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Dromida 4.18 Mods and Tuning Mega-Reference

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Dromida 4.18 Mods and Tuning Mega-Reference

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Old 02-08-2018, 09:25 PM
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Default Dromida 4.18 Mods and Tuning Mega-Reference

I've collected all the best Dromida tech info I can find, from this forum, other forums now offline, and my own experience.

I hope this can be a starting point for anybody who wants to know about how to get the most out of these great, affordable little cars.

References:
Lots of posts on this forum
http://www.ultimaterc.com/forums/showthread.php?t=202511
http://www.ultimaterc.com/forums/showthread.php?t=216296
Hours of setup, tuning, and bashing
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Last edited by meow_mx; 03-08-2018 at 12:52 PM.
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Old 02-08-2018, 09:26 PM
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Default Suspension Mods

The Dromida suspension design is basic but functional, with good adjustability. It won't work to its potential right out of the box because they have to skip labor-intensive steps to keep the cost down. You can make these improvements yourself to get the Dromida handling its best. Basically, treat it like a kit: begin by disassembling everything and putting it back together more carefully.

Ensure Free Movement
These cars are light, and the springs and shocks are weak. The suspension must move as freely as possible. When you're done, the suspension should flap up and down easily under its own weight, with no shock or tire attached.

Begin by disassembling the suspension: remove the shocks and hinge pin holders, pull out the hinge pins, and remove the hub pivot pins (kingpins).

File the joints: Gently fit each hub carrier into the fork on the end of its control arm. You will probably notice little pieces of excess plastic left on the hub carrier where it fits inside the fork. Sand or file this until it fits inside the fork freely, but without excess play.

Next, use a 5/64" or 2mm drill bit to ream the pin holes. Hold the drill bit in your fingers (don't use a power drill).Gently turn it into and through the holes on the control arm where it attaches to the chassis, and on the hub/hub carrier where it attaches to the control arm. You will probably feel like nothing is happening, but check how the part pivots on the pin before and after. It will swing more freely after.

Finally, ream the upper shock mount pivot. Tightness or binding can prevent the shock from supporting the car's weight appropriately. During reassembly, bolt the upper mount in place first, and ensure it pivots easily. If it turns hard or binds, lightly ream the shock cap with an 11/64" drill bit. Tighten the upper shock mount bolt gently. If you over-tighten the upper mount bolt, it will squish the upper mount bushing, making it fatter and causing binding.

Sanding Hub and Knuckle
The joint where the front hub carrier pivots inside the steering knuckle can also be tight due to extra plastic from the molding process. Undo the pivot screws (kingpins), and if the joint fits tightly, gently sand or file until it fits freely. This will speed the steering response and reduce wear and tear on your servo. You probably don't need to ream this one.

Glue on Lower Shock Caps
The stock plastic shock absorbers have a snap-on lower cap to retain the sealing o-rings. These lower caps can burst off, and then they don't fit tightly anymore, causing them to burst off more easily in the future. One solution is to buy aluminum shocks. To save a bit of money, you can glue the lower caps into place.

While the plastic shocks are brand new and still totally clean, drip a tiny bit of thin CA glue (like tire glue) into the little gaps on either side of the lower cap. It will spread under the lower cap and hold it in place. Don't use too much or you can cause the shaft to bind. This mod prevents you from replacing the o-rings; if they ever wear out, you can feel totally justified buying those aluminum shocks.

Adjustable Front Toe
If you have extra parts available, replace the fixed-length steering links with the adjustable ones. This will allow you to adjust the front toe setting.

Replacement Servo
The stock servo and server saver are adequate, but a better servo can give increased responsiveness and better self-centering. A metal-gear servo is tough enough to run with a horn instead of a servo saver. This eliminates one source of slop from the steering. The TowerPro MG90d (or a clone) fits and performs well.

