Used Challenger Strip and Rebuild.

[zooma]

Now that I can access all of the TK24 controls I can test drive the tank, and this has shown a fault.

When the turret turns, the entire top deck can be seen to move forwards a little when the main gun is pointing in a certain direction - and this is because the turret turning motor gear ring is touching something.

Fortunately the very poor upper-lower hull retention magnets don't work very well and the power of the turret turning motor is strong enough to push the hull top forwards (quite easily!).

Initially I thought the third angle alloy cross brace that I fitted infront of the engine bay may have had something to do with it - but this is not the case as the turret turning motor is screwed onto the underside of the top deck and does not actually move when the turret is turning.

I need to check further as the ring gear is close to the sides of the alloy frame and may be touching something that is allowing it to "walk" forwards.

Some Velcro that I added to the inside of the alloy frame to retain the LiPo is in about the same area as the ring gear, so it has been moved to sit underneath the frame sides.

One of the securing screws on the side of the alloy chassis frame is also a bit close to the side of the ring gear so I will also check that to see if it needs to be modified or relocated.

This will also give me the excuse to change all the cap head screws that I used to fix the alloy frame parts onto the hull as the stainless button head screws that I ordered for this job have now arrived!

[zooma]

The 16mm stainless steel cap head screws (that I had temporarily used to hold the alloy chassis frame to the moulded plastic hull) have been removed and replaced by new shorter stainless steel 12mm long button head screws.

These new shorter screws give a much neater fixing and also gives more clearance to the underside of the hull where the tracks turn very close to these screw heads underneath.

Changing the screw head shape from cap heads (cheese heads) to the new lower profile button heads (round heads) will also allow any part of the track that may come into contact with them to slide over them rather than crash into the vertical side walls of the cap head screws.

This change of screw head shape will give smother running when the tracks flex over rough terrain or when running with a less than "taught" track tension.

The turret no longer "walks" the top deck forward over the lower hull (when it is turning) as the shorter central chassis frame mounting screw does not come into contact with the underside of the ring gear. Marks on the underside of the ring gear show that it had been touching this central mounting screw before it was shortened.

[zooma]

The Challenger 2 was designed to have the upper and lower halves of the hull held together with 8 self tapping screws.

These 8 self tapping screws also help to prevent hull flex as when the two halves of the hull are firmly screwed together they form a fairly rigid monocoque chassis assembly.

When the drive battery is relocated inside of the hull and access is needed to change the battery and to gain access, these screws are often removed and replaced with magnets of some sort or other.

This particular used Challenger 2 is in a bit of a mess as far as these fixings points are concerned.

Most of the 8 moulded pillars that would have had the ST screws inserted into them from the underside have been split, fractured or broken off - no idea why - because most owners who converted to magnet fasteners would have made good use of these pillars as a magnet support or a mounting reference anchor point.

Even one of the 5 moulded pillars that the ring gear is screwed onto has been snapped-of (!) and one has has the screw thread stripped - leaving only 3 of the 5 fastening points to hold the ring gear in place!

I need to make a fair bit of repair or reconstruction around these pillar areas to create a platform for mounting either a) fixing studs to locate into the remaining lower pillars that are still present in the lower hull, or b) possibly to hold matching round magnets to grip onto the small round magnets that have been inserted into the lower pillars....or c) a combination of both depending on the damage inflicted in any particular area and the best way to repair/reconstruct it.

..........and d) reconstruct and repair two of the five moulded pillars to hold the ring gear on securely.

The alloy frame will prevent any chassis flex, so only a suitable retaining system needs to be devised to keep the two hull halves TOGETHER and ALIGNED.

The use of some larger sized rectangular shaped magnets mounted on (or close to) the alloy frame parts will also be considered to give a better "grip" between the upper and lower hull parts with some form of mechanical alignment to prevent any "wander" that most magnet retaining systems suffer from as they fail to prevent any lateral movement - even if they keep a strong enough grip on the two main hull halves to stop them coming apart - they often fail to keep them in the correct position.

