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Hot Bodies Cyclone D4  
Review, part #1   

 A Whirlwind with All-wheel Drive!
Within a recently booming branch of 4wd electric offroad racing, Hot Bodies' Cyclone D4 Ącompetition buggyď is the newest addition to the top of the 4wd buggy class.
With its debut at the worlds warm-up in Japan, 2006, the prototype could claim a victory - so letís see how the production version keeps up!

Hot Bodies Cyclone D4 was officially introduced in February at the Nurnberg Toy Fair, but another few months would pass by until it finally became available to the market. In the run-up to its release, much information, many tips and tricks were available on the net, so one could prepare oneself for the real thing - which is quite exciting, considering Hot Bodiesí many successful competition models. However, this is the first serious attempt at offroad racing, and with the world championships (at the time, writing this review) still ahead, things get even more exciting.

LRP-electronic provided us with a sample of the cyclone D4 for the following review. Please keep in mind, that only a single model has been tested, so the following remarks therefore refer to the test model and cannot be unrestrictedly generalized e.g. due to serial dispersion, especially with measured values.

All-wheel drive 1:10
competition buggy with mid mounted motor and shaft drive


RC-components, ESC, electric motor (540 size), tyres and inserts

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A black box, compact in size and with a distinctive ďD4Ē writing on its top is the home of several well packaged build-steps, which have to be opened according to the manual.
Speaking of the manual, itís at the bottom of the box, right beneath the clear PC-body and the carbon fiber chassis plates. Youíll also find some HPI and LRP newsletters and a supplemental note about how to trim the gear boxes - but more on that for later.

The manual starts with a brief introduction, thanking the customer for choosing the D4 and it goes on with the required rc-components. Remember that this is a kit version, so you have to supply all RC and other electric parts yourself. Not even tyres and inserts are included.
The manual is laid out well, with instructions in English, German, French and Japanese. The individual building steps are clearly arranged and hence easy to follow. 1:1 drawings of screws and other hardware help in finding the correct parts.
 Letís start the build!
The bottom chassis plate, the two upper plates (both 2,5mm) and the shock towers (3,5mm) are CNC cut form carbon fiber. Iíd advise that you sand the edges a bit and seal them with superglue. This prevents the laminate from fraying during offroad-abuse.
When done, the first alloy parts are ready to be mounted according to bag A: The front bulkhead, the motor mount and the rear suspension blocks.

An overview of all carbon fiber parts: Sanding and sealing the edges is mandatory!

The nicely crafted front bulkhead is secured to the chassis with two screws - metric like any other screw on the Cyclone D4. The bulkhead features recessed areas to make the gear boxes sit as low as possible which meets the demand for a low center of gravity. Additionally, the universal joints deflect less this way.

Step B - slipper and servo:
The slipper construction resembles that of other shaft driven mid motor 4wds. Built like a ball diff, with slipper pads instead of the drive rings and balls and lacking the thrust bearing assembly of said diff, the Cyclone D4ís torque limiter is neither adjustable from the outside, nor able to limit the torque for the front end and the rear end independently.
The manual calls for the slipper to be completely locked and the unlocked for a quarter of a turn. Iíd strongly advise that you check this setting and adjust, if necessary as soon as you hit the track. Thread lock is mandatory on the screw that holds the whole slipper together. It prevents accidental loosening.
Afterwards, the servo finds its way into the D4ís slowly growing chassis. This is quite astounding, given the fact that most other manufacturers let you add the servo right before the finish. Hot Bodies decided to take the easier way, providing a hassle-free installation with no parts in the way. Several servo mounts and arms are included for an optimal adaptation of any brand.
The Cyclone D4's slipper construction loosely resembles that of a ball dif.
Due to the square-cut interlocking protrusion and a missing thrust bearing, the slipper is neither adjustable from the outside, nor able to limit the torque for the front end and the rear end independently.

