49 replies to this topic

[JimF]

Tex:

 

I like that tip a lot, thanks. After reading it, I went and checked and can see no lifting or twisting on the test block but I do see your point. To be clear, with 1/16" fork rails, you are suggesting that I solder a 3/32" round tube into a 1/8" square tube, then drill and tap as before? I wonder if the fit of the 1/16' wire is notably looser in a square tube as opposed to a round one? I've never really noticed one way or the other

 

Couple more things.................

 

My loosening issue is possibly traceable to the fact that I've already stripped the socket on one of those tiny #0 set screws. Probably due to groping through the cutout on the body and not getting the driver in straight. Those little bitty screws are delicate as heck and I think you have to be careful with the wrench.

 

I want to make a sliding block for this too, but not sure that I want to do that now because of some disassembly that I'd have to do to put it on. Still....if I don't have anything else to do Friday night...............

[Greg VanPeenen]

Tex:

 

I like that tip a lot, thanks. After reading it, I went and checked and can see no lifting or twisting on the test block but I do see your point. To be clear, with 1/16" fork rails, you are suggesting that I solder a 3/32" round tube into a 1/8" square tube, then drill and tap as before? I wonder if the fit of the 1/16' wire is notably looser in a square tube as opposed to a round one? I've never really noticed one way or the other

 

Couple more things.................

 

My loosening issue is possibly traceable to the fact that I've already stripped the socket on one of those tiny #0 set screws. Probably due to groping through the cutout on the body and not getting the driver in straight. Those little bitty screws are delicate as heck and I think you have to be careful with the wrench.

 

I want to make a sliding block for this too, but not sure that I want to do that now because of some disassembly that I'd have to do to put it on. Still....if I don't have anything else to do Friday night...............

Jim,

 

The Square tube has a bit more wiggle room then the round tube. That is why I also use 2 MM square tube and .039 wire for my hinges. If you want tighter hinges you can use .041 wire.

 

I built some chassis for high speed tracks with the fork wires soldered in the Square tubes. I have now gone to Split rail main rail design and now run the fork wires floating again. 

 

Great testing as usual. Looking forward to more. 

 

Regards,

Greg VanPeenen. 

[Greg VanPeenen]

Greg--

What was your conclusion?  Just curios about the tunability and your thoughts!!

Tim,

 

My results were the same but more dramatic then Jim's. But my testing is done on a 155 foot long Hill Climb. So my results could have been a bit different.

 

If i were building a very light weight chassis for a really fast King. I would try building a chassis almost like the one I sent to Duran a few years back. That chassis won several races. I would try to get the chassis a bit lighter so the finished car would be around 90 grams. I would run split main rails and floating tuning fork at the front. I would also make the chassis a bit shorter the the one I send Duran with a bit shorter guide lead.

 

Regards,

Greg VanPeenen.   

[JimF]

Greg:

 

Thanks for contributing, that's all great input. After this first spin, I immediately started thinking about somewhat shorter (currently 4") but not necessarily lighter b/c our tracks are just too flat for that. I do build a fair number of cars @ 3 7/8". I also noodled about 2X .047 main rails spaced. I would not be surprised if the next set of tests (165' tucked engleman) might show a greater difference as yours did. The next test will be on a track with historically good bite while this last was on a track with historically the opposite.

[Greg VanPeenen]

Jim,

 

Looking forward to your next test session. 

 

 

 

GVP

[CDavis7]

That was my question/concern. If the flats arent perfectly flat and plum then tightening the set screws will introduce preload into the tuning fork.

Im not knocking the idea. I like it. A lot.

But my building limitations wouldnt allow me to create a tuneable tuning fork without running into my aforementioned concerns

Im eagerly curious to see what your testing reveals.

[crazyphysicsteacher]

​Jim, I second the 2x047 split rails. I run the same setup with 062 forks and a shorter guide lead out here on the east coast. My latest is a coupe car but i am still learning to drive using the front wheels. But,i digress. The 047 rails work really well, i just end up soldering the inner rail to the forks. I may be trying your very inner rail as a change to my setup.

[JimF]

Chris: Thanks for that input. When I get my next test session in (maybe toady) I'll have a pretty good idea of the viability/usefulness of the concept. Right now, it seems worth pursuing. If it continues that way, I'm planning to do more variations. I'm thinking different wheelbases, split rails, and maybe a So-Cally style torsion car as well.

