Amateur Build. HAYA Centurion KIT

[zooma]

This is turning out to be more of a kit than I thought it would be. And that's a good thing! An interesting build you're documenting that will be quite useful.

Mike.

There are “one or two” more things to do than you would expect to find if this were a Tamiya r/c tank kit, and (as previously mentioned) there is very little in the way of guidance inside the kit box (none at all !).

With no building instructions to refer to, I guess there is not so much point in having numbered parts diagrams either but these would come in handy when trying to identify any part that may need replacing in the future.

An “exploded” parts drawing would have been really helpful as it could effectively replace a build manual by showing where the various parts fitted and could become a reasonably effective building guide - but we don’t have one of these either.

The lack of any information regarding what type and size of screw to use has not been the problem that I had feared it might be.

Careful checking of the parts that need to be screwed together makes the choice of screw reasonably obvious with self tapping screws being used in plastic to plastic joints and machine screws being used for joining metal parts together.

I have not even looked at the upper hull or turret assembly yet, but so far everything has gone together ....well enough...

[zooma]

The steel pivot axle for the cast return wheel housing and cast axle assembly is held in place with a 2.6 x 6 machine screw on each end to retain it in the cast housing (inside) and to retain the cast front return wheel on its outside end.

The coil spring has a leg that engages in a slot on the axle casting and a "leg" on the opposite side that engages in a hole in the main casting housing. There are 6 holes to plug the spring "leg" into to allow different levels of tension to be applied to the coil spring. The whole assembly feels a bit "loose" when it is completed . I need to take a look at the RTR Centurion to see if I have made a mistake in the way that have put it together, but I think it can only fit the one way.

When the assembly is completed, one bearing is slid onto the cast axle to act as the inner wheel bearing and this slid on. These cast axles are a good fit with the bearings that just slid-on to them. The other wheel bearing sits into a hole in the outer side of the cast return wheel.......or at least it should do!

The outer wheel bearing will not fit into the deep hole in the outside of the cast return wheel. Firstly the hole has a smaller diameter than the bearing width (!) and secondly, there is a blob of unwanted cast alloy right on the base of the hole (it should be flat to allow the bearing to sit squarely on it) - so even after opening the hole out to be wide enough for the ball bearing to fit into it, the bearing cannot sit flat at the bottom of this hole as the small lump of alloy casting "flash" will be holding it up away from the base.

I will take another look at this in the morning, but I don't really want to have to mill or drill out this hole to make it wide enough, or use an end-cutter (in a milling machine) to machine a flat base for the bearing to sit onto. There must be a simpler way of doing this that I will find.

To date, this has been the only part of the KIT build so far that has caused me any real concern - but any problems will no doubt be resolved after they have been given "a good coat of looking at".

The way I see it I have two options . One is to ask HAYA to replace the front return wheel castings (both are too tight for the bearings to fit into), and the second is to find a way of correcting it myself - preferably in a simple way without the use of machine tools.

Thinking about these wheel castings some more - I had to file away a small lump of hardened metal to get the wheel halves to fit together correctly. The type of alloy used to cast these parts is quite hard and so it was not easy and took some time to file away using the end of a small diamond file to get in-between the raised studs (no access for a flat file).

The small hard lump of metal that need's to be removed from the base of the hole also looks like a little blob of molten metal has dripped onto the casting and set hard......not sure how that could happen, but they need to be removed.

[zooma]

I have taken a fresh look at the problem with the return wheel casting this morning and decided that I want to try to resolve it with basic hand tools because that would be the way that most buyers of this kit would have to do it, and if it fails, then replacement castings would be the other option available to anyone building the kit.

My small square edged diamond file was used to scrape away in the bottom corner of the casting to slowly grind away the lump of alloy that had formed in the base of the axle recess - this being the priority because until it was removed the wheel bearing could not fit down into its correct position against the flat base of the hole.

After half an hour or so of careful scraping the lump has been removed.

My next job is to work out how to open-up the bore to allow the ball bearing to fit into it without either making it too loose a fit and without touching the base so that the depth of the bearing fitting remains unchanged. Being a casting there is always the possibility that the bore hole that has been cast into it is not parallel - with some luck it may be tighter at the top entrance (the easiest problem to resolve!).

The light grey primer colour has also made other parts of the casting that need cleaning-up a lot more visible, so I will be attending to them at the same time.

[zooma]

A 9mm HSS drill bit was hand held and rotated inside the bore of these Return Wheel Castings and gently "worked" back and forth until it could be rotated freely.

The markings inside the bore showed that it was (as suspected) tapered (narrow at the top) and not parallel as it should be. Once this was done the bearings fitted into the bores freely and were able to sit squarely in position at the bottom of the bore as they should.

Problem solved - using simple hand held tools........and on a lesser note - it also explains why the hub caps on these wheels were so hard to remove - they must have been pushed in under a lot of pressure to force them into the mouth of these narrow tapered holes!

