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Really Quick Bmw 320 Setup

BMW 320 Sideways Group 5

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#1 SlotsNZ

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Posted 31 March 2019 - 01:45 PM

This was in response to someone's problem "elsewhere"
I decided to do a really quick setup of a Sideways 320, to see if I could replicate his problem of the front end lifting out of corners.

To answer the OPs initial question, there is only one chassis design for the BMW 320, code SW320 - it comes as standard SW320/A
(standard) and a more flexible version SW320/A1 (shudder, I fear the flexi-chassis, we want uber-stiff for wood track racing.)

We had a couple of these running in the Group 5 proxy down here last year, - and 3 years back ( I missed the year in-between).
One of them by a known good car builder from Oz was a podiumite at the end of one series. GAS41T?

I can't think of any mechanical/engineering/physics reason why this particular model should exhibit such characteristic, but not
knowing their club/class rules or the surface they are running on, it was hard to comment.

So that set me a challenge. I set one up this afternoon while the wife was out and about. Car is SW58 as below
Posted Image
Basic setup will be stock chassis, 0.5mm offset on the pod, soft braid, maybe a braid spacer or two to ensure full depth guide,
with axle set as high as practical. I'll set up unweighted, then add 8 - 10 grams in my usual places. AW flat-6with no weight in front,
really does need something on all the Group 5 cars to enable sharp acceleration out of corners. We mostly convert to SW here,
then balance them.
I'll use some known wheel tyre sets on the back to save time. - already trued and treated NSR Ultragrips on the back from my M1,
and then swap to some treated Slot.it N22 off another car - that have about the same grip level.

My track surface is smooth wood. Grip is pretty high, though we have a couple of enamel painted tracks around that lock up tighter.

Okay, I did a really quick OOTB setup. 'Scuse the rough video clip didn't want to get too anal on time
and quality of car or video. It took me longer to make the video than it did to roughly tune the car LOL
Pod screws are about 1 turn off tight, the same as the body screws - I forgot to mention that in the video
As it is already doing 5.1 around my track, I would only be hunting about a 0.2 per lap improvement;
so it's reasonable in this quickly set up state - just noisy.
Not sure what the tyres are, they could be an 11mm Ultragrip or a PT1172N22. Slot.it., as they come out
looking and performing about the same after I run them on my softening jig for a few hours.

I used the ones off my orange-bell sidewinder Moby Dick, which is my low powered "nimble" car I use on
short tracks in our racing group; as I couldn't get the hubs from my M1 inside the wheel arches

The body on part - is still an unweighted car.

Further tuning would be step by step, something like this.
  • Soft washers on all screw load points
  • Tinker with the pod looseness, especially the side float screws
  • Check for "click points" - interferences between body and chassis
  • Shift to 1.0mm offset, to lower the back
  • Reduce front tyre diameter to drop the front, as the axle is already near the top of chassis adjustment
  • Maybe add those guide spacers, I haven't used any as yet
  • Coat the fronts, or shift to a zero grip tyre
  • Check body/interior for fully fixed and not flexing
  • Longer body screws to allow more float
  • Mess with gear mesh a little and shut up the noise
  • Perhaps glue the motor to the pod for extra stiffness
  • Tape the underside of the pod to chassis then loosen the pod screws another turn
  • Then start fiddling with weight

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#2 slotmadmac

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Posted 01 April 2019 - 02:23 AM

Good report Mark. Lots of good info here for the newer guys.
Podiums are for short people.

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