TOPIC: Blakbird's 58519 Bruiser Build

Blakbird's 58519 Bruiser Build 3 months 2 days ago #51384

I started building Tamiya's only a little over a year ago, and I built and documented before I discovered this and other forums existed. The following is my build journal of the Bruiser re-re which was the first 1/10 Tamiya I built (I like to start big) from my web site . Larger versions of all the photos can be found there. If you find that I make some statements indicating I didn't know what I was talking about, please remember this was my first!
Tamiya released the Bruiser in August of 1985 and, at the time, it was an absolute revolution. All metal chassis, 3-speed transmission, oil filled shocks, 4WD with shifting transfer case, real leaf springs, this model had it all. The problem was that it also cost 39,000¥ or $350 at the current exchange rate, perhaps twice that much adjusted for inflation. That put it completely out of reach for most kids. But in March of 2012, 27 years later, Tamiya re-released this classic this time at 89,800¥. So it wasn't any cheaper than before, but the people who wanted it had grown up and had more money now. The updated model replaced the old 750 sized motor with a more moderate 540 and also updated the transmission considerably. Of course the old mechanical speed controller was replaced with an ESC, but other than that this model is much like it was decades ago.

I managed to get a hold of one in 2017 and couldn't have been happier with the build. This is pretty complex assembly project with loads of metal, hundreds of fasteners, plenty of painting, and anything else you could want out of an RC project. The final model is a bit hard to categorize. It is certainly a scale model and uses a hard body rendition of an RN36 type Toyota Hilux. The tires are obviously much larger than stock, and the suspension is considerably lifted as well. The finished model is certainly not fast, but neither is it a crawler. It is not a monster truck, so what is it? I don't know, it's just awesome. It is a scale cruiser and works great on pavement, on grass, or on the trail. With open front and rear differentials the off road performance isn't great even in 4WD. You can lock the differentials manually, but then it is no good on road. I used anti-wear grease in the diffs for a happy medium. The 3-speed transmission is really the star of the show and shifts on the fly. Multiple speeds are not strictly necessary with electric, but it makes low speed crawling quite pleasant and high gear is fun on the road. With leaf springs and fat tires, this thing bounces around plenty. As of this writing many upgrades are available and I installed plenty of them. I used relatively inexpensive analog Futaba servos and the stock ESC, but I replaced the silver can 540 motor with a moderate brushless motor. I also added lots of lights and some additional interior details. Battery space is limited so a 7.2V NiMH works best. You can read about the whole experience in my build journal below.

The Bruiser has quite an impressive box. It is big and heavy with retro box art. Sadly, I did not take any pictures of the inside of the box. Everything inside is nicely arranged with some blister packaging highlighting key parts. I flattened the cover and saved it because I may frame it some day. This model is too special to just discard the packaging.
There is a lot of hardware inside. There are 5 bags labelled A-E which contain the bulk of the fasteners and loose metal parts. Others are contained in a blister pack in the box. I emptied the hardware from each bag into a separate slot in my plastic case so I could access everything more easily. The huge pile of metal bushings you see are actually from the King Hauler, not from this model. The Bruiser comes with full ball bearings.
Step 1 starts right out with the frame rails and connects them will all metal cross members. Since virtually this entire kit is metal, using thread lock is very important. The kit includes some red gel type thread lock, enough to do the whole model. It works a little differently than regular blue liquid thread lock, but is actually easier to apply in my opinion. The second step starts adding brackets for the upper shock mounts.
Steps 3 and 4 add shackles for the leaf springs and a crank arm for the steering. At this point the only plastic part is that white steering crank. Keep that in mind for later, because it is really the only weak link on the model and is not nearly stiff enough to properly control the steering. It is made from the same very soft frangible plastic as the bumpers (and the other white parts). You can see the rubber grommets at the top of the damper stays which will cushion impacts. This model is full of little details like that.
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Blakbird's 58519 Bruiser Build 3 months 2 days ago #51387

