Scratchbuilding C&Cs Mammoth Tank

[Munty]

Time for ANOTHER update! Only a little one but I've gone ahead and made the little bit of test track I wanted adn it only took me 20 minutes! It seems I've got myself a nice little production line sort of thing going on over here so maybe it won't be as bad as all that after all... Anyway here is what I've done briefly, starting with all the pieces for the build.

On the left are the 2 double drive wheels I'll be using and a pile of pins that's barely visible due to the sunlight! In the middle are all the untouched track pieces that need to be destroyed for the next test and on the right is the 18link track I've already finished. For the next step I'll be making 14 more links so I have 28 pieces ready to butcher.


In a matter of about 8 minutes I managed to get all 28 links cut to size and this is it ready to be put together!


And here is the final construction. It actually took longer to assemble than it did to create the pieces. Every other link needed a little fine adjustment before fitting so that took up most time!




Again, this assembly was given to my nipper to play with for a while but obviously it's harde for him to abuse it in this setup without partial failure. The sprockets are still in 3 pieces so occasionally the back piece would fall off or hop out of the track and even with the tiny amount of slack I've given this piece it was still enough for his over-excitement to skip a hole every so often. All in all the toddler-test was a rousing success though and remember there is STILL no glue anywhere to be seen!

I've now prepared all the pieces I'll need to fully assemble one of four tracks so that will be the final phase of testing! I'm trying to decide on suspension, drive and bogey wheel positions and mechanisms before I go any further so I may or may not do more today. Post has arrived and sadly still no grill so hopefully it will arrive tomorrow as that will have been a week. Here, as a parting gift, is my next pile of pieces to mutilate!

[[ICE]monkey]

wow talk aboit giving yourself a job, looks like youve got it sorted though, looks good to me
regards, ice

[blimp]

HOLY MOLY ! That's some package Neat fix for the track width , the 'brick work' system is a very neat touch . - Are you staggering the pins as well ? - Mucho impressed . Blimp.

[Munty]

Hi guys, thanks for the kind words! I must say I'm amazed I haven't had any pointy comments yet as I'm sure what I'm doing must be cray but meh maybe it's not as unlikely to succeed as I at first presumed

I've gone ahead with this method anyway and I now have some pictures of a full track to share! I won't be doing the other 3 for a while though as it's now time to finalise how to arrange the sprockets and bogeys and such, not to mention how to provide drive to a wheel in constant contact with the ground whilst still allowing it to be sprung... Thankfully I have a few thoughts on this which I'll be sharing shortly!

Before I get into pics, thanks ICE, I got into a nice rhythm with this method now but it still takes a lot longer to put them together than it does to cut the pieces to size! And blimp, I'd like to replace the twin pins with single 73mm ones (yep that's the final measurement of how wide these tracks are!) but that will require a staggering 26 meters of 1mm metal bar! I'm not convinced I can get that amount of metal cheaply anywhere so perhaps staggering them will be a cheaper alternative... You'll notice in these images I've actually pushed all the pins through to one side and it hasn't affected strength too much but I'd rather stick with either a central join or no join at all if I'm honest...

Anyway, now for the last pics of the day before I turn in and hope that my grill arrives tomorrow I didn't feel any need for WIP pics as the method of construction has already been explained (and what hasn't is a highly guarded secret aha!) so we'll get straight to the meat. From left to right here is a Tiger track at 43mm, a King Tiger track at 51mm and the newly forged Mammoth track at 73mm!


I tried to mock up a few images of the track how it will be used but these are all pretty crappy I'm afraid. Here is one of the general position it will take though. Sadly it's shorter than I expected so more links will need to be added in the future which will add to the already high number of 296 links! Looking on the bright side I've done 74 just today


Here's a slightly better representative image to show the overall track width compared to the armoured carriage that will house it. There's about 8mm space either side of the track which amounts to 12.8cm in a real world scenario. More than enough I think but not too much as was the problem before.


This was me playing with the sprockets but of course everything just wants to droop without any support at the top. I used a piece of the hull top (the engine cover!) to keep the sprockets apart for this shot. Looks good...


So one out of four tracks is done! Or at least it will be when I get round to adding a few more links but that can wait... Other good news is that the 16 sprockets I have will make me 8 double width drive wheels so that part of the build is now accounted for. I also have 4 gearboxes which will do nicely and 2 sound and 2 smoke units for later down the line if I decide to get fancy! I have other stuff too but I don't get how the controllers work so that can wait until the tank actually looks a bit more like a tank for now...

My next job, until the grill arrives at least, is to finally decide on the bogey, drive and suspension arrangements for each track. All four will be identical which saves work but I could use some advice on this from people who know what will work and what won't. I've been doodling this evening and think I have a good solution which for now I've thrown together as a quick paint image. Here it is, explanations follow...