[Herr Dr. Professor]

zooma, I am impressed by your rebuild of this Challenger 2. I am currently converting mine from HengLong 5.3 to 7.0, making all my own new connectors. That's a challenge for my relatively inexperienced skills. What is more, nowadays because of a house demanding repairs and car replacement costs, I have to be frugal about my hobbies (Drat! #$%^&**&%$#0 ! !). I don't wanna be frugal about my hobbies!

You would find this experience risible: after getting all the new connectors set up in the HengLong 7.0, I could not get anything to work. So for a second time, I spent five hours re-testing every connection from the functioning part out to the connector for the board, step-by-step, for continuity and with voltage. All was fine. Eight hours later, a little light went on in my shriveled brain : The switch which fits in CN-1 on the TK7.0 must be used: the (now redundant) on-off switch from the 5.3 can be on, but without the CN-1 switch, the 7.0 board will still not be on.

[Meter rat]

You would find this experience risible: after getting all the new connectors set up in the HengLong 7.0, I could not get anything to work. So for a second time, I spent five hours re-testing every connection from the functioning part out to the connector for the board, step-by-step, for continuity and with voltage. All was fine. Eight hours later, a little light went on in my shriveled brain : The switch which fits in CN-1 on the TK7.0 must be used: the (now redundant) on-off switch from the 5.3 can be on, but without the CN-1 switch, the 7.0 board will still not be on.

Sorry. I nearly choked on my whisky when I read this. We have all done something similar.

[zooma]

Herr Dr, Prof. As a matter of interest the Challenger 2 that I will be working on when this used Challenger rebuild is completed came with the 7.0 radio'.

If any pictures of the circuit board or connections etc would help, please let me know.

[Curgenven]

The Challenger 2 was designed to have the upper and lower halves of the hull held together with 8 self tapping screws.

That's interesting, as the new one is only held together with 6 screws. I wonder if that means the the older one is inherently sturdier when held in its intended way than the newer ones?

[zooma]

There are a few small details changes between the older and newer Challenger 2 model, - this old used one that I am rebuilding has no track adjusters - something that I will need to look at in the future.

The only way that I can adjust the track tension at the moment is to add or remove links !

[zooma]

I took this used Challenger 2 to our local club for its first proper run last night, and overall it performed very well.

The TK24 worked OK and I was able to find all of the functions (on demand) so that was very satisfying as it is running with all the drive controls on the right hand stick and everything else (Sound on/off, Drive on/off, MG with flash, Lights on/off, Main Gun with flash, MG2) on the left hand stick.

A strange sound when driving (a bit like a cross between a squeal and a rubbing sound) was inspected and it was found that the tracks were rubbing against the underside of the moulded chassis - at the front above the return wheels.

The metal tracks are rubbing at a point just on top of the front return wheels. I am not sure what to do about this as the I don't have adjustable track tensioners on this early model so they are fixed in the position that they would have left the factory with.

In all fairness, I remember the seller saying something was rubbing somewhere - this must have been the area he was referring to as I can see no other places that are rubbing anywhere. The rubbing away of the plastic and paint in this area suggests that this has been the case for some time.

I had wondered if adding the metal frame could have contributed to this problem - but if anything - the fame is helping to lift this part of the hull away from the track at this point!

I notice that the front return wheels have a "negative camber" and so they are mainly rubbing on the outside edges of the tracks.

My first thought is to cut away the flange in the area that the tracks are rubbing it. I can't see this doing any harm and at the moment I can't think of an alternative - other than letting it continue to rub as it must have been doing this since it was new?..........or maybe since the metal wheels and tracks upgrades were fitted?

The RED motors powered the tank along nicely, but it must have been a bit like driving with the brakes on! I rather suspect that the tank will run smoother and faster once the drag brake has been removed.

Checking my other Challenger 2 (that is waiting for some attention when this used model is finally "sorted"), I noticed that the metal tracks on that one also run VERY close to the underside of the moulded chassis at the same point above the front return wheels. This is a much newer model that does have adjustable track tensioners, so maybe that is the difference between the tracks rubbing or not rubbing at this position when metal tracks are fitted?

[zooma]

Nothing to adjust !