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This is odd. I've been doing a lot of test running on a fairly long windy track on the living room floor (arc Pro). Some Fly cars have revealed their shortcomings but, in the main, all digitised cars (n = ~40) run well. The one curious exception is the current DPR Scalextric 911 Porsche (Black/white Le Mans livery, No 88). The pace and track holding are fine - it laps about 500ms better than my Group C slot.it cars. But, unless I really push the throttle, it sticks on the inside corner of my 90 deg 3rd radius curve. (Also outside corner of 90 deg 2nd radius curve). Larger and narrower radii are fine. And when it sticks, I mean it really sticks. Full revs and wheel spinning for 2 to 3 seconds to get it to release. Close inspection at eye level does not reveal where the problem is. I figured it must be bottoming out, but these things have the weight of a feather - that shouldn't jam up like that! I was so puzzled that I bought another 911 - exactly the same one, and swapped the chip. EXACTLY the same problem. In both cars, slot guide is free and easy, gears, axels, wheels all fine and motors amongst the smoothest I have! The integrity of the track looks fine. Has anyone else encountered this weirdness, or know what the solution might be?

Cheers

t.
 

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Discussion Starter · #2 ·
PS - I don't have any other 911s, but other Scalextric GT cars (BMW, Merc, DBR9, McLaren, Viper, Corvette) don't have this problem.
 

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A possible cause of those symptoms is the guide jamming in the slot.

To find out if that is the problem, try gently pushing the unpowered car round the corner by hand you feel the extra resistance where the problem is.

If that's the problem, most likely the guide blade on that car is a tiny amount too wide, although it's just possible it's too deep. If the width is the problem narrowing he front and rear of the guide blade should fix it. (If all you other cars go round OK it's unlikely to be a track problem)
 

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It always amazes me what with interchangeable parts having been around for over 300 years that there are still huge manufacturing tolerances....

What I mean that while all the guides come out of the same factory there can be difference.

The same with the track.

The rails are stamped in by machine and even machines wear out and "wiggle".

I actually had a similar problem with Carrera Go! cars on Sport track. the Go! guide flin (I call call flin because it is longer than a pin but shorter than a flag) is very thick at the bottom, bell shaped as it were.

I used a home-made Dremel (other tools are available9 lathe machine to thin the flin down to the exact same size for all cars.

Nevertheless some cars still stick in the R1 corners (and hairpins) where others did not.

I spent what felt like hours tweaking each car and checking the track to get them to run around without stopping...

So while my experience is because of me modding, there is still a chance that your car is sticking because the guide blade is slightly thicker or a different shape. Maybe it is sitting deeper in the slot because of a stronger magnet, maybe the braids are flatter.

the track may be at fault too. I have a nice flat screwdriver i use to widen the rails at the connection point and I makes sure the tabs holding the pegs are tight. https://www.scalextric.com/uk-en/support/track-maintenance
 

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Living the Life!
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New Scalextric cars have a deeper guide blade, about 1.2mm more than previous ones.

Obvious things to do:

  1. vacuum the slot for debris
  2. check for scuff marks on the guide blade
  3. check width of the slot is adequate
 

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Kevs Racing Bits
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Check the track join, the metal rail can stick proud down in the sides of the slot which can jam the guide.
 

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David H
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I reckon it's caused by guide blades that are a little too thick. In the days before I routinely changed Scalextric guides for something better, I experienced exactly the same problem from time to time.

Given that the issue is with two Porsche 911s and not other cars, it sounds like a batch of 911s was fitted with guides from a batch that was manufactured slightly in excess of the design's thickness tolerance.

I've just measured a handful of unused Scalextric guides and they range in thickness from 1.53mm to 1.90mm. Most are between 1.60mm and 1.80mm, but 1.90mm would definitely bind in a couple of places on my Ninco track and would probably do the same in Scalextric track.

The solution is simple: file the blade thinner.

1.53mm.jpg 1.90mm.jpg
 

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Discussion Starter · #8 ·
Thanks to all. That's a surprisingly large range of thicknesses, Dopamine; nice work. I will examine this more closely tonight. Guide blade thickness does seem a plausible culprit - the odd thing though is how specific it is to the radius of curve - it's fine with a 180 bend of 1st radius curve, so I'm struggling to think how it could be that only intermediate curve radii cause the problem. Weird... I'll try rolling a chassis and guide around the various curves and see if I can spot different reactions to the groove from above...
 

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Kevs Racing Bits
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Does this happen on every bend of same type or the same one(s) every time?
 

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Prof I T
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And when it sticks, I mean it really sticks. Full revs and wheel spinning for 2 to 3 seconds to get it to release.