Secure Brushless Servo Mount
The current style (DIDC1202) brushless servo mount is wobbly, which can make the steering feel sloppy even with an upgraded servo. The short screw is not long enough to screw tightly into the mount, and the screws are not aligned to support the mount against the torque of the servo. Put a piece of servo tape between the mount and chassis, and replace the short screw with a slightly longer one. The usual countersunk Dromida screws are a bit too long, so trim a few millimeters off with a rotary tool or sharp wire cutter.

Hardened Hinge Pins
Especially with the exposed wheels of the buggy and monster truck, the wheel is usually the first part of the car to hit a wall or kerb. This transfers all the crash force into the hinge pin, with the control arm acting as a lever. Dromida stock hinge pins are pretty soft and bend easily. When the hinge pins bend, they stretch and break the control arm and hinge pin holder. After replacing the stock hinge pins with hardened ones, the control arms and hinge pin holders can withstand much more abuse and crashing.

Dromida does not offer upgraded hinge pins, but they are available from industrial supply shops. The hinge pin between the chassis and control arm is 2mm in diameter and about 39mm in length. Grainger industrial supply part #38DT51 is a great upgrade. (#38DT52 should be even better, but I haven't tried them.) The pin between the control arm and hub/knuckle is lightly loaded and unlikely to bend, so you don't need to upgrade that one.

Bump Stops
Small vehicles like the Dromidas have low ground clearance, so they are especially prone to slapping the chassis on the ground when going over bumps or landing from jumps. This upsets the balance of the car and makes it hard to control. You can create bump stops to limit compression travel and prevent the chassis from touching the ground.

Get a few inches of fuel line or aquarium tubing, with an inside diameter big enough to easily slip over the shock shaft. Place the car on a table and push the suspension down until the chassis bottoms out on the table. Cut a piece of tubing slightly (1 or 2mm) longer than the amount of shock shaft you can see. The length should be the same on both sides, though it may differ between front and rear. For each shock, pop off the ball joint, remove the spring seat and spring, hold the shaft in a small locking pliers, and unscrew the ball joint. Slip the tubing over the shaft and reassemble.

Push the car down again and see that the chassis no longer hits the table easily. If the chassis still hits the table, your bump stops are too short and you will need to cut new ones. If the chassis is too high when pushed down all the way, your bump stops are too long. Disassemble the shocks and trim a little bit off the tubing pieces.

If you set your bump stops so the chassis is only 1 to 2mm off the ground at full compression, you will still get occasional chassis slap, but it will be gentler and the car's handling will be upset less. Longer bump stops use up too much suspension travel in my opinion, but might be a good idea if you jump your Dromida a lot.
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Last edited by meow_mx; 02-10-2018 at 08:18 AM. Reason: Improve formatting
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Old 02-08-2018, 09:27 PM
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Default Drivetrain, Motor, and Electronics Mods

Drivetrain mods are basically free speed. Our motors are small and not very powerful, so everything that reduces drag in the drivetrain helps your car go faster and run cooler.

Once the drivetrain is rolling freely, you can bolt in as much extra speed as your heart and wallet can handle!

Bearing Flush and Oil
The bearings Dromida uses aren't special or high-tech, but they're good enough. They come filled with a sticky long-lasting grease that makes the car maintenance-free.

For higher speed and more maintenance, flush all the grease out of the bearings and re-lubricate them with a very light oil such as Dynamite Light Oil or Trinity Royal Oil. You'll have to oil the bearings regularly -- every couple dry-weather runs, and every time the car gets wet.

Use a small container (like an empty tin can) and some solvent (automotive brake cleaner or mineral spirits). Submerge the bearings and swish them around, then take each bearing and rotate it a few turns. Repeat this process until the bearings spin freely when you flick them with your finger, or until they stop getting easier to spin. Lay them out on a towel and let them sit a few minutes so the solvent can evaporate out. Then apply oil around the groove of each bearing a few times, letting it soak in, until the oil starts to come out the other side.

