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6 Years after: CanAm proxy car post mortem

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  • 6 Years after: CanAm proxy car post mortem

    We are all supposed to learn from history and a good opportunity just recently presented itself to me. Bear with me as I roll back the years....

    In 2011, a young..., OK, OK, make that "less old".. me entered a car in the P class of the CanAm proxy. It was one of those "what the heck: let's give it a shot" type of entries. It was prompted by my huge appreciation of how well a basic stock Fly Ford GT40 ran on Luf's Targa at that stage. So my (naive/optimistic/stupid: take your pick....) thought was: let's enter an essentially stock Fly GT40 in the premier class in what was THE premier proxy at the time and see what happens.

    Sad to say this was no Cinderella story: I entered an essentially stock Fly against some incredible machines and as was expected: I got slaughtered! By just about every car in every class! Like ending 56th out of 64 entries: all but one of the GT class cars and most of the GTU cars beat my sad little GT40.

    The shame of it!

    But here we are 6 years later: a sadder but wiser...., no, that's not right: a still happy and hopefully somewhat wiser me ran my ex-proxy GT40 at our regular races a couple weeks ago. And strangely enough it was not all that bad! So that led to some soul searching: why was it so horrendous in 2011? What have I learned since then? What can I do simply to make it better and see where it ends up?

    As a baseline: when I ran it two Fridays ago, I was able to turn a 6.846 second lap. THat is pretty darned quick actually: as fellow club member Duke (Duke777 on this board) mentioned in one of his recent posts: not very many people end up under 7 seconds on Luf's track. So a sub-6.9 second lap is pretty good. But...

    BUT

    I could do some quick laps. But in between those things were hairy: it was just hard to get it around the track consistently quickly. At the time I did mention that my car had too much motor: after I drove it in the Targa leg in 2011 I wrote "Even at 10V, the 23k MBSlot Krahs motor in my car was a handful at the Targa. Admittedly the Targa is probably about as twisty as you will get in an series but still: 10V is pretty mild. The annoying thing is that I have repeatedly voiced the "handling before horsepower" principle to some of my local fellow slotters: seems I am not good at listening to myself..."

    But there were clearly some other maladies as it would just unexpectedly deslot too often to be a halfway decent proxy car. I am quite sure that numerous deslots during the proxy was likley what killed it then.

    So I have just started taking it apart and looked with my more jaundiced eyes at the car to see what was wrong and what can I do to improve it. Initial thoughts:
    • It is just WAY too high! It is approximately 2.5mm off the track. What WAS I thinking?
    • The front tyres are clearly out of round and sharp at the edges.
    • The front tyres are way too grippy.
    • Even though I put a piece of styrene tubing under the front axle and I did attempt to get it straight, the front axle is not aligned properly: the one wheel is cocked in the air.
    • Braid is way too stiff
    • Glued the motor with hot melt glue: it sort of feels like gelatine at the moment. It might have dampened motor movement but it sure as heck would not have stopped any movement.
    • The chassis flexes in all kinds of axes: will have to attend to that.


    Those just at first glance. I will look at it more closely and start fixing the ills: will report as I progress and see how it ends up!

    Alwyn

  • #2
    Love these type of reviews. Can't wait to see the progress and mathematical equations regarding efficiency.

    Comment


    • #3
      Progress!

      All right, this is beginning to look better!

      For perspective, perhaps I need to clarify what I had done to the car initially to “prepare” it for the proxy. And I put the word “prepare” in quotation marks because the level of preparation was rather suspect.

      I chose the car for the proxy because, bone stock, it was such a nice smooth, quiet and reasonably quick runner. Not hugely fast but just NICE. But clearly the motor was woefully weak to compete in the CanAm proxy, so I added an MB Slot Krahs 23k motor. Glued the motor in place with some (useless!) silicone adhesive.

      And I thought the very least I should do was to put on metal rear wheels with decent urethanes glued & trued. At the same time I replaced the rear bushings with Sloting Plus RSS Victors bushings. These are very nice because they allow for slight misalignment with the spherical bushings in a Teflon holder. But I must say over time I have come to be suspicious of them in terms of rigidity and control of chatter.

      I also replaced the guide with a Slot.it guide and placed a piece of styrene tubing under the front axle to remove the “flop” that it had.

      And other than some body float that was it.

      What is probably more important than what I did was what I did NOT do! I started out with a sweet running, low powered slot car. And ended up with an overpowered, uncomfortable to drive car. I did not add weight. I did not brace anything. I did not replace the (what turned out to be somewhat wonky) front wheels. I did not true the front tyres. Overall, the front end setup was woeful, and in the recent past I have come to the conclusion that a proper front end setup is very nearly as important as the rear if you want a decent slot car.

