TRF419 Lightweight Spool outdrives mod

I have been running the new TRF spool pulley and whilst I have enjoyed the slightly better steering response, the extra 4g weight plays ...

I have been running the new TRF spool pulley and whilst I have enjoyed the slightly better steering response, the extra 4g weight plays on my mind. It's only a small amount of extra rotating mass but obviously I would like to save weight not add it.
Luckily David Joos and Dan Booker reminded me that Tamiya has the parts available to lighten your current TRF spool so let's take a closer look

To do this mod you just need the following parts:
  • 51443 Front Direct Cup
  • 19804389 Direct coupling
These parts were what we used on the TRF417, and they are still easily available.

The current steel 419 spool cups weigh in at approx 11g.

The lightweight components weigh approx 7g lighter. This is because the actual cups are made from hard delrin plastic, which is not as durable but much lighter.

Fit the cups with the pins, then the bearing holders/bearings and try to mount the couplings. You will notice that they are too long and do not fit over the plastic clips at the end of the cups to hold them on.

To ensure you can fit the aluminium couplings easily, there are some modifications that need to be made on the eccentric diff holders. This is because the actual spool is a little wider than the ones used on the 416/7. 

All you need to do is ream out the hole until the alloy cups will spin freely. This is a simple job and you do not have to worry about making the spool unaligned as the bearings are seated and the spool runs through those. You need to ream from both sides of the holder. I took off approx 1mm on each.

Just keep trying to fit the aluminium couplings, take a few more twists with the reamer and repeat. DO NOT try to squeeze it on, as you want them to spin freely. Once the hole is large enough it will clip on and you can easily spin the spool. The final result is a spool that weighs in at approx 18g that is light by any standards, it will be even lighter with the plastic spool (Approx 4g lighter). Although I prefer the way that the car handles with the new spool.

The spool fits perfectly, the wider couplings do not interfere with the lower or upper bulkheads.

Running the new lightweight spool in this configuration has given me the best of both worlds. I still get the improved steering response, now also have the benefit of the car being able to spin up marginally quicker because of the reduced mass. 

This older spool outdrive concept is very strong, I used to run these in Mod back in the day, and they never failed. The internal plastic cups will wear down a over time, but unlike the steel cups the front driveshafts will not wear very much at all. I also prefer the feel of plastic in the spool, I think it just feels a little softer and more stable.  So overall I am very happy with this mod.
TRF419X 4837521691421064121

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