Time to build the differentials. Step 5 attaches bearings and stub axles to the 13 tooth metal pinion gears. The gears appear to be cast alloy rather than machined which makes them weaker than they could be but still stronger than plastic.
The model uses gear differentials, but not your standard bevel gear type. These are planetary differentials using only spur gears. The left picture shows the first layer which is an output sun mating with 3 planets. The planet axles are locked to the housing making it the planet carrier. The right hand picture shows the second layer which is another set of planets and the opposite side sun gear. The two layers do not connect together with gear teeth, rather they are connected by using the same housing as a planet carrier.
The 24 tooth ring gears are integral to the housings. When the housing spins, the planet carriers follow along. As long as no wheels are slipping, the planets do not rotate. If one wheel slips, the orbit of the planets allows the sun gears, which output to the axles, to spin independently. Awesome system.
Now the rear axle. We start with a pair of splined steel shafts and add some aluminum support collars, ball bearings, and E-clips. The axle housing is cast aluminum as well and holds the axles, differential, and pinion. I was a little worried about how thin the wall of the axle housing is, but it has been no problem at all. Just make sure not to over tighten the screws.
The front axle is a bit different because it has to steer. The basic construction of the internals is the same, but instead of ending in splined shafts the axles end in dog bones beneath a spherical hub. The second image shows the steering knuckles and output stub axles installed. In both images you can see an open hole above the differential. This is an access point to install a grub screw which locks the differential. It is really nice that you can lock and unlock the diffs, however this hole faces upward and is therefore not accessible once the axle assemblies are mounted, so it is best to decide now which way you want to go. I started by leaving the diffs unlocked but found once I finished that the off road traction was poor so I went back and locked them. Then I found that the steering was poor. As a compromise, I went back the third time and used Tamiya anti-wear grease to semi-lock them and I think that is the best choice.

Blakbird's 58519 Bruiser Build 3 months 2 days ago #51388

Nice tuto. I love that.

Blakbird's 58519 Bruiser Build 3 months 2 days ago #51390

Step 10 opens hardware bag B and begins assembly of the suspension. We start with the leaf springs, each of which uses 3 stacked leaves. Nothing makes a better scale truck than real metal leaf springs. Next the springs are connected to the axles. This is actually a bit tricky because the axle housings can rotate in the saddle clamps until everything is tightened. You need to get them oriented correctly so the inputs will face the right direction to accept the drive shafts. The angles are shown in the instructions, but you have to eyeball them and then try to hold everything in place while you tighten. The manual says to use "synthetic rubber cement" here. I didn't know what that meant so I used CA which was a problem because then nothing can be adjusted. Turns out that you can use Shoe-Goo which I highly recommend. This will stay pliable so you can make adjustments. This step also adds only the second set of plastic parts which are the shock mounts. You can buy metal versions from RC4WD and if I were doing it again I would probably get them but they are difficult to retrofit because you have to do all the adjustments again. To be fair, I've had no problem with the plastic. Metal is just cooler. If you don't understand why then you shouldn't buy this kit.
Now it is time to install the axles on the frame and make this look like a chassis. The rear suspension uses a pair of long trailing arms to stabilize the leaf springs and carry thrust loads. The front axle just bolts directly to the springs. There is no panhard rod, so steering forces get transmitted to the springs.
The shock absorbers are quite unusual. They are oil filled, but they are not sprung. They act only as dampers for the leaf springs. The main piston does not have any holes in it, instead is has flat spots on the side to allow for fluid passage. The piston is retained with E-clips. After filling the shock, you add a second floating piston which has an o-ring seal. This replaces a bladder for volume compensation and floats up and down with shock stroke. There's a nice rubber boot which protects the main rod seals from contamination.
Once the head ends are installed the shocks are complete. There are no rod ends. The rod threads directly into the damper stays on the chassis.

Step 15 builds the highly unusual wheel hubs. No hexes here. The stub axles have flats which drive the hubs, and the wheels actually bolt onto the hubs with 3 screws.
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Blakbird's 58519 Bruiser Build 3 months 1 day ago #51403

I really like this build log :y:

Bruiser is one that I have allways wanted, but is still not part of my collection.