Maintenance is pretty easy with a needle-point oiler. Remove all 4 wheels, and you can access the 8 wheel bearings and 4 differential bearings without further disassembly. Occasionally, remove the spur gear cover to access and oil the motor bearings, spur gear bearing, and rear differential pinion bearing. The front differential pinion bearing is so well-protected that it almost never needs oiling.

Immediately after a wet run, before anything dries out, flush them with a little spritz of WD-40 or something similar. Every single time. Ask me how much fun it is to replace all 8 wheel bearings.

The large Dromida bearings have an 8mm bore, 12mm diameter, and 3.5mm thickness. They are often listed as bearing size code MR128. Stainless steel bearings are available in this size from industrial vendors. It may be a worthwhile upgrade if you live in a wet or snowy area.

Differentials
The differentials have little lips hold the outer race of the bearing on each side. The differential case also holds the outer race of the bearing. The differential spins inside the case, while each part tries to hold the outer race of the bearing... this causes rubbing and a lot of drag.

Cut the lips off, and then file or sand the differential housing if it's not smooth. A sharp utility knife or a Dremel-type rotary tool works great for this job.

You can reduce differential-related drag a little bit further by narrowing it a fraction of a millimeter so it can float side to side. Disassemble the differential and grind or sand the open end of the cup-shaped differential housing just a little bit.

With the bearings oiled and differentials narrowed, they should spin freely in the differential cases.

Dogbone Spacing
Replace the spring in the differential bevel gear output cup with a 2x5mm o-ring like the axles use. This will let the dogbones "float" and find where they fit best. You may need two o-rings on each side in the front to prevent the dogbone from popping out of the axle when the wheels are turned sharply. The car will roll more freely, and the bevel gear output cups, axles, and dogbones will last longer.

Steel Stub Axles
Several folks have reported success using steel pin-type stub axles from the Associated RC18, HPI Mini Recon, or Pro-Pulse. These should last much longer because steel wears better than aluminum or plastic.

RC18 stub axles have a narrow tapered body, and require a 4mm ID x 12mm OD outer wheel bearing. The industrial part number for this size is 608ZZ.

RC18 stub axles are not compatible with Dromida 7mm hex wheels. They require pin-type wheels (such as Associated RC18 wheels) or a pin-to-12mm hex adapter (and standard 12mm hex wheels).

Battery Connector
The Losi Mini-style connectors used in the Dromida cars have high resistance. You can actually feel them get hot! For best performance, solder the brushed motor directly to the wires from the ESC and replace the battery connector with a Deans, XT-30, or other quality connector. This mod noticeably increases top speed and run-time of the brushed Dromida cars. I've never had a brushless car with Losi Mini connectors, but the gains should be similar.

NiMH vs LiPo
The 6S NiMH packs that come with the Dromida cars are decent enough, and if you buy any parts cars from Tower Hobbies scratch-n-dent you will end up with several of them. Go ahead and use them, but invest in a better charger. Even a low-end charger like the Duratrax Onyx 110 will charge the stock NiMH packs much faster and help them last longer too! We have one 4800kv brushless monster truck that we run only on NiMH packs, and it does wheelies, throws rooster tails, and spins donuts just fine.

LiPo batteries give higher performance in a brushless car because their lower ESR (resistance) allows higher current output. The standard size offered by Dromida is 1300mAH, but larger and smaller packs can work also. Packs up to 2200mAH are available that fit in our battery tray. Lighter weight packs can improve handling by equalizing weight distribution, at the expense of shorter run time.

If you have a 2S/3S compatible ESC, LiPo lets you choose your desired performance level by switching between 2S and 3S packs depending on the situation.

Gearing
The Dromida uses ".6 module" metric pinion gears with a 2mm bore. Dromida offers brass pinions with 10, 11, 12, and 13 teeth.

13T is the largest pinion that will fit with M2.5 motor mount screws and unmodified motor mount. M2 mounting screws allow a little more adjustability, usually up to 15T. To fit larger pinions, use a small file to extend the slotted screw hole.

