38 pm

That's a neat looking charger Richard, adaptable for different batteries, charging modes and voltages. Just what you'll need to look after those expensive batteries you'll going need.

Mark, you'll be pleased to know the term for worn out technology is still alive and kicking :lol:
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Re: A Chequered Chieftain at #10

Post by Richard Goodwin » Fri Mar 20, 2020 8:41 pm

Many thanks for the explanation Mark; was it just the one hole per side? I'll be adding a suitable size hole now to each of my sprockets :D

John, having received the charger and now used it, I can confirm its a nice piece of kit and relatively easy to use.

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Re: A Chequered Chieftain at #10

Post by Mark Heaps » Fri Mar 20, 2020 10:20 pm

One tooth on each sprocket ring had the wear indicator and it was on both sides of the tooth.
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Re: A Chequered Chieftain at #10

Post by Mark Heaps » Fri Mar 20, 2020 10:57 pm

Just to clarify. The wear indicator is not a hole that goes through the tooth but a concave depression on each side. If memory serves me correctly, it was only about 5-6 mm deep at the middle point so as not to adversely affect the structural strength of that tooth.
I would suggest the best way to replicate it would be to drill down 1.5 to 2mm, fill the hole with paint, and let evaporation of the solvent create the concave effect.
Mark

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Re: A Chequered Chieftain at #10

Post by Richard Goodwin » Sat Mar 21, 2020 11:28 pm

Just thought I'd post a few pictures of the new charger........
DSCF0878-1.jpg
DSCF0879-1.jpg
DSCF0880-1.jpg
DSCF0881-1.jpg

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Re: A Chequered Chieftain at #10

Post by John Clarke » Sun Mar 22, 2020 8:53 am

Looks impressive

You can charge your phone or iPad at the same time too :!:
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Re: A Chequered Chieftain at #10

Post by Richard Goodwin » Sun Mar 22, 2020 4:12 pm

John Clarke wrote:
Sun Mar 22, 2020 8:53 am
Looks impressive

You can charge your phone or iPad at the same time too :!:
As I understand it John, yes you can but you'd need a battery connected first!

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