[woodcote]

This is a return loop for a single-lane hillclimb (or rally track) using one Scalextric Sport Digital pit lane piece as the 'Y' of the loop. I was asked a while back whether it was possible and I thought it probably was... but the only way to find out was to try it!

This is the Scalextric Digital pit lane...

   

The official product costs £54 (£45 at Pendles) and contains entry and exit pieces, plus borders and barriers. The two track pieces (all we need for this project) are often seen for £25-30 split from digital sets - no borders or barriers included. You could try Jadlams. The pit lanes come in right-hand (C7015) and left hand (C7014) versions. The difference is which way the pit entry directs you from the track - to the right or to the left. The entry piece has all the lane-changing electronics installed, plus a moving 'flipper'. The exit piece has no electronics and the flipper is fixed with a metal pin, so its point sits in the centre of the slot. The mouldings for exit and entry pieces are identical - the plastic bits, flipper and rails of the exit piece of a RH set are the same as the entry of the LH set. The electronics of an entry piece can be removed quite easily.

On paper, there are lots of ways of making a return loop with a digital pit exit or entry piece. Here are just two, using the single lane straight (C7016) and curve (C7017) pieces, plus either the inner or outer lanes of Radius 1 curves - two C8202 packs (cut into single lanes) would suffice for the pair of loops...

   

The first obvious thing to notice is that you'll get a short if you attached power to one of these. The loop has to be isolated from the main, single-lane track - and the direction on the main track must change before the car exits the loop. It's fairly basic 'DC' (as opposed to digital) model railway return loop wiring...

   

With the loop isolated and a manual DPDT switch on the main track, I was ready to find out if the pit piece would work as the 'Y' of the loop. The idea was that the fixed flipper on the standard exit piece would allow cars to go straight on, round the loop and then merge back in the other direction...

   

This was the case with most cars - old and new Scalextric, old and new SCX, Ninco S, Teamslot, Policar. I tried a dozen runs of each - a bit of a 'click' with some, but all went straight on and around the loop and - if I remembered to flip the direction switch - they continued back in the opposite direction. If I didn't, the car very gracefully reversed off the track.

However, there were a couple of cars - both Ninco with the older grey guide blade that either hammered into the end of the flipper or went the wrong way down the 'Y' and reversed off the track in the loop. I did have a suspicion this might happen. The guides weren't any fatter or less straight than cars that went straight on, so there wasn't any obvious car fix.

What I did have was an idea to add a spring to the flipper to pull it wide open to oncoming traffic and then let the car exiting the loop slip out...

   

This meant removing the fixing pin, adding a screw to the solenoid socket (which physically moves the flipper on an 'active' entry piece) and then hooking a controller spring round the screw and a piece of brass rod braced between two sockets moulded into the plastic. It worked a treat...



I will be trying slightly softer springs (that one was from an old Scalextric digital controller), but the hard spring did the job very well - no chance of anything catching the end of the flipper and an accelerating car had no problems exiting the loop.

This wasn't just an exercise in curiosity, it is a possible solution to my desire for a track in my office / slot room that goes round two walls, doesn't take up much space, but allows me to experiment with some scenics. All previous plans have failed the space test. This might be possible...

   

And if it is, it will be the subject of its own thread before too long

[Nonfractal]

90 degree u-turn radius 1 curves make me shudder 

[woodcote]

Ha! You'd better stay clear of any slot rally tracks then

   

Stelvio Hillclimb... Radius 1 heaven (hell for Alan), courtesy of Wye Valley.

A quick update on the pit exit 'Y'...

• I tried a few different springs to try and soften the flipper. I found a longer SCX controller spring allowed cars to slip through at much slower speeds. I look forward to when I can safely rummage through the spring bin in a local hardware store. I'm looking for one the same length as the SCX spring, but slightly softer - I think that would be absolutely perfect.
  