Pinions larger than 13T are hard to find with 2mm bore, but Duratrax Vendetta or other 2.3mm bore pinions fit with a couple turns of aluminum foil wrapped around the motor shaft first. Or, choose a brushless motor with 2.3mm shaft so they fit properly.

Remember that tire diameter changes gearing, too. This is especially important on the touring or rally car because of their little 55mm tires. A touring car with 13T pinion is geared the same as a monster truck with 10T pinion, so for maximum small-tire speed you'll need a really big pinion.

Stock gearing is too high for the brushed monster truck. Switching from 12T to a 10T pinion increased the top speed and battery life. The motor ran cooler, too. Brushless motors are more powerful and can push a 12T pinion just fine.

Brushless Conversion
Converting a brushed Dromida to brushless is pretty easy. Select a 20 or 24mm diameter brushless motor and an 18A to 35A ESC. Almost anything will work, from no-name eBay kits to the Castle Creations Mamba Micro Power System.

To bolt in without modifications, the motor needs to meet these specifications:
2mm motor shaft with a flat spot
M2.5 mounting holes 17mm apart
24mm maximum diameter

In addition to a motor and ESC, you'll also need a receiver and a way to mount the steering servo. The plastic case from the brushed 2-in-1 can be cut up to create a servo mount, or purchase the DIDC1202 Servo Mount. Swap in a receiver compatible with a radio system you already have, or purchase the DIDL1000 receiver to keep using the R2R transmitter.

Many generic brushless kits have M2 mounting holes 16mm apart. These can usually be mounted using extra M2x8mm screws like the front hub steering pivots (kingpins). You may need to lightly file the adjustable mounting slot to get a little more clearance for the slightly closer mounting holes.

Choose a motor and ESC according to your need for speed. The stock motor is a 2040 size, 5300kv unit. Motors around 5000kv are powerful enough for a top speed around 30MPH/50KPH on 2S LiPo. This feels pretty fast, is easy to handle, and won't break parts excessively. Higher kv motors increase power and speed and require more careful suspension setup and maintenance. Speeds up to 60MPH/100KPH are readily possible with 3S power and high KV motors.

Radio Mods
The bundled transmitter D100 has 3 channels on its circuit board, there's just nothing soldered to the "channel 3" input pins. Connecting a 6kOhm center-wiper potentiometer allows you to use the third channel! Depending on what you want to control with the third channel, you may be able to use only a button, such as in the D103 transmitter that came with the Wasteland vehicles.

The circuit board also includes unused solder pads for end point adjustment control of the steering and throttle. More testing is needed to see if these inputs do anything when connected. Please let me know if you have tried it!
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Last edited by meow_mx; 03-08-2018 at 09:28 AM. Reason: Add info about steel stub axles
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Old 02-08-2018, 09:27 PM
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Default Suspension Tuning

Getting the handling right will make your Dromida a lot more fun for bashing. It's the difference in putting power down vs spinning out, landing a jump vs tumbling, and braking in time vs overshooting a corner.

Racers spend considerable effort on suspension tuning, and I'll only be touching on the barest basics here. Search the internet for "Buggy Setup Guide" and you'll find a great introduction to suspension tuning.

Tires
Tires are the most important aspect of getting handling right. All the stock Dromida tires are pretty decent. The biggest struggle is getting them to last until they're worn out -- the hard plastic wheels tend to crack and break from crashing long before the rubber is worn.

The DIDC1135 "square pin block" option tires have good traction on most surfaces, softer flexible wheels that resist cracking, and are lower priced than other Dromida tires. Highly recommended for the buggy and monster truck! They don't fit under the short course truck body without trimming.

Dromida offers the DIDC1144 hex adapter that allows fitting non-Dromida wheels with standard 12mm hexes. Stock Buggy and SC tires are 60mm diameter; Monster Truck tires about 70mm. Look for tires in that range unless you want to alter gearing. 1:10 rally car tires are about right. For speed runs, 1:10 nitro touring car foams should do the job.