As I've said before, the Sketchup file I'm using is NOT my work and also is not entirely accurate but it makes a great background for this example... Obviously the green line is where I'd like the track to run and red circles are the sprockets and such. The largest ones in the botom left and right are my double width drive wheels as seen above, smaller ones are bogey wheels which will need to be scratchbuilt or modified from existing kits/models.

Due to the width of track I'm using, all the bogey wheels will be double width and 3 locating tangs (instead of the usual 2) will keep the track running along them centrally. The four wheels on the bottom ( I know there need to be four from original game artwork) would be best as two twin mountings in my opinion so that's what those wierd arrow things are meant to represent! Now I know what these are and how they work etc. but for the life of me I can't determine whether this kind of arrangement has a specific name. Please let me know if it does as it will help my googling and ebaying where necessary! The 4 wheels at the top will be the same double-bogeys (no golfing pun intended) as used in the bottom but they's be permanently fixed in position with a rod which will pass through both sides of the track carriage, allowing them to rotate freely but not to move in any direction.

Now the contraption emanating from the small circle in the centre of the image is (I think) of my own creation. I've certainly not seen it used before but it makes logical sense in my engineers mind so I'm going to put it out there for some feedback... I'm thinking that as I must place the drive wheels on the ground and as they must be driven and sprung, there are very few solutions. This is the one I've come up with though...

Each track has the final drive of it's controlling gearbox entering the carriage centrally. Instead of being attached to a sprocket as usual it will be attached to 2 gears which will drive small chains (think bicycles and such) This chain will run to a similar gear fastened to the rear of each drive wheel at both the front and rear of the track. It will be constantly tensioned as both the final drive gear and the gear on the drive wheel shall be attached to opposite ends of a long inflexible strip of material. The end of this material to which the drive wheel is attached will be free to move in an arc with the final drive as it's origin and this will allow upward movement of the sprocket whilst maintaining permanent drive of the belt. Downward movement will be prevented by the presence of the track, upward movement will be limited by a stopper and a suspension unit and this same unit will ensure the normal position for each wheel is at the same level as the four bogey wheels between the two drive wheels.

As you can see from the illustration there are also two green circles to the left and right which serve only to control the path of the track to something more pleasing and reflective of the size and shape of the carriage itself. I'm currently uncertain how to implement this as there will be little room in either of the areas indicated so bogey wheels are out of the question. I'm thinking that a sprung tensioner could be the answer but rather than have it mounted inside the track pushing out I could install it from the outer edge of the armour and have it pulling the track instead. I'll explain more and possibly share some more detailed illustrations tomorrow but for now I'm ready for a good night sleep!

Any thoughts on the above please be sure to share them. Good or bad, I'd rather any flaws were revealed now than weeks from now when it's too late to avoid catastrophe! As a parting gift here's an image of the way I left the track before I sat down to write this update. Purely coincidental but I give you 'Love and War'!

[blimp]

- - - Yo , Munty - you can use a single gearbox / sprocket like this , the whole caboodle can the pivot at the cross mark ( it'll be hidden by the sponsons , and a standard twin cog sprocket can be used to drive it all , keeping it simple to set up ) this way all the wheels can be free to conform to the terrain , leaving you just the small wheels to spring . I am doubtful that a combined twin sprockets / chain drive will work - every tooth and track link would have to be in perfect sync . unlikely - any missmatch will cause stress/derailment/breakage !

. . . a small sprung loaded 'return roller' under one of the top runs will keep it tensioned . B.

[Munty]

Thanks Blimp, this is just the kind of feedback I need! Shame I don't understand much of it though haha Where and how would you suggest I transfer the drive to the wheels and do you think it should have just one or both of them powered? And do you have any images or something of the sort of suspension I could use on the big wheels and how to implement it?

Also anyone who can provide me with some bogey wheels (64 of them should do!) that would be nice... Need to be 30mm or less

[blimp]

- sorry M , i didn't make it very clear . the yellow + is the gearbox sprocket , the gearbox will be in the hull with the shaft protruding out into the sponson driving the track from the top . All other wheels including the sprockets touching the ground count as normal road wheels . The track needs some slack , to allow the suspension to travel across the lumps and bumps of the road . To stop the track coming off , adding a sprung 'jockey' wheel to press against the underside will keep it at the right tension automatically . this only leaves the suspension of the bogie to sort out . - For ideas , why not check out different types used on other tanks and adapt them to suit .

. . Clear as mud

[Munty]

Thanks blimp am with you now Only trouble would be my lack of drive wheels as I have exactly enough to create the 8 on the road but none to make the extra 4 that I'd need at the top... Am off out for a bit now so will continue thinking about it but I took delivery of parts for my priority project today so I have 3 jobs to do on that now

Keep thinking about it and I'll pop back in later to gather any new ideas lol

[blimp]

Mammoth circuit idea - or Blimps ' saturday brainfart # 1 '

. . . The yellow arrow is the direction of travel .