      So fast forward to 2017 and my attempt at redeeming the very, very unsuccessful 2011 entrant:

      1. Started with a bit of an inspection: something that I missed initially was the fact that there was quite a lot of chassis/motor to body interference. One more thing to remedy.

      2. Next step: taking everything apart and cleaning: a proxy series takes its toll....

      3. On second look it turns out that the glue holding (and I use that word politely!) the motor in place was actually an extremely weak silicone sealant. Cleaned all of it off as far as possible.

      4. Looked at the rear wheels/tyres: the car had some wide BWA wheels on the back. With the hub removed, these allow the hub of the spur gear to sit inside the wheel, thereby allowing wider wheels and tyres. BWA wheels used to come without any external indication of where the grub screw is, so normally I mark the position of the grub screw on the inside of the wheel because, once the tyres are glued you have no way of finding the grub screws. Small problem: I did not do it on one of the wheels of this car! This was enough of an excuse for me to decide to rip off the old tyres and put on a clean, new set of urethanes. I had a pair of Paul Gage 20137LM's on hand: these fit the BWA wide wheels beautifully! Not only that: man, do they look MEAN from behind! Like real, wide Ford GT40 tyres!

      5. Chassis bracing: ended up adding three pieces of brass square tubing: one down the length of the chassis in the middle and one on either side from the motor to the rear axle area. While I did not notice any chattering the last time I ran the car, I did note some chatter when we ran the car in the proxy leg at Luf’s Targa in 2011. So better safe than sorry: brace it and be done!

      6. I had put a shim between the chassis and the guide when I installed the Slot.it guide. Seeing as the car was running way too high I pulled this out.

      7. Started working on truing the front tyres…. And found that the wheels were just hopelessly out of round. So I decided to ditch the plastic wheels and put in a pair of 15 x 8 CB Design insert wheels. Added some NSR 19 x 10 zero grip tyres. Trued and profiled them and coated with clear nail varnish. Polished to suit.

      8. Cut off the front axle holders and glued on some SCC adjustable axle holders.

      9. Put on some new, clean soft NSR braid.

      10. Started fettling the interior of the car to remove all chassis/motor clashes with the body.

      So most of the work is pretty much done. What is left is to true the rear tyres, put everything together, add some weight and generally set it up properly. Then some oil and grease and off to the track!

      So far so good...

      Alwyn

      Comment


      • #4
        Now you tell us !

        10 years ago, when I got back into slots , I devoured information from people here including you - after all, you guys OBVIOUSLY know what you are doing.

        Now I find out you are merely mortal like me - and discover all the same shortcomings a few years down the track, just like me.

        Comment


        • #5
          Originally posted by SlotsNZ View Post
          10 years ago, when I got back into slots , I devoured information from people here including you - after all, you guys OBVIOUSLY know what you are doing.

          Now I find out you are merely mortal like me - and discover all the same shortcomings a few years down the track, just like me.
          Hey, I am not going to defend the indefensible: the car was bad: period! But then I did enter it on "let's try it and see" basis with a stock, unmodified Fly chassis.

          On top of that I am clearly a slow learner: the following year I entered a Fly Porsche 908 with not much more changes to it! But at least I did some stuff better: ended 10th out of the 23 P class cars that year!

          But on the other hand: this car somehow still did a 6.8 second lap on Luf's Targa a couple of weeks ago. I am not sure what changed but that is pretty quick. Not sure how quick it will be after all this work: will have to wait and see!

          Comment


          • #6
            Eagerly waiting on what you can reap from the rebuild!

            Comment


            • #7
              Any findings, tips, and help is much appreciated. Thanks in advance!

              Rob

              Comment


              • #8
                Done!

                OK, the actual work is done. Not having a track at home means I will have to wait until Friday to actually test it.

                Some pictures:



                And what is clear in this picture is that I need to do some more polishing of particularly the right rear tyre.



                The need for polishing the right rear is very evident in this image:





                This picture shows that it is now quite a bit lower: almost looking like an NSR's height....



                Suspension detail and exhausts got lost in the proxy: clearly was an exhausting series... But how about them fat tyres on the rear....





                Comparison image to a stock Fly GT40 (only urethanes added):



                It is a touch porky: with the added weight plus the bracing etc. it now weighs in at 90.7g compared to the stock GT40's 73.9g. Will have to see if I should perhaps replace the two pieces of lead in front with just one.