In order to set the slipper, only the four screws of the top plate have to be removed whicht means quick access to the slipper. (see the picture below)

Step C - ball diffs and center shafts: Building the center universal shafts was a breeze. Everything went together just fine. Only the grub screw, which secures the universal joint, is a bit difficult to reach.
Be sure to add thread lock as the instructions tell, but abandon the supplied grease. Grease and dust from the track make up a good grinding paste, so the universals would wear out fast.
The ball diffs are identically built for both ends. You should clean all ball diff parts with brake cleaner, since they are covered with an oily residue to prevent corrosion.
In the first days of the Cyclone D4ís release, the ball diffs got a bit infamous for their weak 2mm screw that would not hold up to its task. It works fine for me (more on that in the second part) but Hot Bodies quickly updated the new kits with a 2,5mm hex screw.
Speaking of the screw head, the slotted head of the 2mm screw is a bit awkward to hold with a screw driver, hence putting the two diff halves together may be a bit tricky.
To overcome this, simply stick a piece of paper towel into the outdrives, so the inner assembly canít fall off when you put one half beside.
The assembly is completed by setting the correct tension on the diff screw: You should not or hardly be able to turn the crown gear as you lock both outdrives (with scissors or allen wrenches). Generally speaking, the front diff should be a little bit more locked than the rear diff, so that you feel more resistance turning an outdrive while holding the crown gear.
Remember to readjust the diff setting after a few minutes of track time, since the parts break in and loosen up a little.
The ball diffs are identically built for both ends.
Crown and pinion gears leave quite a sturdy impression.

The power distribution to both ends is carried out with the help of alloy universal joints that are directly joined to the pinion gear shafts.
Step D - drive train, shock towers and steering:
As soon as the diffs and center joints are completed, the gear boxes can be finished. A little addendum states, that itís possible for the crown gear to hit the upper gearbox cover and hence some sanding may be needed. This however was not the case with our review sample, as the gear spun pretty smooth with the box closed.
Shimming the gears is vital to the performance and durability of the drive train. A gear mesh between the crown and pinion gear, which is too loose will quickly wear them down. Setting the mesh too tight creates unnecessary strain on the motor. However, with plastic gears it is always recommended to set the gear mesh a little bit on the tight side with only a minimal amount of play. Hot Bodies therefore includes some shims, though it wouldnít hurt if theyíd include some more.
Speaking of the correct gear mesh: The upper gearbox has additional bracing molded on the inside opposite to the shock tower mounts. This is a nice idea since it gives the gearbox additional strength and keeps the gears perfectly align even if the shock towers face high loads.
Another thing that makes sure the gears stay aligned properly are small pins and recessed areas around the screw holes that key the parts together.

As soon as the gear boxes are sealed, the shock towers are ready to mount.
The ball studs which carry the upper camber lonks are attached to seperate blocks which are themselves secured to the gear box with two screws.
Like with the gearbox-halves, pins and recesses key the involved parts togehter and take the load from the threads.

(Click on the picture for an enlarged view!)

Slowly, the individual parts begin to form a handsome offroad-chassis ...
Iím especially fond of the Cyclone D4ís steering system, which is sturdy and almost free of any backlash. You should be aware though, not to tighten the screws too much as this will bind the steering. Little pegs on the steering arms tilt the steering plate a bit and preload the bearings which takes out any play.
As soon as the two upper plates join the gearboxes with the center mount, Step D is completed and we can move on to the Cyclone D4ís suspension.

(Click on the picture for an enlarged view!)

Step E - the front suspension:
The layout of the front suspension loosely resembles the current crop of 4wd buggies. Itís a new take on the classic Losi suspension, where the wider steering knuckle clamps the c-hub. But with Hot Bodiesí racer, the kingpins are threaded into the c-hubs instead of the steering knuckles. The concept creates a bigger bearing surface, but on the other hand, it creates higher loads on the threads. With alloy c-hubs, this would be the better choice, but with plastics involved, I like Team Losi's idea better.