The Touring and Rally cars present a special tire challenge because the rear tires are very close to the chassis. Tires even a couple mm wider or taller will rub. Sweep Racing Minis fit the Touring and Rally cars without rubbing. They require the 12mm hex adapter DIDC1144.

Shock Oil
Usually the Dromida cars come out of the box with their shocks half full of very thin oil. It's not adequate. Refill the shocks with good oil, whatever your local hobby shop has in stock. 20 to 40 weight oil is a good starting point: maybe even thicker if you are mostly jumping.

Refilling the shock is easy: Detach the lower ball joint and upper mounting screw, unscrew the top cap, and pour out the oil onto a paper towel or something. Work the piston in and out a few times to get all the oil out. Then fully extend the shock shaft and fill the shock up to about 1mm below the top. Slowly raise and lower the piston a couple times to expel any air bubbles, and top the oil up if necessary. Then screw the top cap back on and reinstall the shock.

Shock Mounting and Spring Rate
Lower shock mounting position changes the effective spring rate by altering how much leverage the wheel has when compressing the spring.

To prevent snap oversteer / spinning out, you need stiffer suspension (higher spring rate) in front than rear. Most Dromidas come with the same spring on all 4 corners, so they make the front stiffer by using the outer lower shock mount. The rear is made softer by using the inner lower shock mount position. (The buggy comes with stiffer front springs.)

If you switch to different springs, keep this in mind. If your springs are the same front and rear, you probably need to keep the front-outer, rear-inner lower shock mount positions like stock. If you fit stiffer springs in front, then start with the same lower mount position front and rear; Tune if necessary.

Upper shock mounting position also has a small effect on the effective spring rate. The inner, more laid-down setting makes the spring feel a little softer. The outer, more upright setting makes it feel a little harder.

The stock springs are soft. If you run at high speed on smooth off-road areas or pavement, you may find the body roll to be excessive with the stock springs. This can be corrected by fitting stiffer springs.

Dromida offers a selection of springs, described in this table:

Code:
Long Springs    Turns   Part #          Rate (lbs/in)   Full Compression (lbs)
Black           8       DIDC1117        2.17            2.92
Orange          9       DIDC1040        1.87            2.45
Blue            10      DIDC1059        1.71            2.25
Stock Silver    10      Stock           1.56            2.10    
Yellow          11      DIDC1038        1.41            1.85
Red             13      DIDC1039        1.20            1.50
Silver BX14 R.  13      Stock           ??              ??      
SilverExtraSoft 14      DIDC1119        ??              ??      

Short Buggy 
Front Springs   Turns   Part #          Rate (lbs/in)   Full Compression (lbs)
Black           8       DIDC1116        2.12            2.58    
Blue            10      DIDC1043        ??              ??      
Stock Silver    10      Stock           ??              ??      
Yellow          11      DIDC1118        ??              ??
Or, you can stretch and trim your stock springs. Spring trimming works because if two springs have the same length and wire, the one with fewer turns is stiffer (higher spring rate). You can approximate the Dromida offerings by counting the number of turns you see in online shop pictures. Stretch your springs proportionally to the number of turns, and then cut them back to original length with a sharp wire cutter.

For example, to stiffen from 10 turns to 7, stretch the spring to about 1.43 times its original length, then cut it to 7 turns, which will be the original length again. Be careful: it's easy to mangle a spring while trying to stretch it.

Alignment
With the suggested modifications, the Dromida suspension can be adjusted for front and rear camber and front toe. These are adjusted by shortening or lengthening the adjustable ball links in the suspension. Shortening the link increases negative camber (top of wheels pointing toward the car) or toe out (front of wheels pointing away from the car); lengthening the link increases positive camber or toe in.