Cheers

t.
Hi

never a good idea to do the above where digital chips are involved
thumbsup.gif
 

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Does this happen on every bend of same type or the same one(s) every time?
I have only one sequence of 3rd radius that goes through 90 deg...however, I think I have found the solution - it's not the track; but give me a little longer to test and I'll report back...
 

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Discussion Starter · #12 ·
Hi

never a good idea to do the above where digital chips are involved
thumbsup.gif
Yeah - stressing anything on a regular basis is not good practice; I did it once or twice just as part of the diagnosis. Will report back on the therapy soon...
 

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Discussion Starter · #13 ·
Thanks to everyone for your input - I've found the problem and solved it...

1. It wasn't the track (not really) - it was clean, free of debris, free of warping and on a flat surface. On one section one of the metal pieces was sitting a little high at the join. But that was not the root of the problem.

2. It wasn't the guide blades. Perhaps these are a little thick, but by hand, there was plenty of wiggle room in the slot for the guide (on all parts of the track).

3. So I went back to my first guess - that it was bottoming out. As I moved the car by hand, I could 'feel' the resistance at the back end, and the rear wheels stopped turning. This was only around that curve, other curves and straights were fine. So I figured it must be construction of the 911 Chassis. On that car, the crown gear sits so low that the underneath is given a recess in which it sits. This protrudes through the floor of the car. A straight edge across the rear wheels revealed about 0.8mm of space from tyre bottom to that bump. I reasoned that in some cases, the camber (??) of the road coupled with the rise in the metal conductor strips was such that this protuberance was catching; enough to lift the rear wheels from their natural grip. And the angles (wheel base and position of offending hump of plastic) were such that this would be problematic on only certain radii - inner 3rd and outer 2nd, as reported. So I filed down the rear appendage with a needle file (not to the point where I broke through to the crown gear, though I guess it must be pretty thin there now). I did this on both chassis. Both now run perfectly - same smooth motor as before, but now not catching anywhere. Conclusion: there is a deign flaw in the chassis of the 911. Perhaps tolerances are such that this is not always noticed, but there is no doubt in my mind that the fault lies with the car design - not the track (which we must expect to ride up and down a little, owing to its non-rigid construction). Fortunately, the fix takes only five minutes and costs nothing (assuming you have a needle file - or wet and dry).
 

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Discussion Starter · #14 ·
PS - on reflection, it might not be that the crown gear is particularly low, but the chassis of the 911 starts to curve back upwards at the front edge of the rear wheels. In any case, the crown gear won't fit without manufacturer's invention to the chassis floor, and the thickness of that intervention is the cause of the problem.
 

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David H
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Are you running with magnets? They would cause sufficient deflection of the chassis for it to hit the rail at high points.

I ask because I have three of the latest in-line Porsche 911s and don't have an issue with ground clearance on any of them non-mag. That's on Ninco track, which generally isn't as flat as Scalextric Sport. If you're not using magnets and your track is in good condition, I'm surprised that your 911s are grounding.

Mind you, magnets or not, the cars should be sufficiently well designed that there isn't a problem ever. The new range of Scalextric in-line GT cars is great, but ground clearance on all of them has been reduced to a minimum and I can imagine this problem occurring in many households, particularly once tyres have worn down.
 

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Yes - I'm leaving the magnets in. I know this is not cool slot practice, but the project here is to build something big, long, lots of choice in different classes and hold 2 or 3 parties per year. That's it. (Apart from the endless testing and tweaking and fixing and building scenery...) So I need reliability, and easy/fairly quick to grasp performance. I also need to understand what is going under the bonnet etc... (The two 911s had exactly the same weird fault, and were cured in exactly the same way; I'm quite sure it's a design fault that was not picked up during their testing, which didn't properly test the tolerances; there's nothing untoward with my very new track, and the fact that the fault occurred on inner 3rd and outer 2nd alone speaks volumes... During my observations I did notice that the strong downforce was probably having a hand in this. But, mag fan or not, that is the way the cars come out of the box. On tyres: on the first car I did true the tyres and had wondered whether that was responsible for lowering the ride height too far - but on the second (brand new) car that was not the case.)

I agree that the new line of Scalextric GTs look and feel the business - though too fast next to the LMPs for which they should be obstacles; I will do this on each track with controller 5 and 6 on a rubber band - unless anyone can get the app to do a proper job. So I need to find a way to slow them down. As obstacles, that's easy in the digital interface (or a matchstick in the rubber band solution!); but more generally, I think I will look to losing some of the mag downforce in those new GT cars (smaller magnets). Shame, but there we go...

And while we're on it - why-oh-why do some of the Scalextric LMP cars have yellow headlights?
 
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