Itís a good choice from Hot Bodies, to drop the dreaded suspension e-clips in favor of grub screws and suspension pins with a flat section for the screw to hold onto. But thereís a risk in confusing the 3x3mm grub screws reserved for the suspension with the 3x2,5mm screws for the universal joints. I did! So letís put it this way: the silver screws go into the c-hubs and the black screws secure the universal joints.
The front bulkhead gets plastic inserts to avoid wear. Putting everything together was easy and noting had to be trimmed or shimmed. The front arms have very little play and move freely up and down.
The kit includes in interesting tool to make building the camber links easier: your trusty 4-way wrench is equipped with a plastic insert that captures the ball end. You donít have to use your universal pliers here - no risk scratching or damaging the ball cups!

Step F - the rear suspension: A conspicuous number of shims get to use as we move on to the rear suspension. Not only that, but they come in various sizes, 5mm and 6mm in diameter with a thickness of 0,5mm, 0,75mm and 1mm. This may result in a multitude of setup options, but distinguishing and arranging them is not really fun - to put it in a polite way.
Like with the front suspension, the out hinge pins are secured with silver grub screws. The inner hinge pins again rest in plastic inserts to prevent wear on the nicely crafted alloy suspension blocks.

Front and rear end for comparison - to simplify matters, the shocks are also attached, though I'll cover their build in the next paragraph. (Click on the pictures to see an enlarged view)
The kit includes an anti-roll bar for the rear end. It is again secured with a grub screw that should be tightened slowly until the anti-roll bar can only move a little.

Step G and H - the shock absorbers: The Cyclone D4ís shocks are made from alloy and feature a three piece design similar to Kyoshos latest 4wd and 2wd racing buggies. To make building the shocks easy, the appropriate tool is included.
The spring preload which controls the ground clearance is adjusted with a knurled nut. The o-rings are easily accessible thanks to a threaded end cap on the sealing cartridge. The upper shock cap features a thin o-ring and should be mounted very carefully.

The picture above makes the three-piece design obvious. The purple colored knurled nut offers quick access to the shocks' o rings which are covered with a white plastic tube that doubles as a guide for the shock shaft.
Speaking of the internals, the shock shaft has two threaded ends, so the shock piston is not secured with e-clips, but with a nut instead, which makes setup-changes in this department easier. The shocks are filled from below without any problems, just like any shock loosely based on Team Losiís design. A small cut in the sidewall of the alloy cartridge simplifies bleeding the excessive oil.
The shocksí standard kit-setup should prove itself in the following test runs. Itís a worthy base for further fine-tuning.

Let's use the remaining space for some criticism: The kit did not include silicone oil for the shocks. It would have been nice if Hot Bodies included at least a bottle of 30wt which the manual calls for, as a base setup!

Step I - the finish line:
As weíve attached the servo really early in the build, only the Rx, Esc and motor remain. The Cyclone D4ís chassis is really slim, so I stuck the Rx on the motor side to make room for the typically larger brushless-controller.
Due to the wide cutouts in the chassis plate, the batteries can be mounted in two different positions thus giving some room to adjust the chassis balance.

(Click on the picture for an enlarged view!)

12mm hex rims are included in the kit. Mounting standard Losi-wheels is no problem. Youíll only need the original Team Losi hex adapter, or Hot Bodiesí version with the part no. 61499.
After cutting and painting the polycarbonate body, under tray and both front and rear wings, weíre ready for the first roll-out!
A short resumť to summarize the build: Short, because everything went together just fine! With the Cyclone D4, Hot Bodies has concieved a fantastic buggy. Of course, some folks will exclaim "COPY!" due to obvious similarities, but Hot Bodies just did it right and paired up the best 4wd offroad chassis layout with a capable suspension and refined it with some new ideas.
The steering system is sturdy well constructed, and demonstrates, that there are alternatives to shiny alloy.
The kit is well equipped for a competition offroader, so you can easily stay away from the tuning stuff for the first few races. (But you may add a front oneway instead of the diff)
With an MSRP of 419,90 Euros, LRP seems to hit just the right price tag, as the Cyclone D4 is placed just a little below the main competitor.

Written by Florian Klemm
Translation and pictures by Aaron Banovics
This article has been published by on 9-9-2007.