A good starting point is about 2 degrees negative camber front, 0 degrees rear, and 0 front toe. This gives a good balance between stability and cornering on high-traction surfaces.

To slightly increase top speed and on-power steering, reduce rear toe-in by replacing the rear hinge pin holder with a front one. It's about 2mm narrower between the hinge pin holes, which reduces toe-in. Thick spacers will be needed between the hinge pin holder and gearbox; you can harvest them from a broken rear hinge pin holder using a sharp knife.

Differential Oil or Grease
With a powerful brushless powertrain, you might find that the car lifts up an inside tire and "diffs out" when you try to turn under power. A sticky lubricant inside the differential can reduce this excessive transfer of power, similar to a limited slip differential in a 1:1 car. Dromida recommends you grease them with a sticky grease.

The differentials seem like they were designed to be sealed: The outdrives have a lip where they touch the diff case, and a 1mm x 10mm o-ring (aka 10mm ID, 12mm OD) fits on the lip perfectly. I've attached a PDF to print and cut out paper gaskets to go between the diff hoursing and ring gear.

Thicker front oil helps increase on-power steering by helping the front end "drag" the car around the corner. Thinner rear diff oil helps increase on-power steering by making it harder for the rear to "push" the car around the corner.

60,000 weight oil in the front and 20,000 weight oil in the rear is probably a good starting point. I'm currently using 60k in the front and 5k in the rear because it's what I had on-hand, but I think I want to thicken up the rear a bit to put down power better coming out of corners.

Weight Distribution
The stock Dromida is about 70g heavier on the left side than the right because of the battery pack. If you're going to stick with NiMH power, don't worry about it. But if you're switching to LiPo, there's a chance to improve weight distribution.

1000mAH 2S and 700mAH 3S packs are available weighing around 70g, which makes the Dromida almost perfectly balanced. Make spacers from cardboard or plastic to prevent the battery from sliding around in the battery tray. Run time is pretty good with 1000mAH -- 15 to 20 minutes of bashing. The motor and speed control are hot enough that I like to cool them off between packs. With this mod, the car no longer pulls to the left under power.
Attached Files
File Type: pdf
dromida-paper-gasket.pdf (85.3 KB, 44 views)
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Last edited by meow_mx; 03-08-2018 at 12:54 PM. Reason: differential sealing update
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Old 02-08-2018, 09:28 PM
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Default Choosing and Building Your Own Dromida

The Dromida's simple, robust design is a great starting point for modifications. Designing and building a customized Dromida is an inexpensive way to learn about RC car tuning and repair.

I highly recommend a brushless car, either factory or aftermarket conversion. The brushed cars are fun, but the tiny non-replaceable brushes only last a few dozen packs, so you'll chew through motors if you drive a lot. Also, the throttle is much less sensitive; the slowest possible speed is about half as fast as full throttle, which limits the development of your driving skill.

The buggy and monster truck are the best bodies for building a very fast bashing or speed running rig. The monster truck seems to be the best for extreme 50+MPH speeds.

Avoid the short course truck if you want to go fast on pavement -- it gets squirrely above 30MPH. At first I wasn't sure it was the SCT body, but I proved it to myself with back to back runs on the same chassis, switching only the bodyshell. At lower speeds or off-road, this isn't a worry.

The touring car is aerodynamically fine, but the low ground clearance is a problem on rough roads, and it gets worse the faster you go. At stock speeds or on very smooth surfaces, it's great.

Buggy Body Tips
To mount the wing more securely, drill a 2mm hole through the center of the wing and mount (between the mounting posts). Bolt the wing to the mount using a long 2mm screw, one of the thick plastic wing washers, and an extra nylon-locking wheel nut. The original mounting holes and posts prevent the wing from rotating, and the screw makes it strong.

Attach the sides of the body skirt to the sides of the chassis with sticky Velcro. This will keep most dirt and rocks out of your chassis and support the body so it can last longer.

