BRM GROUP C DISCUSSION

[porsche917]

All – Any notes about the upcoming BRM 1/24 scale Group C series should be posted here.

To start this topic off I have attached my story on how to prepare your BRM Group C car.  Enjoy.

BRM Group C Car Set Up How To

[Radial TA]

S-021SS Lightweight Aluminum Wheels/Sponge Tires for Gp.C Cars

BRM Lightweight aluminum wheels with glued & trued sponge tires, for Gp.C cars S-021SS 28.00mm x 15.5mm for BRM 1/24 scale Porsche 962, Sauber C9 Mercedes, Toyota 88C  Minimum size for class legal is 26.5mm

[Radial TA]

BRM 1/24 tuning tutorial shows the brass weight kit for our cars.  132slotcars has the kits.  Do you know if we will need those weights on our track.  I suspect they are more than our track will need for traction and handling if the sponge tires are good.

[BarkingSpyder]

Yeah … that is a ‘goldilocks’ doc – “just right” amount of verbiage – Thanks Marty!

Randy – your point is good – so basically don’t glue in the weights until a few rounds of practice with sponge tires hints that you actually need weights. Some up front or in the center is highly probable (based on experience in Dallas in 2014-15 with these – but that was a longer track with less tricky turns).

[BarkingSpyder]

When will rules be posted?

[ALEREAL3D]

Boiling water ???

read this first:

https://www.google.com/search?q=how+does+salt+alter+the+boiling+point+of+water&rlz=1C1CHZL_enUS726US726&oq=does+salt+aleter+boiling+point&aqs=chrome.2.69i57j0l3.25270j0j8&sourceid=chrome&ie=UTF-8

[Radial TA]

Steve and I were working on my Sauber and discovered the gears are binding somewhere each revolution.  If the offside wheel is moved out a little the mesh is looser and binding stops but the mesh might not be transmitting power fully.  What AW gears are available and will the pinion and gear be spec’d for our series?  I’m seeing only one or two on various sites.

I will wait until we get the motor decision too.

[porsche917]

The rules for BRM, including what gears can be used, have been added to the BRM home page.

[Radial TA]

Where did members get the metal plate for baking the chassis?

[porsche917]

Randy – you can check a local machine shop and see if they have any surfaced metal plate available for sale.  You can usually pick some up for $20-$40.

[Radial TA]

The rules do not include the usual weights must be inside the car or other weighting verbiage.

I also notice three different motors are legal which I take to mean the discussion about some motor being unreliable is not an issue.

[porsche917]

Randy – The rules were updated a couple of days ago to include the verbiage of having the weights inside the car and not visible.

The motors all have different RPM and Torque ratings to I am going to leave those open choice.  The black motor that is in all the newer models will work fine so I wouldn’t worry about changing it.

[porsche917]

The trouble with wheels/tires……….

In spending a couple of hours running the BRM Group C cars today with the goal of “rubbering in” the track I found there was little if any improvement to the cars grip.  I called Alan at 132slotcar to get his input and learned that the BRM wheels/tires I have spec’ed in the rules are a hard compound of foam and will only hook up once the track has many many hours of running.  The Scaleauto ProComp 3 tires we used to run are softer and would hook up better but Scaleauto no longer makes the replacement BRM wheels.  In looking for a suitable option tonight I discovered Scaleauto produces a wheel/tire that is .5mm wider (16mm vs 15.5mm) and 1mm smaller diameter (27.5mm vs. 28.5mm).  Unbelievably, I had mis-ordered a set of these wheels months ago and have them in hand to see just how they will work on the car.  I mounted them to a Porsche, Mercedes and a Toyota and they fit perfect on all three.  The lower profile also allows the car to sit lower in the rear and that can do nothing other than improve the cornering.  I will be taking the cars to the track on Sunday to see how they work.  I will update the forum and change the rules if needed.

[chapracer65]

When the decision to go to foam tires was brought up last year, I appeared to be in the minority in opposing this change.  My criticism was two-fold: first that the change was unnecessary.  We had a problem with Revo Slot tires last year but a different rubber tire could have been chosen. We ran the ScaleAuto cars with rubber tires and they ran fine.  They were slower than other series cars but were controllable and we had no issue with tire wear.

My other criticism with foam tires is one of principal.  I did not participate in the Thingie/wing car racing of the 70’s and 80’s so I have no nostalgia for foam.  My love of scale slot racing is centered on scale.  Regular rubber (and urethane) slot tires correspond quite well to 1:1 tires, even to different tire compounds and grip/wear compromises mirroring their real-life counterparts.  I have never seen foam rubber tires on a real car.  The foam tires are dependent upon tire treatment.  While the “tire cleaner” may not be as messy as other tire goop/glue, it nonetheless leaves dark streaks on the track.  These streaks detract from the scale look of the track (this would be mitigated if the track surface was black).  There is nothing wrong with wing cars, black streaks on the track and super-fast lap speeds but to me this results in a more toy-like sport rather than one based on scale racing.

Now, my above philosophical comments do not address the issue at hand, and I am not recommending a return to real rubber for this series.  The different ScaleAuto wheel/tire may prove to work well enough.  The BRM and RevoSlot foam tire series to be run later this year may well prove to be provide worthy variety for ASCC racing series, as the rally track (and the unlimited Christmas race) already does.  I am merely stating my personal preference for real rubber and true-scale racing.