                Really looking forward to running it on Friday. When working on cars I am always tending to stick my neck out on predicting lap times without the car having turned a wheel: great way to potentially look very foolish indeed. With this one I must say I would be disappointed if I cannot get below 6.6 seconds. This would put it in a heady category of rather fast cars. Best laps to date on Luf's NEW Targa:



                Admittedly this is with only about a quarter of my cars timed on the new track, but still....

                Alwyn

                Comment


                • #9
                  Looks the business Alwyn, should go good!

                  Thoughts (I get them sometimes no matter what people say) ... 14 grams of weight does seem on the high side, would probably be more spry on half that maybe? Are those rear bushings free of any axle play, and also 'one with' the motor in terms of creating a rigid drivetrain? To my mind, that's more important than how much the rest of the chassis may be flexing. I see you've used spacers on the rear axle, and I'm a great believer in doing that just for the sake of smoothness (two real thin ones is better than one regular thin one, if you get my drift) - how about the front axle (I like that axle tube and the axle blocks), when it comes to friction the same thing applies, though it's less critical than the rear. And of course, nobody's more critical than me heh heh ...

                  Comment


                  • #10
                    Good to hear from you Paul! Comments as per your comments:

                    Originally posted by Wet Coast Racer View Post
                    14 grams of weight does seem on the high side, would probably be more spry on half that maybe?
                    Those wheel weights are actually cut pretty much in half. Maybe a bit more than half each, so the total weight is likely around 8 - 9g, not 14g.

                    Originally posted by Wet Coast Racer View Post
                    Are those rear bushings free of any axle play, and also 'one with' the motor in terms of creating a rigid drivetrain? To my mind, that's more important than how much the rest of the chassis may be flexing.
                    Regarding play: I pulled on the axle in all directions to see if I could discern play: there was none that I could find. Now I did mention that I am somewhat suspicious of the Sloting Plus bushings so if I find even a HINT of movement/chatter when I test the car... out they go!

                    Drivetrain rigidity: If you look carefully (bit difficult with the way the pictures are taken) you will see white epoxy along the outside of the chassis at the back by the motor/rear wheels. The epoxy actually covers 1/16th inch brass square tubing (same stuff you can see running down the middle of the chassis in front of the motor) that runs from in front of the motor to behind the rear axle. If that flexes, I REALLY have too much horsepower in there....

                    Originally posted by Wet Coast Racer View Post
                    I see you've used spacers on the rear axle, and I'm a great believer in doing that just for the sake of smoothness (two real thin ones is better than one regular thin one, if you get my drift) - how about the front axle (I like that axle tube and the axle blocks), when it comes to friction the same thing applies, though it's less critical than the rear.
                    I used thin SCC teflon (maybe nylon?) spacers on both front and rear axles to get the appropriate front and rear track. I actually stacked up like 5 spacers on each side outboard of the front axle blocks: you can see the whole shebang if you look closely. And BTW: no front axle tube: that is an optical illusion. Just a regular Slot.it axle cut to length. The grub screws that come with the SCC axle blocks have nice rounded tips so the friction is reasonable.

                    Originally posted by Wet Coast Racer View Post
                    Thoughts (I get them sometimes no matter what people say) ...
                    .
                    .
                    And of course, nobody's more critical than me heh heh ...
                    People can be so cruel....

                    Cheers

                    Alwyn

                    Comment


                    • #11
                      My bet?

                      I must say I would be disappointed if I cannot get below 6.6 seconds. This would put it in a heady category of rather fast cars.
                      6.45

                      Anybody else?

                      Comment


                      • #12
                        Originally posted by Wet Coast Racer View Post
                        6.45

                        Anybody else?
                        Um, thanks for the vote of confidence Paul, but I fear you might be rather excessively optimistic.

                        For some perspective:

                        * I think most of us recognise that the North America Gp. 5 proxy probably has just about the best 1/32 scale slot car performers around.
                        * The Capri IN FOURTH POSITION on my list of fast cars with a lap time of 6.422 seconds is the car I have been preparing for the next round (2018) of the NA Gp. 5 proxy.
                        * For testing purposes I took it to Chris's (F1Fan) track when we ran the last round of the 2017 NA Gp. 5 proxy on his track.
                        * At that time I was able to do pretty much the same lap times as the podium finishers in that race with the Capri.

                        Ergo and by inference: you are expecting this lowly Ford GT40 to turn almost the same lap time as the Capri, which turned basically the same lap times as the leaders of just about the fastest proxy around?

                        While I am one of the world's natural optimists: you're on! Five bucks says I do not get under 6.55 seconds!

                        Alwyn

                        Comment


                        • #13
                          Right, then.

                          I can imagine your angst when you pick up the controller!

