And here it is…
I won’t go into too much detail about my build – there are already a lot of very good build blogs on the internet from more experienced TRF owners than me – kentech‘s blog is a great example which. But I will list a few of the things that stood out for me as I put the car together.
- Pinned bulkheads
- Free running transmission
- Low weight
- All the fashionable parts as standard (DCJ’s, floating servo mount etc.)
- Easy to work on
- Generous “Bonus Parts” in first batch
- Quality again
- LiPo mounting system is rudimentary
- Anti-roll bar mounts fiddly
- Fussy about spur gears
- New springs not what I had hoped
- Steering linkage may need a little work if your radio doesn’t have large EPA adjustments
- Not many parts or options available yet
Let’s look at a few things in more detail:
The most obvious change is the Yokomo-style top deck. This style of deck has really taken the TC world by storm and everyone has rushed out their own version of it. Tamiya give you lots of options for connecting the motor mount; there is the single post at the front which the motor mount can be either attached to or left to “float” with the use of a supplied grub screw (not an option that is mentioned in the manual, but one I gleaned from kentech’s blog); and there are screw holes in the top of the layshaft mounts as well, which can be connected with the addition of a 0.5mm shim under the top deck. The motor mount also has four slots to give plenty of options for fitting the motor and avoiding the spur gear – very easy to work on.
The chassis comes with split suspension mounts, a floating servo mount and pinned bulkheads – a feature that I am surprised hasn’t been seen more often since Losi included them on their JRX-S (which was also the first car to have DCJ’s if I remember correctly, 5 years before anyone else took notice). Basically everything you would expect from a car in 2013/14.
The gear diff comes with plastic gears, metal shafts and black o-rings. These give a very free action but not as good a seal as a silicone o-ring. There does seem to have been a small amount of fluid loss through the outdrive since assembly, I’ll have to keep my eye on that. My gut feeling after the shakedown run is that the kit #900 oil (or the #1000 Fastrax oil I built it with) it too free for any conditions and that the rear wheels may “diff-out” too easily. The spool is nicely made with an alloy hub and steel outdrives, which mate to the steel DCJ’s via a blade. The DCJ’s themselves use smaller pins and narrower bearings than usual – Tamiya clearly made the decision to build a compact DCJ that fits within the existing C-hub moulding rather than moulding a new C-hub for a larger DCJ – we’ll see how reliable they prove to be compared to the very substantial parts on the ARC R10 I was running previously.
The spur gear fitting is new, and unfortunately Tamiya have designed it for a spur of around 2.5mm thickness at the mounting. This means that my RW and Kawada gears are slightly too thick to be clipped into place. You can compensate with extra shims on the layshaft but even a small deficit of shimming is magnified and the spurs move around from side to side. I’ve ordered some Panaracer spurs (which are not that easy to get hold of) in the hope that they will be more secure.
I have drawn up a TRF418 gear chart for 48dp. The tooth count range is from 104 to 116, and the largest pinion that will slide in from the side is 37T, although larger ones will fit without fouling the top deck or motor mount – I have put a 43T on there and there was still room to spare.
One detail in the drivetrain that really pleases me is the belt tension. Superficially it’s a trivial thing, but both belts have even tension and are very free in the kit settings – this shows that the dimensions have been thoroughly thought out. Good engineering. The ARC suffered from an overly-tight rear belt which you needed to run on almost the loosest setting – a sign perhaps of how much of the car was copied straight from other designs.
Not that I am implying that the TRF418 design is original. It isn’t in the slightest, it’s a copy of a Yokomo BD7, because that’s the car the European team drivers spent the last year trying to beat. But it is a thoroughly Tamiya-ised copy, refined to the limit.
The car has new suspension mouldings. These are basically copies of the Yokomo parts but I welcome the change, mainly because they have eliminated all the mounting holes that we never use. This means a stronger, simpler and seemingly lighter component. The new steering knuckles only have one hole, and the new rear hubs have a single hole that makes the rear link shorter, akin to the HPI hubs. I would have liked to see a better ball mount for the front anti-roll bar, the 4mm connector is a bit tight, although squashing it with pliers is a handy trick to free it up.
The suspension assembly has the only obvious mistake in the manual, Tamiya suggest putting an extra 0.5mm spacer on each suspension shaft and there is no way the car will go together with them fitted. Take them off and the arms will drop freely, if you need to take out a little more free play, Tamiya make 3mm inside diameter shims that are perfect for the job (#53585).