[Herr Dr. Professor]

zooma, if your's is an "Amateur Build" my skill level is Bozo Build. Gee I wish you were nearby to help me when I tackle a Puma or even the Asisatam Kubelwagen--but the puddle is too big to jump. I'm watching all along with R-E-S-P-E-C-T.

[zooma]

The alloy front return wheels have now been fitted using m2.5 x 7mm stainless steel cap-head screws with a single 2.5mm stainless steel washer under the head. I ran out of the specified kits 2.5 x 5 machine screws, but these cap head fitted and work well and I actually prefer working with a hex-head screw rather than the cross-head types.

I removed and re-fitted the cast front support assembles from each side of the hull and following some small adjustments they no longer have any 'free-play" but fit nicely together and move freely so now I can move-on to fitting the motors and gearboxes along with the rear sprockets to complete the lower hull mechanics.

[zooma]

I have test fitted the RED motors, and fully screwed them into position ( x3 2.6 x 6 STS screws in each motor mount into the chassis) in the hope that once they are secured a slightly bigger gap would open-up between the lower motor and the gearbox next to it in particular.

This did not happen (!). I was advised that I would have a 1mm gap between the lower motor and the gearbox side closest to it - but I think it is closer than that!

I made sure that the solder joints were as flat as they could be to the rear of the motor and the tabs that they were soldered to were as flat to the end-cap as they could be - but it looks very close.......but maybe not actually touching!

A piece of thin plastic card will be pushed in-between the lower motor and the gearbox side that it (almost) touches and I am hoping that this will provide some insulation in the event that any movement when the tank is moving will be absorbed to stop the motor actually touching the metal gearbox side and shorting out.

Sadly it all has to come out again in any case. When I turned the sprockets the gearbox with the lower motor mounted to it was very tight to turn over, whereas the gearbox with the higher motor mounted to it turned nice and freely so I need to make a look at the tight gearbox to find out what is wrong and correct it.

[zooma]

The shorter BLUE motors would give a safer fit - but would they improve the performance over the standard motors?

[ongbenghui]

This did not happen. I was advised that I would have a 1mm gap between the lower motor and the gearbox side closest to it - but I think it is closer than that!

Yeah, I will suggest don't risk it. it is too tight of a fit.

This is what i had in mine.

IMG20240912115956.jpg (127.13 KiB) Viewed 718 times

[zooma]

Your installation looks "safe" and to be fair I am not looking for a racing Centurion - just one that has enough power to run across my lawn without stalling.

I think when I remove the gearboxes I will try fitting the BLUE motors. My RS-380SH motors don't have the same backplate as the ones you have pictured - but the BLUE motors do, so maybe they are the same (or similar) with a coat of paint? I will fit them anyway and hope they have more power than the standard motors that come fitted to the gearbox.

As a matter of interest, I think I have devised a way of fitting the RED motors into my HAYA Centurion.

There is some spare space on either side of the gearboxes and the inside of the HAYA chassis tub moulding. Only three moulded mounting points are available inside the HAYA Centurion chassis tub, so by re-drilling the three matching holes in the steel gearbox frames 2mm inwards (to push the gearboxes 2mm outwards) I will gain 4mm extra space between the gearbox - more than enough space to clear the RED motors.

The output axles will need exactly the same 2mm removed from their length to keep the drive sprockets in line with the rest of the drive train and the axle "flats will also need to be extended inwards by the same 2mm.

The ONLY problem that I can see with this modification is that the Kermit Green housing for the output bearing would come too close and removing 2mm from the face of it would be easy - but machining out the base of the bearing socket by 2mm to move the bearing outwards by 2mm would not be quite so easy - but maybe a suitably sized bearing could be fitted in the outside socket in this mounding instead ?

Another possibility would be to move the gearboxes outwards by only 1mm. This would gain 2mm clearance between the ends of the RED motors and the metal sides of the gearbox cases and may not need the output bearing in the Kermit Green housing moving at all? The extra 2mm space should be plenty to give a safe working clearance between the end of the RED motors and the gearbox sides.

I think I will test my idea on a pair of cheap plastic geared gearboxes that I can re-work without worrying too much about the cost. I think the idea will work well in any case, but by making a working "mock-up" that I can "insert to test" and "remove easily" will be an interesting experiment.

If I can buy a spare pair of the matching Kermit Green mock external gearbox cases from HAYA I can also test the theory of moving the gearbox mounting outwards by the full 2mm and relocating the output bearing from the inside to the outside of this moulding. This would give the full 4mm space between the RED motors and the gearbox frame sides (my original idea) and should give a very safe installation with no fear of the motors ever touching the gearbox frames.

This will be a nice future project that is not really too difficult or complicated to achieve and will allow the HAYA Centurion to gain a pair of the more powerful RED motors IF the BLUE motors do not give any power increase over the standard motors.

UPDATE:- I have bought two pairs of the dummy transmission mouldings from HAYA ready to be "modified" when I get around to making my "wide mounted" gearboxes to accommodate the larger RED motors. This experiment will not slow down or interfere with the KIT build as it will be done at a later date - and if the new BLUE motors work well enough - it will not get done at all!