                          Comment


                          • #14
                            Good job Alwyn !!!......I am sure it will run well

                            I hope you don't mind, but, there are a couple of things worth mentioning that you may find beneficial in your next build.

                            1/ Longitudinal stiffening of practically every plastic car chassis is a good thing as most are too soft on this plane which results in "axle tramping". The symptoms are similar to a chassis that is torsionally too soft..."chatter", but, are generally noticed under acceleration and braking. Often while accelerating out of a corner, this axle tramping can occur, and it can be misdiagnosed as "chatter" which is generally the result of a chassis that is too soft torsionally.
                            The good news is that it is generally difficult to make a chassis too stiff on a longitudinal plane.....so stiffening is a very good idea.
                            While it appears that you have addressed this issue with your mods., the use of brass is not the best choice, as it has no real memory, and has a tendency to bend (and stay bent).......which is not the hot ticket for consistent/fast handling.
                            You should strongly consider using some piano wire (.055 will be perfect) as it has a strong memory, flexes evenly, and as such will offer much improved dampening.

                            Below is a pic. of a little piano wire bracket that I quickly made to act as an example..........it is the wrong length for this chassis, but should illustrated the point. There is no need to glue the full length of the wire, just the brass tabs to the motor can/chassis front.......this will allow the center piano wire rail to provide progressive flex on both longitudinal and torsional planes.



                            2/ The Sloting plus bushings with the nylon housings are OK, but, OK at best..........the nylon housings do flex, and this flex can allow the inner brass bushing surfaces to move and create alignment issues.........all "self aligning" bushings require a small gap between the housing and actual bushing in order to function, and this gap, no matter how small introduces movement (slop) into the mechanism, and although minute, it is still there, and not a good thing. You will never see a "self aligning" bushing/bearing on any high end/high performance slot car for this reason.
                            Additionally, the nylon casings do not accept glue very well at all, making gluing them in a bit of a waste....in and area that is very critical to be rigid.
                            You would be much further ahead to use some single flanged sintered bronze commercial grade bushings from Prof. Mtr., PCH, SCC, etc etc. These are much better quality than most of the traditional plastic car manufacturer units, and being sintered, hold oil much better. As an added bonus, these are less expensive that everything else.

                            3/ I cannot see from your chassis pic. if you have done the following, but, I will mention it nonetheless........Most plastic chassis, and most definitely the FLY chassis have inadequate guide rotation, which manifests itself as broken guide blades and broken guide tongues!!. As most are races as designed (with magnets) guide rotation is not an issue as the car is usually well out of the slot before any sliding occurs.......sans magnets,...well, a whole new ball game, as frequently big slip angle slides do occur,..the front of the guide hits the chassis stop, and well, either the guide blade can shear or, the post breaks.

                            There is a simple fix that you can do to all your non mag cars that will prevent chassis/guide damage/breakages.........I have done many many cars for both myself/friends/customers with no issues.

                            The following few pics. outline the process.......I use a dremel with a round diamond bit, but I have also used, round files, exactos', etc.etc.

                            Whille this mod. will not make your car faster (unless you like to drive with tank slapper slides at every corner), it will protect the hard work you have done on the rest of your chassis, and will eliminate the need to buy additional chassis.

                            This will not weaken the guide tongue!!!!....by allowing the guide to rotate without hammering on the "stops", you will eliminate the stress in this area and,.......no more guide/chassis breaks !!!

                            The first pic. is of a stock fly chassis/guide.......very little guide rotation!!



                            Remove the guide, and mark a "U" shaped area to be removed



                            Remove the plastic with a round file, dremel (careful !!) etc.



                            The guide now has considerably more rotation!!



                            Cheers
                            Chris Walker
                            Last edited by chrisguyw; 09-09-2017, 06:34 AM.

                            Comment


                            • #15
                              Great work so far.

                              A couple notes of my own that your excellent write up has brought up in my mind. When it comes to piano wire one thing I like to do is experiment with different lengths and positioning of piano wire. I don't epoxy the wire down immediately I use a thin viscosity CA glue I can easily crack off later and reposition or if I'm satisfied I will do a final epoxy. The tires are nice and wide on that fat wide Ford body, sometimes I find the slightly narrower 8 to 10 mm wide tire will give me more grip on a wider car versus narrow. Narrow tires I stick with Supergrips...wide tires I use Ultragrips because the the increased pressure on a narrower tire and decreased pressure on a wide tire. I love the eraser analogy of pushing an eraser on its side versus the flat side.

                              My thoughts of course are worth maybe two pennies! So take them for what they are worth!

                              Rob
                              Last edited by cgyracer; 09-05-2017, 03:45 PM.

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