JRXS Type R Build Guide

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So here we go... although firstly, this isn't a comprehensive list, it's ment to give a feel for what bits need attention when building a JRXS Type-R. Gonna try and keep it in chronological order in terms of the build manual..but I might wander off, lol!!

1. Chassis Prep
First thing to do with any double deck car is to prep the carbon parts. Now, when doing this obviously take pre-cautions when sanding/grinding carbon, the dust produced is very fine, and will get stuck in your lungs... so wear a face mask, some form of eye protection, and ideally do any sanding under a tap so too keep the dust too a minimum.
Sand the edges with a coarse wet and dry paper (240grit), and then use a slightly finer grade (400-600) to smooth all the edges. Now there are two theories on sealing the edges, some people say not to do it as the glue can potentiall tweak the chassis, and others say don't worry about that. I'm in the second camp, so to get nice looking glued edges, clean the sanded edges with some brake cleaner, then run a sharpie marker around them to blacken the surface. Using some thin super-glue, apply it too the surface using some cotton buds (although be a little careful here, as the CA attacks the buds, given off some quite pungent fumes!), running a thin bead around the edges. Leave to dry, and hey presto, good looking shiney carbon edges

In terms of the Type R, the main other area to look at is the area of material under the diff pulleys. With the standard holes, when running the diffs in the low position, the belts will rub on the chassis plate. To fix this, take a dremel sanding wheel, and create a slope off of one edge of the hole in the chassis. The pics below show the front and rear slots having been modified, and the clearance for the front belt after.

Front diff cutout

Rear diff cutout

Belt Clearence

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2. Diff build
One of the unique things about the Type R is it's diffs. The long tube allows it to retain decent length driveshafts and suspension components, whilst still keeping the weight central. The main issue with this is that the central pulley runs directly on the diff tube, and not a bearing. However, there are ways to improve the feel of the diff.

First thing to sand all the diff rings flat. Take some wet and dry sand paper, and sand both sides of the diff rings, with progressively finer grit, up to 1200grit to make a nicely polished surface. Doing both sides helps to ensure the plates are flat. On the diff ring against the copper washer, I also prefer to use a lower grit paper to effectively etch the surface so it grips better.

secondly, replace all the balls in the diff with ceramic versions. Personally I've been using the ceramic balls avaliable from Ghost RC. For the main diff balls, they offer a pack of twelve 3/32" balls as a direct replacement. Replacing the standard thrust balls is also a good idea, as the standard balls with the cage seem to give inconsitent performance, and one of the keys to a good diff is having a thrust race that is best able to transmit the power... so the more balls the better! For this, replacing the standard thrust with ten 1/16" balls seems to make a nice smooth feeling diff, better able to take the loads now produced by modern motors.

When building the diff, use a more sticky greese between the copper washer, diff tube, and diff ring. This helps to grip the diff ring better without slipping. Best greese I've found so far is the Tamiya Hard Friction greese (TAM53176). For the main diff balls, use Schumacher Diff greese (U1301), and on the thrust, Associate Black thrust greese (AS6588) seems to be the ticket

Ceramic balls

Ceramic equipped thrust race

With the diff all built, performing a little work on the eccentric holders can help to free up the drive train. Basically, with the O-ring used to hold the diff in the eccentric, this can tighten up the axle a little, so removing a little bit of material from the inside of the eccentric to let the bearings to sit closer together. This gives a little movement side to side, helping to free up the drive train. Insert a dremel sanding drum into the eccentric, taking care to only remove material from the inside face, and not the outside edges. Two pics below show the modified eccentric holder.

Eccentric sanded

Eccentric modified

One final tip with the eccentrics is to etch the clamping surfaces, this reduces the chances of the eccentric moving during a run. Easiest way to do this is to take a scapel blade, and etch a diamond pattern into the surface. In the picture below, left hand side is unetched, right hand side has been etched.

Eccentric hatching

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3. Bulkheads and drivetrain

Next step in the build is to start bolting the bulkheads to the chassis plate. When doing this, don't tighten up the screw completely to start with, just nip tight for the time being.

Front Bulkheads

Rear bulkheads

Now, with my cars, I differ slightly to the instructions, as I'm using the very nice Flying Fox layshaft and front spool. Ths layshaft uses a screw fit on the front drive pulley, and also allows for the fitment of standard spur gears. The Spool is machined from a single piece of aluminium, and uses two diff outdrives to make a solid feeling unit.

With the layshaft, it really is a case of fit and forget. The only thing to pay attention too is that the screw on the front drive side can work loose, so loctite here is a must. Also, the standard screws are a little long, and if use without any spacers will make contact with the pulley, and possibly even cutting into the belt. Initially I used some 0.7mm spacers to hold the screws out a bit. However i've since discovered that using some 4-40 3/16" screws is a better option, as no spacers are needed

FF Layshaft Left

FF Layshaft Right

With the standard Losi layshaft, it's advisable to make sure that the screws are as flush as possible in the pulleys (possibly ream some material out of the screw hole if needed), and also to remove any mould flash from the surface of the pulleys facing the battery. As space is a little tight, it only takes a small amount of movement for the pulley to touch the battery, adding drag into the drivetrain.

