Sunday, November 28, 2010

On Point Racing Damper Tube Conversion for Serpent 120L

Paul Ciccerello from On Point Racing (USA) manufactures specialist parts for the Serpent 120L car including damper tube conversion kits, a dedicated LIPO Chassis and stonger uprated rear pod bulkheads.

Paul can be contacted at

European distribution of Paul's On Point products is via Markus Mobers at Markus is at


It is commonly accepted that link cars have a narrower setup window compared to T-Bar cars. In the move to LIPO power we have pretty much ditched all the T-Bar cars which is a shame. It turns out it is pretty much impossible to end up with a well balanced car with the lipo down one side and the rest of the kit on the other, allowing the T-Bar in the middle. As light as a LIPO is, the rest of the kit is still lighter by some 40 grams. You cannot balance it statically and even with added weight (who wants to do that?) the dynamic balance is lost.... so pretty much every car we now see on the track is a link type.

I think the problem for the Serpent 120L was that the Mono-Shock providing side to side damping was just not working in the Link/Lipo config. Once the natural damping of the T-Bar was removed, we needed more damping from the shock and there was less moment acting on it with the reduced cell weight.

We tried to get more damping by going up in oil weight to 2000 or 3000 CST and beyond in the Mono-Shock. The result I think was a tendency for the oil to "lock" or "pack" in the shock leading to inconsistent handing and the "wheel lifting" we hate in the modern lipo/link era. Also with the Serpent Mono-Shock so low down in the chassis there is very little movement to turn into meaningfull linear damping.

... so ...By the time the 2010 Worlds came along Markus Mobers has already moved away from the Mono-Shock and was sporting a 120L with the familiar damper tube configuration. The damper tube approach holds the damping oil in shear, the damping cannot "pack". The movement generating damping is increased by being further away from the pivot point. We can get more damping with lighter oils.

Waiting for 120L Evo

As I write we are waiting for the Serpent 120L "Evo" which will incorporate this change as standard in the kit. For now I am posting pictures of the On Point Racing conversion on my car which is available now.

On Point Kits

The minimum you will need is the OP101 kit which includes 3 modified pieces of carbon, i.e the bottom and top pod plates and the chassis cross brace.

On Point also supply the OP103 Damper Tube kit (you will need to add balls and ball ends). I used these and added HotBodies balls from a HB12X (having first shortened each ball cup by 4mm).

Paul also makes the OP100 conversion kit that adds a main LIPO only chassis plate (very stiff!) in addition to the OP101 rear bits. This is drilled for a laydown servo (Futaba or JR) and will need the centre pivot assembly from an Associated R5.

Notice the OP chassis has the wider spacing for the R5 pivot. The Serpent part will not fit.

Rebalanced Motor PodThe upper and lower carbon plates move the motor closer to the diff side wheel by 1.5mm. This was a decision made by Markus Mobers I think. The idea is to better balance the pod for BL motors.

What this means is that you are likely to need a shortened outer diff hub to get the axle centred on the pod. I am using the CRC 4227 part for this. Also until Serpent come out with a new rear axle in the Evo car I use the standard IRS axle as the original serpent axle was too short.

Serpent supply the IRS axle as follows:

Now Markus is an LRP modified driver at core. He has balanced the pod perfectly for an LRP/Nosram X12 mod. However, if you run GM motors (Spec or Mod) then correct balance will be achieved by spacing the motor away from the bulkhead by 1mm. If we are going to be pedantic about this, lets be fully pendantic! We could argue it was in the right place in the first place....

 1mm shims used to space GM 10.5 motor away from bulkhead.

Build Details

I have dropped the level of the cross brace by using a pair of shorter ally standoffs from a HB12X. You dont have to do this. In fact I have packed up the outer balls becuase of this. I like a bit more room under the tubes to get the motor sensor wire through.

Also I have drilled out the On Point parts and used some Corally 3mm ally threaded inserts. You need a 4mm drill and a steady hand to do this. Of course you also need some old donor Corally T Bars to raid the studs from.

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