[Tamar]

Posted 28 February 2019 - 05:22 PM

The Road to Le Mans 1/32: 5 weeks and counting
Just 35 days and we should be on the ferry to Le Mans, yep starting to count days now instead of weeks. As I needed to prep a motor pod for the MK2 chassis for the Ford,
I took some pictures during the process so I could finally make good on a promise I made Dave Maddock some time ago..so here it goes a post on:

 
How to modify a Slot.it SW pod for ballbearings and multiple gear & pinion combinations.
Light, compact and offering great handling, these are the main characteristics why running a Sidewinder motor has become the popular choice for DiSCA spec GT's.
They have but two minor disadvantages that with a bit of handy work are easily to overcome. 
1: You can run but two gear/pinion combinations: 6,5mmø pinion with 18mmø gears or 5,5mmø pinion with 19mmø gears.
With stock gears the lowest gear ratio you can run is 2.38 which means that on the longer straights of some of the DiCSA events your Vmax will be limited as well
2: Due to the close proximity of the rear axle to the motor magnets there is some magnetic drag on the rear axle. 


I'll start with the 2nd issue first:
There are two stock options in the slot.it range that will reduce the magnetic drag, the first being Slot.it's sipa01-54r "reduced centre" axle, which as the picture below shows has
a reduced diameter centre section which provides  more clearance between your motor and the axle. But with it being "just' 54mm wide it can be a bit short.

If you need a wider rear axle your other option would be to use a 55mm Titanium rear axle as available from Scaleauto and Slotingplus.
The advantage (besides them being of a non magnetic alloy) is that they are light, the disadvantage is that they are a bit softer than the hardened steel axles.
Meaning you would prefer to run them in ballbearings rather than the regular slot.it olites. 
For which Slot.it has the ch115 Evo-6 1mm offset motor-pod, which is compatible with their CH105 ballbearings (not included in the kit)

But what if you want to run an other offset? Well then its time you got yourself a set of good drill bits.. a range that starts @ 3,3 mmø going up by 0,10mm to 4,8mmø
 

The procedure is actually very simple: Start with the 3,3mm drill, use the slowest speed setting on your drill and let the drill bit "guide" itself through the rear axle hole towards
the one on the other side. As you repeat this process several times using a 0,1mm bigger drill every time..it does help to switch sides every two or three passes.

 If you're into fine precision tools, you can replace your drill for a reamer to enlarge the openings for the last 2/10th to 4,8mmø (the CH105 ballbearings are a 4,75mmø,
 and if you source them from other brands..that's the diameter you'll be looking for) The next step is to grind away the outer part of the olite holders.
You can grind them perfectly flat with the rest of the pod but I prefer to keep 0,1mm as it will be easier to align the ballbearings later on.
Clean up any burr's left on the pod with the reamer or a sharp knife.
 
 
Room to move..and improve on fixed diameter gear ratios
As I mentioned before, the lowest gear ratio with stock gears is 2.38 which means that on the longer straights of some of the DiCSA events your Vmax will be limited.
If you want to run a lower ratio you'll be looking at different gears & pinions with different dimensions.
So here's a number you should keep in mind: 24,5mm (6,5mmø pinion + 18,0mmø gear)
This is not an exact value of the distance between the pinion and the gear (as there's an overlap etc etc) but its a good value to compare possible other pinion and gear combinations.
For example the Slot.it 14t 7,0mmø Ergal pinion in combination with a Nylon Scaleauto 31t 17,5mmø Sw gear also adds up to 24,5mm. But with a lower ratio (2.24)
If you want to go lower, then you could use the 17,5mmø NSR gears, although you will have to ream these to fit on the titanium axles. But you'll have ratios going down to 2.0 with a 28t gear.

Big pinions, small gears
With a 2.0 ratio you are approaching the limits on what a MX16 small can can accelerate and decelerate on a 72-78gr Slotcar.
But for the long Mulsanne straight a bit of extra top speed might give you that little edge.
For my cars I prefer to use bigger nylon pinions (less weight and better mesh) but even when the sizes of your mixed brand pinion & gear combinations do match, your mesh might still be a bit off.
So below are some images that can show you how you can give your pinion that little bit of wiggle room needed to adjust your mesh.

So what you'll be looking for is grinding tool with a 6,0mmø, what you'll be needing to do is to enlarge the opening in the pod for the Motor bearing by 0,5mm forward and backwards.
Again use the slowest speed possible on your power tool to keep good control of where you're grinding material away.
The next step is to enlarge the openings for the motor screws by the same amount. You can use a power tool, but a plain old fashioned rat-tail file will do the trick just as well (just takes longer) 
As you can see below I also grind away some material of the top of the pod, this is done to make it easier to snap the motor in the pod..and reduces the amount you'll deform the pod by doing so.

I usually wait with aligning the ballbearings till after I've mounted the motor (as this will deform the pod a tiny bit) I use 2 short motor screws to secure the motor.
Best procedure is to use the front screw to adjust the mesh (with axle and gear in place). Tighten it and then remove the gear to be able to insert and tighten the rear screw.
The reason why I prefer to use Torqx screws should be obvious..they don't fall off your screwdriver that easily.

So there you have it, with these mods you'll have an adjustable pod that accepts pinion/gear combinations within a 24 - 25mm range.

With kind regards
Tamar