The anti-roll bars have been revised with a top-adjustable drop link, but the plastic mountings leave a little to be desired, they move around too freely when you are trying to tighten and adjust them. The ARC mounts should fit, they have lips on the edge to locate them on the bulkheads. Roche make an aftermarket one-piece mount that I am tempted to try as well.
Springs and shocks
Tamiya have finally released their own “large diameter” springs – these are basically the same size as the long-popular HPI springs with a 14mm inside diameter and 25mm length. They are finished in a snazzy pearlescent black. So far so good. But they are also close to useless. The kit Black spring (in the middle above) is 1.5mm wire diameter by 7.25 coils – 15-20% softer than an HPI Silver, and about the same rate as the old Tamiya Yellow. The new Red (on the left, and included as a Bonus Part in the first batch of cars) is 1.5mm x 7.75 coils, softer again, and a match for the old Tamiya Red. The new Yellow (on the right) is 1.5mm x 6.50 coils, the same dimensions as a HPI Silver, and it measures up to be about the same rate as the HPI Silver and the old Tamiya Blue. This new Yellow spring might have a place in the pitbox but it is not available as a spare yet so I only have one pair. It will be interesting to see what other spring rates Tamiya release in this new size. It’s also worth mentioning the shocks here, Tamiya endlessly revise the design and the 418 comes with the large diameter lower retainers and also a new spring retainer, as well as clear o-rings and the golden-anodised bodies.
Like many double-bellcrank cars, it can be a pain to get full throw left and right with my radio (a Futaba which only allows up to 120% EPA). I understand why the double bellcrank is favoured but I am not sure it offers any benefit over the single bellcrank used on my old TOP Scythe and Photon, which were a lot easier to set up due to the lever effect. On the 418, I have just about managed to get full lock both ways by using the outer hole on the Tamiya servo saver (18mm c2c) rather than the suggested inner hole (16.5mm c2c). I intend to build up a slightly shorter steering link to get a right angle between the servo horn and said link. This is the setup at the moment:
Tamiya expect you to use an old set of servo mounts to guide the LiPo into place. It’s not a very good solution. I don’t mind the light weight and simplicity, but they obstruct the tape slots. It would be nice to see an alternative to hold the LiPo in place, even if it is as simple as an L-shaped piece that avoids the slots. In the meantime I’ve cut the servo mounts a little to clear most of the slot. The front of the LiPo rests against a screw in the side of the servo mount, but there is also nothing to stop the rear of the LiPo from sliding into the belt and motor shaft. I’ve stuck a piece of plasticard onto the chassis for the time being and we’ll see how well that holds up. Apparently the LiPo mounts from earlier cars will fit into the two spare holes in the chassis, which begs the question of why Tamiya didn’t include the parts in the 418.
Tamiya don’t include a true setup sheet in the kit – so I built it according to my usual basic settings for a touring car. That means standard locations for linkages; 5mm front/ 5.5mm rear ride height; 5.5mm front/4.5mm rear droop; 1.5deg front/ 2.0deg rear camber; and 1deg front toe-out.
I’ve gone for a regular weight Protoform Mazdaspeed 6 shell, the standard choice for carpet racing. Tyres are Sorex 28JB. Electronics are a Team Torke (Intellect) 6500 LiPo at 320gm, Futaba S9550 servo (still going strong after many years), Futaba R603 receiver, LRP Flow ESC (best blinky brakes I’ve tried) and a Vampire 17.5 motor. I have a 40mm fan behind the motor, and with all these components fitted the car is just over 1360gms ready to race – right by the limit without any lightweight parts. The ARC was 50-70gms heavier, which led to me using a shorty LiPO; the Tamiya won’t need one and is a therefore a lot easier to work on. The outdoor tyres are heavier but I should be able to get some weight off with a lightweight shell and maybe a few lightweight screws.
Balance is also very good out of the box, in the region of 49%F/51%R weight distribution and evenly balanced from side to side.
I’ve only ran the car for five minutes on carpet since building. It went straight and went round corners which was about as much as I could expect, although as the grip came in it started to feel quite unpredictable which I think may be a result of the free rear diff and the soft springs. I’ll be trying some heavier oils in the diff and some stiffer springs at it’s next race, the CWIC.
Looks like I didn’t keep the review brief after all…