Driving an X-Maxx on water : Our hydroplaning how to guide

We've all seen the videos, a Traxxas X-Maxx tearing along the top of a lake as if it is just driving along a dirt track. It looks absolutely incredible and is a fantastic advert for the truck, but how difficult is it to pull off? We risked drowning our X-Maxx, a friend's X-Maxx and several pairs of shoes trying to find out!

Launching into a lake

Having spent some time watching videos of X-Maxx's pulling this crazy stunt, we took some cursory tips from them, fitted our truck with the official Traxxas sand paddles and headed to a local lake. Despite several different approaches and various throttle positions we sadly failed to get the truck to reliably hydroplane like we had seen online.

The standard truck would run out of steam, cut out and sink, or tram-line into the bank. We couldn't reliably drive our stock model it on the water, nor could our ex-engineer Dan with his lightly upgraded model. So began a project spanning a month of weekends, modifying and testing our X-maxx's till they would reliably perform on the water.

Modifications required

Here are our findings following multiple attempts at walking on water. Each time we failed we headed back to the lab to dry our truck, and for Dan to rebuild it swapping something else out.

Upgraded ESC : 200A

In our opinion the stock ESC doesn't have the capacity for sustained hydroplaning. Neither it seemed, did the Hobbywing Max6 ESC in Dan's upgraded X-Maxx. We swapped both out for Hobbywing's EZrun Max 5 which is capable of a continuous 200A output. The motor wires were extended slightly and XT90 plugs were fitted to the battery leads (more on this later).

Fixing this new ESC to the chassis required a mount to be 3D printed in PLA ,the design available here on thingiverse. Designed specifically for the hobbywing units it fixes to rails on the chassis with a zip-tie and includes a slot for the power button.

Batteries with a burst rate : 75C

The 'standard' batteries are fine for land use but their sustained discharge rate of just 25C wasn't giving the motor and ESC everything it could. Even if you managed to get the truck 'on the plane' the batteries would give out before a lap of the lake was completed.

We switched them out for a pair of Turnigy Graphene Panther's. These beefy 4S 5000mAh batteries have an incredible constant discharge rate of 75C, peaking at 150C! They fit perfectly in the battery tray and as an added bonus they turned out cheaper than the comparable 5000mAh Traxxas 4S. Terminated with an XT90 they could be plugged straight into our newly fitted ESC.

Gearing up : 46T Spur gear

As stock the X-Maxx isnt' slow. Running the stock pinion and spur gear you can easily crack 40mph. Taking advantage of the increased power availability, we opted to up the gearing. Our X-maxx included an optional 46 tooth spur gear refered to as 'speed gear' in the manual.

Removing the standard spur (seen above) with its slipper clutch assembly is fairly straightforward, allowing you to remove the three bolts holding the spur gear on and install the smaller one. Traxxas's helpful reference table also shows you where to remount the motor to ensure the appropriate gear mesh.

Upgraded steering servo

With the truck now powerful enough to sit on-top of the water, the next battle was regaining control. The stock servo wasn't strong enough to rotate the car, even if you backed off of the throttle a touch the force of the water would overpower it and continue to plough the truck straight on. Lifting the throttle further would result in the truck nosing down too hard and sinking.

Traxxas offer a 2085X servo upgrade kit that includes a metal gear servo with 25% more torque, adjustable steering link rod and a heavier-duty spring for the servo saver. This is an upgrade we'd advise anyone to do regardless of them running the truck on water as it really improves the steering performance.

Wheel and tyre change : Sand paddles

An obvious addition and thankfully one of the simpler ones. Traxxas' sand paddles arrive glued to chunky, 17mm mount, 6 spoke wheels with foam inserts already in place.

Use some waterproof tape to cover the holes on the insides of the rims, usually designed to let fluids out. Ignore the comments about cutting notches into the leading edges of the tyres, this is for use on sand and you will want to keep them watertight! Take notice of the direction of rotation for mounting, or the paddles will work against you.

Further waterproofing

Whilst the electronics on the X-Maxx are rated as waterproof, we were concerned that they would not put up with a full submersion in the even of a failed run. Dan removed the lids of the radio boxes on the models and added a thick waterproofing grease to the rubber sealing gasket. He also packed the foam gasket area where the cables enter the box with plenty of grease to reinforce the seal.

The motor was removed from the truck and the end cap lifted, allowing Dan to apply a Corrosion X compound to the rotor, stator and housing to hopefully prevent further deterioration.

Safety net

Lastly, as seen in several other X-Maxx on water videos we added a pool noodle to the inside of the shell. Cheaply purchased from any toy or athletics superstore, we cut down three lengths of this foam and firmly cable tied them to the underside of the shell. When (not if) the car cuts out, you will be glad of this extra buoyancy to stop the truck from completely sinking below the surface!

If you intend to run on a large body of water, we'd also recommend investing in either a dingy or RC boat for recovery. It is infinitely better than waiting for the wind to eventually wash your £1000 RC truck to the shore (ask us how we know).

Securing success : walking on water with the X-Maxx

With the upgrades in place the truck will reliably hydroplane on pretty much any lake we throw it at, but we have compiled a few tips for ensuring success.

Double-check that your LiPo's are fully charged and keep an eye on the clock when out there. The revised ESC is incredible powerful, but it can now drain the batteries faster than ever. On land with a stock setup you are probably used to around 20+ minutes of hard driving time yet on water our new setup will rip through a pair of 5000mAh batteries in a little over three minutes!

Pick a smooth slipway for your entry/exit from the water, the X-Maxx has a reasonable weight balance but sharp drops can see the truck nose into the water or worst case, roll over.Accelerate smoothly up to speed as you enter, we found that at a little over 30mph the truck would sit 'on the plane' quite comfortably, and with our setup we ran between half an two thirds throttle when cruising.

Back off just a touch when turning, that will let the truck level out, allowing the weight over the nose to aide those front wheels to rotate the chassis.

Post run maintenance

The hidden cost of this saga has been the maintenance, not just the cost of parts but the time you need to put into caring for your truck.

It will take you hours, but its important to strip the X-Maxx down to component level to clean it properly. We are talking about a full rebuild over an evening until your hands stink of GT85. Dismantle the diffs and regrease them, relubricate or replace every bearing in the drivetrain and so on. Kev Talbot has produced a great video showing just how much work it takes.

We think it is worth doing it properly to keep your X-Maxx running right so you may even want to remove the bearing seals to clean them out, re-oil them and add some ACF50 to keep them from corroding in the future. To up longevity we actually swapped out the main bearings for ceramic ones at a cost of £160.

Tempted to try it yourself?

If you are new the Traxxas X-maxx, take a look at our review of the truck on land. Should you wish to build a truck to mirror ours, alongside the fluids and 3D printed mounts, you will need the following components mentioned in this article:

• Traxxas X-Maxx 4WD Monster Truck
• Hobbywing Ezrun Max5-v3 Waterproof Speed Controller
• Traxxas 2085X Servo Upgrade Kit
• Traxxas X-Maxx/E-Revo 2.0 Steel Spur Gear 46t 1.0 Metric Pitch
• 2 x Traxxas X-Maxx Paddle Tyres Mounted on Black Wheels
• 2 x Turnigy 5000MAH 4S 75C LiPo Battery XT90

As you can see this isn't for the faint-of-heart, the costs aren't something we'd like to add up, let alone the time put into this project! You may have some success without all of the modifications, but you are also likely to suffer with some heartbreaking cut outs.

Perhaps you have hydroplaned your models with greater success than us? If so we'd love to hear how you pulled it off! Leave us a message in the comments section below!