With the FF front spool, one thing to take care of is the screws again. The standard screws are about 0.5mm too long, so make contact with eccentric holder. The two options are to space out the screws (as in the picture below), or simply cut off the excess from the screw with a dremel. If using spacers, take care not to screw them down so the spacer touches the diff outdrive. If they touch, the outdive can compress over the driveshaft introducing a binding spot. You can see in the picture below that the spacers are splayed out slightly from the outdrive. The best option really is to cut down the screws.

FF Spool

With either method, the pulleys need to be modified slightly to allow the screws to sit flat against the pulley, otherwise they will make contact with the covering ridge when being tightened down.

The other option for a spool is to use the Losi Spool pulleys (LOSA3328 for the 41T, LOSA3329 for the 42T). These basically are the same as the diff pulleys, but the balls are replaced with a plastic ring, locked into the diff ball holes. With these spools, make sure that you thoroughly clean all the components to ensure they are clean from any greese. Also, I don't bother greesing the thrust assembly, as effectively it won't need to move when the components are all locked up.
When screwing the spool together, it's advisable to cut the thread in the diff hub, as these can strip if tightened to hard too quickly. Use the diff screw to cut it out of the spool. The final trick to improve the grip of the spool pads, is use some 240 grit wet and dry on the diff rings, creating an etch to grip the plastic when tightened up.
However, despite this, be aware that with high powered mod motors, these pads can still slip, so the only real way to stop this is to epoxy the parts into place... a bit drastic, but a slipping spool can create serious handling issues!

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4. Servo mounting

At this point, | like to mount up the servo before adding the suspension, as it gives a little more room to work
With the servo, select the correct mounts for your servo. If, like me, your using a low profile servo, then you may need to remove some material from the mount on the wire side, as shown below.

Low profile servo modifed mount

Next, loosely put the mounts on the servo, and screw the whole lot onto the car chassis, nice and tight. The servo should be still loose in the mounts however, as the next step is to make sure that bottom of servo is clear of the chassis plate to avoid any potential of it tweaking the car. Place a header card or something similar under the servo, and then do up the screws holding the servo to the mounts. The picture below shows a slightly exagerated setup, but you can clearly see the space under the servo.

Servo mounted

With the servo in place, time to move onto the suspension...

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5. Front Suspension

The main area to pay attention in the front suspension is the region around the C-hub and LCD's.
With the LCD's, follow the instructions, and just take care to remove enough of the heatshirnk. There shouldn't be any overhang of the centre joint, and ideally there should be a slight bevel on heatshink that faces the C-hub. However, even with care on the build of the LCD's, they can still rub on the C-hub at extremes of lock. The only way to solve this is to attack the C-hubs with a dremel, opening up the inside hole a reasonable amount.

Modifying a c-hub

The pictures below show an unmodified hub with a modified one

Modified C-hub on the right

There may be some concern about this mod weakening the C-hub, but so far in running them like this, I've had no issues, and had some big enough crashes to wipe out a few wishbones...

With the hubs dealt with, next job is to build the rest of the components up following the manual, running through the usual checks to make sure nothing is binding, or has excess play.

At this point, I've noticed a couple of inner hinge pins having a lip that stops the suspension ball sliding onto the pin smoothly. To solve, run the lipped edge over some wet and dry at an angle until the ball can slide over freely.

Fixing a hinge pin

Ball sliding freely

One other particular area to also pay attention too is the amount of ply in the front hinge pins. On the two cars I have so far built, both have had 0.3-0.4mm worth of fore and aft play. To remove this, I've used some tamiya 3mm shims, which are avaliable in three different thickness' (TAM53585).

With all the parts together, time to mount it onto the car. Note the kingpin ball joint rather the JR link, with rubber tyres, this just seems to work better, as it gives more camber change on the front. To run a kingpin ball joint, you need LOSA1233 (Kingpin's), LOSA6532 (Turnbuckle), and LOSA6017 (Ball ends).

Front suspension

Mounted to the car

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6. Rear Suspension

The rear end follows a pretty similar pattern to the front. Again just take care to make sure everything moves freely and with no binding.
With the RCD's, I've chosen to use a bit of heatshrink to hold the pin in place, much like the LCD's for the front. Main reason being isI've had a pin cut through a hub once already, and also having lost one completely. Follow the same method for the LCD's, cutting an over length piece of heatshrink, and then cutting it back again once shrunk into place.

Heat shrink on an RCD

Rear suspension ready to go on the car

Rear suspension

As per the front end, again pay attention to the inner hinge pins, and also the arm spacing. The rear arms I've tended to find needs 0.5mm worth of shims to help take out the play.

Rear suspension shims

Note the non-standard rear turnbuckle, this is because the base setup settled on at the moment uses the rear link in the longest position possible. Whilst the standard turnbuckle does reach, there is not a lot of material left in the ball joint, so best to use a longer turnbuckle. Lunsford make a 20mm long link, which still uses the same adjuster as the included Losi links. Part number is L1009 for a pair.

Mounted to the car