Gearboxes are the black things , shown here in back to back form , they can be all facing the same way if space permits .

Now the brainstorm bit -

• . . . As a single RX18 will blow , why not have 2 ?

. . . Then the problem arises on how to control them both at the same time , I don't know if it is possible to run both '18s with a single RX board ( dk green dotted line ), i don't know what currents etc. are involved , maybe someone on the forum can help ? - if not , another option might be a second RX board with the SAME CRYSTAL .( Lt green one ) - Like running two tanks simultaniously using one transmitter

Both circuits to be powered by a single 4000 ma ( or bigger ! ) battery , keeping power delivery constant to all components - it'll stop the ' dog dragging it's bum across the carpet ' effect of having one set of drives lose power . On that charming note i'm off, to do some mischief of my own . . . .

[Munty]

Thanks Blimp, stuff like this is REALLY helpful for me as I've not got the slightest clue where to start with the electronics! I'll give you as much info I can to try and finalise this before it's needed as then I should be able to keep building right through As I said I'm still working on my other project right now which will keep me busy for some time as I have about 300 tiny apples to put on some 1/100 scale trees haha

Anyway, I've already posted images of the hardware I have so you have some idea of what I've got already. Just had another look though and I have all 4 gearboxes, 3 of the Heng Long 'multi function boxes' and 3 of the circuit boards as well. Interestingly I'm googling these parts before I ask you what they are and a lot of links lead here to RCTankWarfare so I think I've certainly picked the best site for this build I see the MFUs I have are RX18s so I already have 2 of those which is another piece of the puzzle completed.

I also see that the other circuit board thing I have three of is a reciever board (again thanks to posts on this website!) and so I have 3 of them as well! That means I have all the parts I need for this build already, including 2 smoke and sound units which would be very cool to use in conjunction with a twin-engine setup (if I can find suitable models for them!)

I had thought about using 2 'receivers' but at the time of pondering I had no idea how the circuit behaved so now you've allowed further pondering on the matter Now in theory it seems to me like that should work fine so long as they're both capable of receiving the same signal simultaneously. If that means using the same crystal then I have to ask what and where is it? And does anyone have some I can use :p I need to figure out what else is missing too as I know I'll need a battery and aerials (the tank has 2 radio antenna anyway so I'll use them) and also a motor to turn the turret.

I've just put the vital parts into the hull for a very rough test fit and there's enough space to put a whole extra vehicle in there so that won't be a problem! The recievers and MFUs fit quite nicely between the motors which should leave a sizeable gap in the centre of the hull for a battery/batteries to keep the thing powered up for a week or two between charges

At this point I'm thinking about building a thin sheet metal trough to line the bottom and sides of the main hull compartment. If made from a single sheet it will ensure there are no weak points in the way of corners (which the current construction has plenty of) and also give more secure and long-lasting mounting points for all the hardware. If possible, suspension mountings and the like can also be attached to this metal reinforcement at one end rather than relying on the strength of just plastic. I'll come to a final decision on that when I've finished planning how the tracks will run though.

I've been thinking more about driving the tracks from the top and I wondered if it would be possible to simply make 4 more drive wheels out of other materials to do the job? All they need to be is metal cylinders with a correctly spaced sprocket wheel attached in 3 seperate places. Noone will ever see them and it could solve the problem, I imagine I'll struggle finding yet another 8 sprockets to complete the task that way at any rate! Of course when I've finished making all of the double sprockets from the 16 I started out with there will be 8 spare 'faces' but no spare rears. If I send the faces to a fabricator of some sort with a small amount of belt, all that would be needed is the introduction of a third part between the 2 to make them a perfect fit for use as a drive wheel... The only other thought I've had about driving from the top of the track is that it would probably mean monuting the boxes upside down which I imagine has rarely been resorted to as an option! The highest point of the track is almost level with the highest point of the vehicle so it would be very difficult to install them right-side up in this situation.

A final question, in your image on suspension, do the yellow lines represent a sort of triangular shaped 'mout' on to which both drive wheels would be fixed and then allowed to rotate around the gearbox sprocket as means of suspension? Not sure if I'm even on slightly the right track so please set me straight either way If the above is intended though it does strike me as only a partial solution as technically only the leading wheel would be sprung in most situation with the trailing one being fully dependant on the motion of the former. Excessive travel would also allow the wheels to become very close the the carriage and introduce the possibility of fowling... Let me know your thoughts, and also what do you think about a method of keeping the track in the desire shape from my image? The small green circles at front and back represent where I'd like it to run but I'm not sure how I could achieve that...