Build Review: Serpent S400
2007 saw Serpent enter the 1/10th electric touring car market with the S400. With a strong reputation for building top quality, race winning nitro’s I was interested to see how their take on an electric touring car would go. The most recent car I have built is the RC10 TC5 Factory Team so I will be mainly making my comparisons with it throughout this review.
The S400 arrives in a nice compact box with the required documents for the build. The manual features coloured CAD drawings for assembly. Unfortunately there isn’t any tool’s supplied with the kit so you will need your own allen drivers etc. I would also recommend you have a turnbuckle wrench (the Yokomo wrench fits perfectly), some CA glue and thread-lock handy before you start . One thing I would have liked to have seen in the manual was a few more guidance notes. Whilst the drawings are clear there are times when you would like a note to draw your attention to certain things. Other than that the manual is very well laid out. Each page correlates to a bag number in the box, so you always have the correct parts on your desk at each stage of the build.
The first stage of construction is the preparation of the chassis. This involves filing the edges of the battery slots and using CA glue to seal the edges of the chassis. I’ve heard some people say that the chassis material is quite hard and its worth using a good quality file. I used emery paper as I find this is easier to shape the cell slots with and also leaves a nice smooth finish.
Once this is completed its time to start adding parts to the chassis. The manual begins with the rear of the car and the preparation of the wishbones. Its at this stage that I came across the rather curious ball-ends that Serpent have chosen. They involve screwing in a grub screw, and then screwing the ball onto the grub screw itself. I am not quite sure what the benefit of using this system over a normal one piece ball-end is and I am slightly concerned that over time the balls may loosen from the grub screw, but for the meantime they seem to serve their purpose.
Next up is the rear differential. Assembly is very similar to most ball diffs found in touring cars. I have heard stories of the thrust races coming apart so I have purchased a Tamiya thrust race as a spare just in case. The balls are seated into the diff pulley using the supplied differential grease. The grease is supplied in a small pot which can be a bit messy to work with. I would suggest having a cloth handy and using this to smear the grease with rather than a finger tip. The manual suggests using the same differential grease on the thrust race but due to the thick nature of this grease it may be advisable to use the black transmission grease instead which should give more lubrication. Serpent supply a differential adjustment tool with the kit and the Setup Book explains how to set the diff correctly. I set mine so that the pulley only just slipped under force when in the adjustment tool. Once built I was left with a very smooth diff action. I should also mention that the alloy outdrives are very light and well manufactured.
After building the rear diff its time to insert it into the chassis. I used some bearing oil on the supplied bearings before installation. The rear bulkhead which holds the diff fits nicely onto the chassis and all the screws thread easily into the alloy. Although not stated in the manual I would advise using some thread-lock on these screws to make sure they stay in place. Again the quality of the alloy is impressive and I like how the alloy parts are packaged in individual bags to stop them getting marked on other parts while in the box.
A front and rear anti-roll bar (ARB) is supplied with the kit and after installing the diff in the chassis its time to fit the rear ARB. There are two option holes on each wishbone to allow for varying the stiffness of the attached ARB, along with the ability to move the position of the ball joint pivot. Nothing much to write home about here, they are a fairly standard affair and look like they should do the job well.
Final touches for the rear wishbones come with the building and attaching of the CVD’s via. the rear hub carriers. Again the CVD’s are nothing out of the ordinary and go together much the same as most modern touring cars. The rear hub carriers are a lovely example of lightweight alloy and I really like the gunmetal finish they have been given. Plastic blades cover the end of the dogbones and thankfully a few spares are supplied as they seem to be quite easy to break on any touring car I’ve used. I’m generally not a fan of using grub screws to secure hinge pins but it seems to work okay on the rear hub carrier. To complete this stage the turnbuckles are threaded onto the ballcups. The ballcups seem strong and thread fairly easily to the turnbuckle. The turnbuckles themselves are steel and I think at some stage I will be swapping them for the orange aluminium versions. For now however they present no problems and they are easily adjusted with the Yokomo wrench as mentioned earlier.