Blakbird's 58519 Bruiser Build 3 months 1 day ago #51409

Now the dampers and wheel hubs are added to the chassis. Note the unusual inverted damper arrangement and the lack of rod ends. The left image shows the rear axle and the right image shows the front with protective skid plate.
After Step 17 the rolling chassis is complete. Pretty much everything you see here is metal and it is glorious. There are no weak links here, you can grab it anywhere and shake it around and everything stays well together.
The 3-speed transmission is a thing of great beauty. I expected that it would be pretty much the same as the 3-speed in the King Hauler, but that's not true at all. This is a completely unique beast, and actually much more complicated than the newer King Hauler. The housings are cast aluminum, and the build starts in Step 18 with the installation of a pair of spur gears rolling on bearings. The screw protruding from the end cap is used to support the transmission. The two gears in the second image are not part of the system to change gear ratios, but rather drive the transfer case. This transmission is only four wheel drive in first gear, so these gears are connected to the lowest gear on the main shaft.
Once the first two housing sections are bolted together, the transmission looks like this.
Next comes the build of the main shaft. The parts shown in the left hand image are the driving rings. The darker parts are keyed to the shaft. The lighter aluminum collars slide along the drive rings and engage floating gears. The right hand image shows the completed main shaft. There are 3 gears: a 30 tooth, a 27 tooth, and a 22 tooth. Each floats on bearings and does not engage the shaft unless the collars grab them. The 22 tooth gear drives the transfer case and does not control ratio changes.
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Blakbird's 58519 Bruiser Build 3 months 1 day ago #51410

The shift forks contain the magic. You can't simply translate both shift forks at the same time. This would engage multiple gears and jam the transmission. You would expect to need 3 shift forks for a 3-speed, so how do you do it with only 2? The answer is the little raceway for the balls that drive the shift forks. The C-shaped dark part in the left hand image contains the raceway. Each shift fork has a hole for a ball. When the balls are in a raceway detent they can stand proud of the forks which then slide along the axle (which is driven by a servo) When the raceway drives a ball into a detent in the rod, the fork is pushed to follow the rod. It is really hard to describe and just as hard to figure out even when you have the parts right in front of you, so the picture on the right might help. This is an excerpt from Step 20 of the manual which shows the balls, the forks, the rod, and the raceway.

Note the plastic "shoes" on the shift forks which help to minimize friction as the driving rings rotate beneath them. The kit comes with extras for when these wear out.
Now the shift rod assembly needs to be mated to the main shaft and the pair needs to be carefully inserted into the housing. There is a rectangular support for the raceway which keeps it aligned with the shift rod.
Next is the secondary shaft. Like the main shaft this has 3 gears on it, but unlike the main shaft these are all locked to the axle. We have 14 teeth, 17 teeth, and 21 teeth here. All three gears control ratio changes, but the largest does not mate with anything on the main shaft. It's mating gear comes in Step 22 below.
The first stage of the gearbox is this planetary system. The big output gear is connected to the planet carrier and has 23 teeth. Each of the 3 planet gears has 20 teeth. The planetary assembly is inserted into the gearbox housing where the 23 tooth output gear mates with the last gear of the secondary shaft.

