3-1-12

Thunder Tiger MT4 G3

 


 

   
 
 

Upgraded Thunder Tiger RC Parts

For my latest rc car I decided to step up in size to 1/8th scale. What you see here is a Thunder Tiger MT4 G3 made by a company mainly known for rc helicopters.  I have actually never seen a print ad for their rc cars and found out about this particular model via several internet forums: the best being the dedicated Wondertiger.Com fan site.  The general consensus was that it was built like a tank and judging from some of the YouTube bashing videos I saw I knew it had some potential.   I ordered the kit from Tower Hobbies along with the optional front sway bar and Castle Creations series adapter.  Turns out I did not need either parts as the kit comes with a front sway bar (you just have to install it) as well as a series adapter to connect two 2S batteries together to make a 4S battery. There are quite a few reviews out there as well as unboxing videos (who watches those things?) so I won't go into all the minutia.

On paper 1/8th scale doesn't sound like much of a step over 1/10th scale until you set it down next to the smaller scale. This truck is actually very similar to the nitro Thunder Tiger ST-1 stadium truck which has been out for a while.

Just look at those tires!  The bead locks are not functional so if you like the blacked out look you can remove the colored rings

One thing that is going to take a while to get over is the incremental increase in size of all the MT4's parts. It is like I need to get my eyes re-calibrated. From axles to rod ends to the included tire nut wrench; they all exhibit an aura of heft that is absent from their 1/10th scale brethren.  The above picture on the left compares my Losi Desert Truck axles to the MT4's axles but perhaps the most eye popping example is the comparison shot of the MT4 vs. Traxxas Stampede wheel nut wrenches.

The truck is powered by a 2000kv motor and requires a 4S lipo minimum despite what the Thunder Tiger website says.  While the ESC will power up with a 3S I could not get it to actually move the car well despite a high quality 50c 3S battery. The motor transfers power from it's 12 tooth pinion to a center mounted oil filled differential before sending power to the front and rear differentials. Based on recommendations from other owners I replaced the light weight oil in the center differential with some 100k weight silicone oil, 50k weight oil for the rear differential and 40k weight for the front. I had read online that Thunder Tiger was one of the few ISO 9000 model manufacturers out there and I'd believe it by the build quality I saw. For instance, all of the differentials have a gasket making them truly sealed units. There are also gaskets between the lower gearbox housing and the aluminum chassis. 

Other impressive engineering touches were the rubber boots on all of the shock shafts and the beveled washers located at all of the misalignment joints.

While waiting for my new batteries to arrive I took the time to loctite all the set screws and chassis screws and started on some mods to make the truck more durable. First thing was to make a set of metal CVD sleeves which eliminate the CVD cross pin set screws. Not sure if this is a common failure point on this model but it is on the 1/10th cars I had run in the past.

I then greased the CVD's and then installed some Dynamite rubber boots to keep the grit out.  While I was working on the suspension I also swapped out all of the stock hinge pins for hardened pins available from here. This is probably the only preventative thing that is worth swapping out right away especially if you plan on jumping your MT4.

  Many owners use o-rings or grommets to retain the wheel hex cross pins in case the set screw comes loose.  I chose to go the grommet route due to them being stiffer and readily available at the local Lowe's.

The stock steering servo was replaced with a Savox 1283SG which provides nearly 4 times the torque of the stock unit. Overkill?  Most definitely but after the first run I can say I am more than happy with the servo choice and it is well worth the expense thanks to it's excellent combination of speed and strength. A longer than stock Hot Racing 25 tooth servo horn was also installed to give the servo more of a mechanical advantage.

Holding the car at both ends you do notice a fair bit of flex in the chassis front to rear so I came up with a simple chassis brace to tie the shock towers together. The most common shock loads are going to be from hard landings so a high mounted brace like this is the best option due to the large mechanical advantage it will have when resisting the front or rear ends bending upward (think lever arm).

The electronics and batteries are housed in a two piece tub that is bolted to the center of the chassis. This layout keeps the weight down low which is good but I wasn't too thrilled about the large openings which could allow debris into pinion/spur gears. I am sure the openings are for air flow so I cut some window screen material and glued it to the inside of the tub lid to keep the larger chunks of debris out.  Time will tell if I need to make a small gear cover like the one I did for my previous I10MT.

The stock body is kinda cheesy looking and seemed rather flimsy so I picked up a Pro-Line Baja Bug body (#3238-60) for bashing.  This body is nearly bolt on.  I did have to move the front body mount posts back behind the front shock tower to get them away from the rounded edge on the bug's hood. Most long chassis T-Maxx/E-Revo bodies will fit this car without much effort.

Out back I came up with my own set of body mounting posts which are further outboard than the stock ones to allow me to utilize mounting holes on the flats to either side of the molded engine details on the bug body. 

From what I read the bug bodies tend to crack around the rear mounting holes first so after a layer of gorilla tape I fabricated an aluminum brace to reinforce this area. I have since learned you need to slot these holes front to back to accommodate all the movement possible from bar bracket. With the holes slotted you don't need the reinforcement plate as the body will float. In fact the reinforcement plate makes things worse.

Slot the mounting holes like this. I would do this for any body you mount. Not sure why Thunder Tiger did not do this from the factory since the MT4 mounts are the same ones used on their ST-1 kit which has the rear body mtg. holes slotted out of the box.

I love the extra visibility that LED lights give you both during the day and in low light conditions so LED's were installed in the front bumper and out back in a small mounting plate I made from some aluminum sheet metal.

For batteries I went with a pair of Turnigy 2S 65C 6000mah hard case lipos.  Attached is the included series wiring. The first test run occurred on a local playground with a mix of concrete, sand and dead winter grass driving.  The car handled all surfaces with ease and was amazingly easy to control.  We even did a few test jumps into a sand pit and the car flies very well.  We did have one rear axle pop out of the drive cup early on but I think I may have put the rear camber links in the wrong hole allowing for too much droop. I moved the link in one position and ran the batteries down with no further issues.  An after run inspection revealed a few loose screws which is to be expected.

Update 5-9-12

Not real happy with these batteries.  They puff up during runs a and only take around 5000mah when charged (low voltage cutoff set for 3.4v).  I have cycled a set of Zippy 6000mah 2S lipos as well as some hard case 5000mah 2S Sky lipos and do not have the puffing issues and both sets of batteries take very near their rated capacity when charging (both within 600mah).

 

Speaking of tires, I picked up a some more aggressive looking ones to try in loose terrain.  Would you believe these pre-assembled tires and rims only ran $19 a pair?  You'd think big tires would cost more than their smaller scale counterparts but no, they are half the price of a good set of rubber for a 1/10th scale car. These are the Exceed WC1043's available from Hobbypartz.Com.  They have other tread designs to choose from as well as lower profile versions so you can set your car up for various conditions.

One minor issue cropped up when I picked up a second set of LIPO batteries that did not have recessed battery plugs like the first Turnigy batteries.  I discovered they would not fit in the chassis with either the supplied series wiring harness facing front or rear.  The directions show them setting towards the rear but as you can see the negative plug would stick thru the side of cover.

After some more research it looks like my wiring harness was just soldered wrong from the factory.  By swapping the red and black wires on the ESC connection side you end up with the correct 90 degree configuration on the upper negative bullet connector and straight bullet connector on the positive side. This now matches what is shown on the MT4 webpage. I still had to slightly notch the area next to the rear center driveline to allow the lower bullet connector to clear.

How is it holding up?