One area that slowed me down in the building of this kit was the layshaft assembly. The pulleys and spur gear are all secured to the layshaft using grub screws. I do have concerns over this but I hear that with plenty of thread-lock they will stay in place okay. I think it would have been more reliable to use roll pins as in the TC5. Another problem is spur gear wobble. It takes a bit of time and careful work to get the spur gear to run true on the layshaft and I came across a few forum threads about this. Worth noting is that the spur gear supplied is 64 pitch so if you use 48 it might be worth ordering a spur gear along with the kit. I went for a 48dp 78 tooth RW Supalite spur. Due to the low height of the layshaft this size of spur sits quite low into the chassis groove so I wouldn’t like to go much bigger. The RW spur will only allow you to secure it to the spur gear adapter using two screws rather than four due to alignment of the holes.
The alloy motor mount is next up and again this is the same high quality, lightweight alloy found throughout the car. Once again I used thread-lock on the screws going into the alloy mount. The layshaft assembly fits easily into here and spins freely, just remember to fit the front and rear belts before securing down the carbon fibre top plate.
Building the front of the car is much the same as the rear with the exception of the differential. Serpent have supplied a spool for the front in place of a ball diff. This suits me fine as I prefer to run a spool anyway.
Before fitting the carbon fibre top deck the servo saver must be completed along with the bearing belt tensioner. This bearing belt tensioner isn’t adjustable, the belt tension is instead adjusted via. notches in the diff housing which allow you to rotate the differential which in turn increases/decreases tension. It does double as the aerial mount however.
Front ARB is the same as the rear and leads on to building the steering blocks, c-hubs and camber/steering links. Serpent supply 2, 4 and 6 degree c-hubs with the kit with the default being the 4 degree. Its nice to see these extra option parts being given rather than having to purchase them afterwards. One criticism is the securing of the c-hub hinge pin. As with the rear this is done by a grub screw, but unlike the rear the grub screw is going through plastic rather than alloy. This inevitably leads it to stripping the plastic and never tightening correctly on the hinge pin no matter how careful you are. Most other manufacturers have found alternative ways of securing hinge pins and I would rather see the TC5’s method of a button head screw into the wishbone in place here.
Its not often I say this, but the building of the shocks was one of the highlights of this kit. This is partly due to the fact that they are almost fully assembled from the factory, all you have to do is add oil. It is advisable to bathe the foam compensator in oil before assembly. This means than when you add oil to the shock bodies the foam wont soak it up. The shocks are very well made and are easy to fill and bleed via. the bottom of the body. I also like how the springs supplied are all silver with the exception of the very bottom coil which is coloured to denote the rate of the spring. The only concern I have is that the paint is quite thin and if it gets scraped off it might take more than a passing glance to see what springs you are running. Good for keeping the opposition in the dark though! Once completed the shocks are married to the carbon fibre shock towers which allow for plenty of adjustment in shock position front and rear
I think the finished S400 looks very impressive, quality alloy and carbon fibre features throughout and the actual build was very straight forward. I expected this car to be very light, but was surprised when I put it on the scales that it weighed in slightly heavier than the TC5. This could be as a result of the alloy outdrives, alloy rear hubs and steel turnbuckles whereas the TC5 features more plastic components. It would be hard to say without weighing components separately.
The S400 certainly isn’t going to win any prizes for originality or innovation. It doesn’t have a radical design like the JRX-S or Magic E4. But it does have a tried and tested design, one that goes together easily and is easily maintained. I am happy in the knowledge that my batteries will easily mount down one side and my electric’s down the other. I still think the S400 has some room for improvement. I would like to see proper one piece ball ends supplied, roll pins on the layshaft and something other than grub screws to secure the hinge pins. It would be nice to be supplied with titanium or aluminium turnbuckles as well, and I have to say that the supplied Setup Book isn’t very good. It tells you how to make the changes but not what they actually do. These however are really minor gripes and considering this car is in its first incarnation I am excited to see what might be in store further down the line. This is a high quality kit, exactly what I expected from the Dutch manufacturer, and I am really looking forward to testing it on the track!