Blakbird's 58519 Bruiser Build 3 months 1 day ago #51411

In case it wasn't complicated enough yet, now we get to add a plastic 59 tooth ring gear to mate with the orbiting planets. The 70 tooth spur gear has an integral 19 tooth sun gear for driving the planets. The final step in building the transmission is to attach the motor and 19 tooth pinion. Phew!
This path through this gearbox is about as convoluted as they come, but luckily Step 35 in the manual is not a step at all but an explanation of the torque path through the gearbox, shown below. With this assistance of this picture, we should be able to derive all the final gear ratios. Let's break the problem into parts:
  • Motor Ratio = 70:19 = 3.684:1
  • Planetary Ratio = 1+(59/19) = 4.105:1
  • 1st Gear = 21:23 x 30:14 = 1.957:1
  • 2nd Gear = 21:23 x 27:17 = 1.450:1
  • 3rd Gear = 1:1 (Note that 3rd gear goes straight through and doesn't use the secondary shaft at all)
  • Transfer Case = 22:15:22 = 1:1
  • Differential = 24:13 = 1.846:1
Therefore final drives are:
  • 1st Gear = 3.684 x 4.105 x 1.957 x 1.846 = 54.6:1
  • 2nd Gear = 3.684 x 4.105 x 1.450 x 1.846 = 40.5:1
  • 3rd Gear = 3.684 x 4.105 x 1 x 1.846 = 27.9:1
I am happy to report that I did this entire exercise without first looking at the picture on the box and I got the same answers!
If we compare the 3-speed transmission in the Bruiser with the 3-speed transmission in a 1/14th scale tractor truck, we can see the significant differences. They both have two axles, but the Bruiser has 2 shift forks while the tractor has 3. The tractor transmission uses driving dogs which make it easy to shift gears at any speed. The Bruiser driving rings need to be synchronized to allow the lobes to slip into place, so sometimes it takes a moment to shift or even refuses until the right RPM is reached. The Bruiser has the additional function of engaging the transfer case in first gear and freewheeling in other gears. Finally, only the Bruiser has the cool planetary reduction. With all this extra complexity probably comes less reliability, but so far I have had no problems with either. The Bruiser version is quite a challenge to build and get right though. It took me a couple of tries to get everything lined up correctly .
Just for fun we can look back at the original Bruiser transmission from 1983 and see that it is significantly different. Besides using a 750 sized motor, is also lacks the planetary reduction and uses 3 shift forks.
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Blakbird's 58519 Bruiser Build 3 months 1 day ago #51412

Step 25 installs the drive shafts onto the gearbox. The drive shaft and u-joints are really nice steel units which allow a bit of telescopic motion. The instructions tell you to put some CA glue on the E-clips of the u-joints but I ignored this advice and paid the price later when one fell off. Follow the instructions.
Step 26 installs the gearbox in the chassis. The mounting system is very clever. The whole assembly just slips into a pair of rubber grommets which act as vibration isolators. This makes it fairly easy to remove. At this point, nothing is stopping us from hooking up the electronics and firing up the motor, so of course that's what I did. At this point the transmission is locked in 2nd gear, but you can actually drive around on the wheel hubs to try it out.
Steps 27 and 28 have you test wire the electronics. I started out with a Tamiya TBLE-02s controller and a 5000mAh NiMH battery along with a Spektrum 3 channel receiver. Step 29 installs the servos into the electronics box. I used a Futaba S3305 for steering because it has good torque but a cheap HiTec HS-425BB was good enough for shifting. The servos face downward when installed on the chassis. The electronics box does a reasonably good job of protecting everything from contamination or water, but is not completely sealed.
Because the electronics box is located on the back of the chassis, we need long linkages to reach the steering and shifting balls. The kit comes with two high torque servo savers which use metal springs. The rods exit the electronics box through an opening which is sealed with a rubber flap.
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Blakbird's 58519 Bruiser Build 3 months 1 day ago #51413

Now we flip the electronics box over and install the ESC, the receiver, and the power switch. Because the box is so far back, both the battery wire and the motor wires need extensions which are included with the kit.
Now the electronics box is installed in the chassis and the wires are connected. Some of the screws and washers are a little tricky to get to here. Once installed, we can hook up the other end of the ball end links for steering and shifting. Now is also a good time to adjust the lengths and make sure the steering is straight at neutral and the 3 shift positions work. I highly recommend using a programmable radio which allows assigning a switch for shifting and adjusting the end points. This is much easier than using a 2-stick radio with shifting on the left stick as the instructions recommend.
Next the tray for the battery is installed. The battery sits in the tray and is held with rubber bands. Then the white plastic bumpers are installed as well as the triangular body support above the motor.
The final step in getting this thing rolling is installing the wheels and tires. There is really no reason to glue the tires, and the instructions do not tell you to do so. The tread is directional though, so make sure you get it facing the right way on each side of the vehicle. The tires are quite stiff and there are no foams.
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