Add a little airflow by cutting a vent. There's small bumps that look like air vents next to the cab on each side. Cut around the front and sides of the right-side "vent" and lift it up a bit to make a real vent. This little bit of airflow can lower motor temps a lot because the buggy body is so tight inside.

Monster Truck Bumper Tip
Put the bumper inside the monster truck bodyshell to reduce cracking at the front wheel wells. When the bumper is outside the body, front-end collisions crush the bumper up into the body and over-flex the hood. Inside the body, the bumper supports the hood so it flexes less.

Hop-Up Parts
The plastic in the Dromida cars is a great choice for bashing: It's strong enough to do the job and flexible enough to resist breaking in crashes. I recommend sticking with mostly plastic parts. The aluminum hop-up parts look great, but they aren't necessary for performance.

I especially recommend keeping the nylon spur gear. They last forever if you keep dirt and sand out of them, and take the damage gracefully if you *do* run them dirty.

I do recommend the aluminum hubs and dogbones, which last much longer than the plastic ones.

Build Ideas
From easy to cutting-edge, here's a few Dromida build ideas to get your imagination going:

Basic: Buy you favorite body style factory brushless from your local hobby shop. While you're there, also get light bearing oil, 30wt shock oil, some 2x5mm o-rings, and a decent NiMH or LiPo battery & charger kit.

Do only the simplest, most effective modifications: flush and oil the bearings, cut off the differential "lips", replace the dogbone springs with o-rings, and properly fill the shocks. Then go have fun, and don't forget to oil your bearings from time to time. You'll enjoy higher speed, better handling, and longer run time.

Cost-Optimized: It's usually possible to build a brushless car for the cost of brushed. Start with a servo mount and a brushed car from the scratch-and-dent section of the Tower Hobbies web page -- preferably one that has a bad motor or ESC. Add an inexpensive 2430 or 2435 brushless motor combo from eBay, a receiver to match your existing radio, built it up with all the mods, and enjoy!

Smooth Power: Carisma and HobbyKing offer sensored motors and ESCs intended for 1:14 applications. Theyíre 24mm diameter and have mounting holes that fit the stock motor mount with minor filing. The sensor allows smoother startups and better low-speed torque if you tune the timing advance appropriately. This should give the best possible combination of all-speeds responsiveness and longer run-time.

Maximum Speedrunner: Folks have reported success mounting a 540-size motor in the Dromida cars by using a mount intended for the WLToys A959. This should give enough torque for huge gearing and top speeds. You'll want stiff springs to support the extra weight and foam or belted tires that won't self-destruct at high RPM. Keep the weight balanced with a heavy battery and/or ballast.

Rocket Powered Dromida: A PWM-input "RC Relay" circuit could remotely trigger a model rocket igniter from receiver channel 3. It's probably a good idea to use NiMH power, unless you can measure the current drawn by the igniter to ensure it won't damage a LiPo battery.
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Last edited by meow_mx; 04-20-2018 at 10:00 PM. Reason: Improve Formatting
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Old 02-09-2018, 10:03 PM
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Please reply with any other tips you have, or criticism / improvements for the tips I've presented. Iíll try to edit the initial posts to keep them up to date with the best info.

Last edited by meow_mx; 02-17-2018 at 08:04 PM.
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Old 02-10-2018, 07:02 PM
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Wow! That's a hell of a lot of info on the dromida! This thread is extremely helpful for doing anything imaginable to the dromida.

I've got a question for you.....

I just slapped on the dromida aluminum shocks and shock tower kit. Seems like the rear has more flex, the front is more stiff. I picked up some 32.5 weight oil but I noticed the shocks were already filled so I just left them alone. The only difference I see is the the front shock position is in the outter hole on the suspension arms and the rear is in the inner hole. Wouldn't think that would make a noticeable difference in stiffness.