[JimF]

OK....I did get in a test session last Sunday and although it was a good test, I wasn't abl to wring it out in the way I wanted to. First, I forgot the little .028 allen wrench on my workbench at home so I couldn't tighten and loosen at will. Second, the little brass screw block separated from the forward tubes. I attribute this to making the block very tidy and small (small solder surface)

 

So......I tested it unlocked all through the session. The result was that in original configuration, it was as fast on the Motown Hillclimb as the new purpose built 4 rail car I showed along with it. It also turned out to be be my best car on the flat Korkscrew with the addition of some weight on the pans. So, a successful test but not what I had wanted to do.

 

So, when I got home, I did some work on it...........

 

• New forward screw block was made over twice as long as before and this time silver solder was used.
• Sliding block was made to act as an adjustable flex block. Many chassis of this design including most of mine, use a small bit of wire soldered in at the crux of the forks. This will do the same thing but  allow experimental adjustment.

Back to the track next weekend.

 

 

 

 

[boxerdog]

Hey, shine that thing up a bit!!!

[Tim Neja]

My immediate reaction is you'll be happier with the sliding block--and get more consistent tuning than with the fork "lock down" screws in the front!! It should be interesting once you've gotten to test them both! Always fun to see your ideas and tuning/testing skills jim!! Gotta LOVE it!!

[JimF]

Thanks Tim:

 

I have no idea (as usual) how this'll shake out. I plan to start with the front lock loose and the slider loose, then progressively tighten the slider. Then I'll reverse and lock the front and loosen the slider, then progressively tighten the slider. If time permits, I'll do both the Hillclimb and the Korkscrew at Motown. A nice thing about these two tracks is that you can see the cars behavior in a couple of key turns rather than just relying on the clock which can be deceptive.

[Greg VanPeenen]

Jim,

 

Testing that I did determined that the chassis worked more consistently with the tuning fork wires tied together. Further testing found that the location at the very rear just before the fork wires kick out at the rear of the chassis was the best location for them to be tied together. 

 

I'am looking forward to see what conclusions you come up with as a result of your next test session. 

 

Regards,

Greg VanPeenen.  

[JimF]

Got in the next session and was much more productive than the last. With the help of another tester and a kibitzer or two we reached some fairly consistent conclusions. The guidelines for this test were not to change weight, gears or tires at first and concentrate primarily on mechanical features of the chassis and their effects. The tucked Engleman "Hillclimb" at Motown Raceway in Modesto Ca. was the primary venue. Some fine adjustments were tried at the very end and also some testing was done on the flat Korkscrew. For the flat track I made wholesale changes to the running gear and setup so that doesn't bear any comparison to the main tests.

 

Starting point: Slider block loose, forks loose. This ran pretty well but exhibited some wheel hop off the corner (sometimes)

• Tightened the slider at the rearmost position: This cured the wheelhop and was closest to the configuration that I started with. This was very good for my tastes.
• Moved the slider forward about 1/2" and tightened down = maybe a tad looser but no appreciable difference.
• Moved slider another 1/2" = wheel hop was back but very mild. (just a rear tire 'chirp' off the corner when driven hard) car was looser and not stable out of the bank.
• Loose slider tight forks: This combo didn't seem to have much effect.
• Slider tight at rearmost position, tight forks. = This combo was a little more forgiving than with loose forks. Car was not as planted but not objectionably loose.
• Moving slider forward with tight forks = not much difference.
• Tightening one fork but not the other = This was a surprise. The other tester who is a local expert and who drives the difficult black lane better than anyone I know, was mentioning that he was having trouble in the tight left hander going toward the leadon. Tightening the forks helped a lot but then the car was bit loose in the wider turns. So, we tightened the right side fork only and it helped that really tough turn while keeping the car planted better in the other turns.
• At the very end, we also tried a set of narrowed tires and that seemed like a good direction although it was probably the wrong model of tire.
• In the brief flat track test, I found that the car was lifting in the uphill donut in the loose fork, tight slider configuration.
• By tightening the forks, the car stayed planted much better and dropped two tenths with no other changes.
• This gave me a better starting point for other tuning measures.

 

Conclusions to date (uhhh....I think)

• Slider: Confirmed the advantage of a flex block at the crux of the forks. However, it was always better tight and at the crux and was never better loose or forward. I doubt that I'd ever change the slider from rear/tight
• The slider seems unnecessary when a simple wire bit soldered in as a flex block would do the job just as well.
• Adjustable forks: On this day, this feature proved very useful and provided the ability to adapt to the different track conditions. (Hillclimb was a touch loose, flat track was pretty tight)
• Surprisingly, the tactic of tightening one fork enabled us to adapt the car for a specific turn.