• I've ordered a DPDT relay board so I can use a more user-friendly push button to reverse the polarity on the main track. I will add a couple of LEDs in the module to indicate the direction of travel. The relay board will give me the opportunity to explore methods of automatic polarity changes triggered by the car. That needs to be bullet-proof.
  

I set up the full track plan last night, tweaked it to fit the space and did some partial 'laps' (the second loop wasn't isolated, so I left out one piece). I think that track build thread isn't far off...

   

And then I got ahead of myself and started looking at pictures and video (the wonderful VHS Rallies YouTube channel) to start getting inspiration for setting and scenery.

[rallyhub]

Nice report, Andy.
I am very curious how you will perform the automatic polarity changes, controlled by the car itself.

rallyhub

[woodcote]

Thanks Hub! I did spend a few evenings looking at model railway sites and forums to explore the reverse polarity methods they use. The basics are the same, but slot cars do behave differently to trains  - they are much faster and racing cars don't stop at signals! So I shall need to borrow from both model train enthusiasts' and slot car racers' tried-and-tested methods.

Essentially, I will be using standard lap counting devices - dead strip, magnetic reed switches, photosensors or a physical switch in the slot -  to trigger a separate single-channel relay board than will then trigger the reverse polarity DPDT relay board. The important thing is to find something that works with all cars all the time. It might be the manual switch is the only 100% reliable method. I am happy with that (it becomes second nature after a while), but for a public setting an automatic switch will be more important.

However, I'm going to get on and build the track first

[rallyhub]

That sounds very promising.
Success with your experimenting.

Hub

[Top Down]

Is that overkilll? Looks like there's enough space to do away with the pit lane pieces and just use regular straights between the 'rally loops'?

[CMOTD]

Wouldn't a pair of Scalextric PT73 hillclimb/dragster turns do the same job without the reverse polarity mucking about?
   

[Top Down]

I think the slots aren't as deep as Scalextric Sport track, hence looking for alternatives?

[woodcote]

Is that overkilll? Looks like there's enough space to do away with the pit lane pieces and just use regular straights between the 'rally loops'?

Wouldn't a pair of Scalextric PT73 hillclimb/dragster turns do the same job without the reverse polarity mucking about?

Yes to both. However, this experiment came about after someone asked whether the set-up was a single-lane alternative to the traditional PT73-style loop... Specifically, the questioner wanted to build a realistic hillclimb with one narrow track, rather than an unnaturally wide two-lane road. The use of the pit entry/exit piece was their idea. I just tested it out and tweaked it so it works.

In terms of my layout planning, the successful experiment has added to the possibilities I now have. That single lane is certainly going to look good with the scenics - and it does save me exactly half the width of a double-lane track with loops and hugely less space than the two-lane circuit I was originally trying to cram - unsuccessfully -  in that corner of the room. It also tickles my electronic interests...

Brian - if you have a stack of those PT73s in your loft, you can flog 'em for £100-150 a pair these days. For our Rally-Sprint we made our own (see page 26 of the souvenir fanzine here) with standard track pieces - three different designs. In fact, remove the two loops from the pit pieces in the opening post and you have PT73 replacements.

Doug - most of the track I've used is just surplus standard pieces cut down the middle, apart from the C7016 & C7017 pieces in the loops. Most of it comes from my track box - the stuff I don't use in my rug-racing layout and hasn't been absorbed into the WHO/digital stock. The only extras I bought were the two packs of single-lane curves. I could have easily chosen Classic track, using the C8222 classic to Sport adapters around the pit lane pieces. Instead, I wanted the slippery Sport surface.

The single-lane hillclimb loops should be quite easy to do with any track system that has a digital pit lane - SCX, Ninco, Carrera - although the flipper mechanisms aren't identical and will need to be modified slightly differently. Using adapters, the SCX digital pit lane can be inserted into SCX/Scalextric Classic track - and Policar track could be used with adapters around Ninco pit pieces. Eventually, Policar will have their own digital pit lane.

I am sure most people will continue using traditional PT73-style loops with the standard two-lane track, but this is an alternative - should anyone want to try it.