Any thoughts?
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Old 02-10-2018, 08:33 PM
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Originally Posted by Beefy nugz View Post
the front shock position is in the outter hole on the suspension arms and the rear is in the inner hole. Wouldn't think that would make a noticeable difference in stiffness.

Any thoughts?
I was surprised at first, too. It makes a huge difference, because the suspension arm is a lever.

Imagine if the shock was mounted at the very end; pushing the wheel would be exactly as hard as pushing the shock and spring. Now imagine if the shock was mounted right in the middle; pushing the wheel would be half as hard as pushing the shock, because the wheel would move twice as far. Of course if the shock was mounted all the way in, it would not do anything at all!

This is how they get the stiffer-in-the-front setup that gives good handling, even though the front and rear springs are the same. The rear feels softer, because it has more leverage to compress the spring.
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Old 02-10-2018, 10:00 PM
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ok, I figured something like this but didn't think that small amount of a gap would make that big of a difference!

i like that way the back feels better. although i am hitting some nice jumps maybe its best to just keep the position of the front shock right where it is.

thanks for your imput
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Old 02-10-2018, 10:18 PM
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something else ill say....

today actually i tried to free up the drivetrain a bit. watched a youtube video about removing those tabs on the diifs that rub against the bearings as you also stated. i feel that my dromida either has a decently mild drag brake (which i don't remember that being an option with my racestar esc) or it has a WHOLE lot of friction in the drivetrain! keep in mind i havnt removed the pinion or anything so the motor is still in the equation. but after pulling my diffs i felt like my bearings were moving pretty freely and not much friction from the tabs. cut them off anyway for safe measure. put her back together and nothing has changed accept now i here what sounds like a tad bit of sand or dirt got in the diff housing lol. still has a lot of drivetrain lag.

the lag is actually so bad, that when i hit a ramp at full throttle the car naturally tilts back like its gonna do a back flip, now heres where normally a slight tap of the break is needed to level out for the landing. not with the dromida, u just let off the throttle and the wheels come to a stop almost instantly, leveling the car out perfectly almost as if you hit the break.
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Old 02-12-2018, 10:35 AM
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The bearings have a fair amount of drag in them with the factory grease, but that's a thing where you gotta decide if you want to be faster with oil or do less maintenance with grease. There's no shame in being lazy with a casual hobby car.

The dogbones can cause moderate drag too, if your ride height is pretty high so that the dogbones are at a sharp angle.

If you want to feel the drivetrain drag with the motor out of the way, I recommend you pull the two countersunk screws that affix the motor mount to the chassis. Then you can pull the motor and put it back in without messing up your pinion mesh.

Another thing you can try is to take more of the car apart, so you can feel the drag of each part or bearing separately. Like, spin each hub separately and feel the drag of each one, spin the driveshaft without the diffs installed, spin the diffs without the driveshaft installed, that sort of thing. It may help you find which part of the car is dragging the most.
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Old 02-13-2018, 06:39 PM
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Thanks again bud. Definitely more in the rear. Ill remove the motor mount and see how she feels and go from there

Anybody know what neutral range does as one of the settings with the esc? Options are 9% 6% 12% and work state.
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Old 02-21-2018, 10:17 PM
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Default Differential sealing update

The differential outdrives have a lip where they touch the diff case. Itís 10mm in diameter and almost 1mm tall. A 1mm x 10mm o-ring (aka 10mm ID, 12mm OD) fits perfectly. I think maybe the diff was designed to be sealed.

I have sealed my diffs with o-rings and paper gaskets, and filled them all the way up with oil. 60k wt in front and 5k wt in the back. It feels really nice right now.

Iíll update after running a while to let everyone know whether this keeps the oil inside the diff or not. I can also post a PDF to print templates for cutting your own paper gaskets.
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Old 02-22-2018, 07:16 AM
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great list to get started
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Old 02-25-2018, 06:23 PM
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Iíve put 2 3s packs and 3 2s packs through the car and the diffs have not leaked noticeably. After some more testing Iíll update the guide.
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