[Radial TA]

What does this mean?
<ul style=”box-sizing: border-box; overflow-wrap: break-word; color: #444444; font-family: ‘PT Sans’, sans-serif; font-size: 14px;”>
<li style=”box-sizing: border-box; overflow-wrap: break-word;”>The diameter of the rear tires must not be less than <strong style=”box-sizing: border-box; overflow-wrap: break-word;”>5mm at the start of the race.

[porsche917]

I appreciate your input and agree with your points to a degree.  I too never ran wing cars in the 70’s but did run AFX G-Plus cars in the 80’s and they did run foam in their stock configuration.  Having said that, I am not married to foam but the big cars work so much better using them, or at least they did at one time.  We need to figure out what we need to do to get the tires to get some grip.  I will be at the track next Saturday working the problem.  Any and all help would be welcome.

RevoSlot – the tires for RevoSlot were hard to come by and were very inconsistent.  The idea was to move to a foam tire that would be far more consistent, easy to source and equally if not more drive-able.  The other thing is the Scaleauto foam tire is the same width for everyone where the RevoSlot Porsche uses an 8mm rear tire compared to the Marcos 9mm and the Viper/Toyota 10mm.  Now all the cars will run the same 10mm width foam tires.

Realistic Speeds – I don’t think the BRM Group C cars speed will be out of scale, in fact, I believe it will be closer to scale than the other series we run.

The Wear Lines on the Track – The wear lines on the track can be removed after we run the series or we can stick with foam tires moving forward.  A question the club will have to answer.

[BarkingSpyder]

PEANUT GALLERY
— The posted BRM GP-C rules seem to be missing the update regarding the Scaleauto ProComp SC2424p rear wheel tire assemblies. The BRM S-021SS are still spec’ed.
— Sponge/foam tires typically work best with some corresponding product on the track. Remember that when we ran at Dallas the track had a very light glue on it (it was not ‘tire cleaner’) that they also used for sprint races and other 1/24 classes.
— Have the 22-Shore BRM tires (S-020S) been tested? …just asking…
— MOTORS – so Pink has lowest RPM but most TQ (340gm); has anyone tested the Red motor with 212gm TQ – perhaps there would be less fishtails with the lower torque?
— RANDY – it’s ‘rear tires … not less than 27.5mm …’ (1) this happens to be the stock diameter of the SC2424p so the implication is that only basic truing is allowed/or needed (2) a smaller O.D. either by wearing or truing would be a slight advantage from getting the CG lower.

?? TIRE QUESTION – What does this statement mean ‘You are not allowed to true any tires with an angled profile’? I don’t think we have a razor style truer that would make tapered cone shapes possible.
Is this just another Cling-on from the specs inherited from Alan’s series (inherited from Euro rules)?

[porsche917]

Answers to the points brought up above are listed below.

The rules have been updated to show the new rear wheel/tire spec – Scaleauto SC-2424P.

The hard BRM foam tires put down a layer of harder rubber on the track that is difficult for the softer Scaleauto tires to hook up on.  We will be cleaning the track to pull up the hard rubber and put down the softer Scaleauto foam rubber.

I have tried shore 30, shore 22 and shore 15 BRM rubber tires and none of them worked well.

Motors – I personally would not a red motor but I have not actually run one recently.  We did run them in some of our previous BRM series.  Maybe it could work.  I’m not going to try it but its left in the rules in case someone would like to give it a try.

Rear tire specs have been updated.  The minimum rear tire diameter at the start of a race is 26.5mm.

Tire Question – This is not some Euro carry over rule.  This rule exists in many of the series run in the States.  Our truer is not set up for putting a conical shape to the tires but it can easily be done.  The purpose is to have a smaller contact patch for front tires so their is less drag when running the large width wheels/tires.

 

 

[BarkingSpyder]

Thanks for the clarifications Marty! I assume after cleaning the track and the discussions regarding rubber tires the rules may be changing again regarding using ‘rubber’ Shore-30s and perhaps different Max/Min ODs?
BTW – after you left I put on some BRM rubber tires with Pink motor and got some reasonable traction as I added some rubber to the track.

[BarkingSpyder]

BRM rear Wheels S016. S017
S-020 – Rear Tires for Group-C – Standard (30 Shore)
S-022S – Front Tires for Group-C – Lowered
S-019 – Wheel Inserts – BBS 5 Spokes plus Porsche BBS TurboFan covers.

[Radial TA]

Can all of the tire truing machines be set up for the 1/24 wheels?  I used one a few weeks ago that had been set for single tire truing.  I don’t want to waste time trying to figure this out for each machine if not possible.

Are shore 30 rubber tires mandatory, or can we use shore 22 if available and the weather changes drastically?

There is no maximum weight listed, so is that free choice?

[porsche917]

The axle diameter on the 1/24 scale cars is 3mm – just like the RevoSlot’s.  I don’t know which of our truer’s other than the Hudy will work with a 3mm axle.  If you can’t find the 3mm axle for the Hudy you can use your BRM axle as the truer axle.

I would not suggest shore 22 tires.  Think of the added weight of these cars and the acceleration these cars have coming out of the turns.  We run shore 30’s because we have tried 22’s and 15’s in the past only to discover they shred rubber like crazy.  You will be surprised at how much rubber comes off of the 30’s much less the 22’s.  Having said that, you are more than welcome to try them out.  We will allow 22’s and 15’s for those brave enough to run them.

[Author]

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