 

At least.................I think...................

[A. J. Hoyt]

Jim,

 

They make set screws that have socket and flat tips. Obviously, one could make the tips flat. I am looking at the original picture with the fork rails having flats where they receive the set screw ... with really clear inferences to keeping that end from twisting.

 

From your report, it seems that tightening one rail helped with the tight lead-on turn. I've noticed that a lot of ground (--> time) can be made up when you can drive the lead-on hard on every lane (especially the tighter ones) as you are faster the whole length of the straight (3 mph difference is a walking pace, a step and a half for 1 second long straight) and improves your lap-after-lap consistency.

 

This fork rail differential (different diameters left to right or locked down state) may be a big tuning advantage for oval track cars!

 

I won't get too excited yet but we might have stumbled onto something here! Just pop the lane sticker over the hole ("Illegal body openings! Illegal body openings!") and you can adjust it between heats with the tire wrench!

 

Also, if you put the fork rail on top of the square tubing (batpan hinge outside of the motor bracket), you would be slightly "out-of-plane" so it would work as a small "triangulation" for noticeable increased longitudinal stiffness. Also, you may be able to use a smaller diameter rail due to better lateral leverage due to the increased distance from front fork rail axis to rear fork rail mounting axis.

 

Lastly, it may offer a set screw anchoring point on the rear for each side for even more combinations of tuning stiffness.

 

There, I got it out of my system ... for now.

 

KIITS,

 

AJ

[Greg VanPeenen]

AJ,

 

You are not a believer you in the KISS principal are you. 

 

Most slot car racers are not F-1 , Nascar ,or Indy Car Engineers. Or any kind of Engineer for that matter. Also complex systems are far more prone to failure then simple ones.

 

A simple block on top of the front fork tubes with a set screw on both sides and a set of simple instructions ( tighten this set screw and this happens, tighten the other set screw and this happens, tighten both and this happens. should be doable. Also very very little weight would be added to the chassis using just that system.

 

More then that and you are asking for trouble in my opinion. MAYBE  for a pure R&D chassis for an very astute builder.

 

Regards,

 

GVP.

[A. J. Hoyt]

Greg,

 

That's fair. Most engineers just want to understand the underlying principles and I am likely guilty, as you are implying, of overthinking it.

 

The tuning fork cars work and I think you were one of, if not, the first example I have ever seen of this innovation and I deeply respect your opinion. I don't pretend to know what makes it work so please forgive my rambling in trying to figure it out in front of our unique audience that may be inspired by some of the thinking I expressed. I think this is, perhaps, part of why Jim is doing what he does, too, to "get to the bottom" of why and when the tuning fork works. No one may ever discover how.

 

I am presently following your suggestion and going back to some of my simpler, older proven chassis lately to try to get a handle on a very quirky track we have to race on here in CO. I can only envy and wish for the opportunities to run on the variety of established tracks that Jim has to work with in his area.

 

AJ

[JimF]

Jim,

 

They make set screws that have socket and flat tips. Obviously, one could make the tips flat. I am looking at the original picture with the fork rails having flats where they receive the set screw ... with really clear inferences to keeping that end from twisting.

 

From your report, it seems that tightening one rail helped with the tight lead-on turn. I've noticed that a lot of ground (--> time) can be made up when you can drive the lead-on hard on every lane (especially the tighter ones) as you are faster the whole length of the straight (3 mph difference is a walking pace, a step and a half for 1 second long straight) and improves your lap-after-lap consistency.

 

This fork rail differential (different diameters left to right or locked down state) may be a big tuning advantage for oval track cars!

 

I won't get too excited yet but we might have stumbled onto something here! Just pop the lane sticker over the hole ("Illegal body openings! Illegal body openings!") and you can adjust it between heats with the tire wrench!

 

Also, if you put the fork rail on top of the square tubing (batpan hinge outside of the motor bracket), you would be slightly "out-of-plane" so it would work as a small "triangulation" for noticeable increased longitudinal stiffness. Also, you may be able to use a smaller diameter rail due to better lateral leverage due to the increased distance from front fork rail axis to rear fork rail mounting axis.

 

Lastly, it may offer a set screw anchoring point on the rear for each side for even more combinations of tuning stiffness.

 

There, I got it out of my system ... for now.

 

KIITS,

 

AJ

 

AJ:

 

Thanks for the input although you lost me on the part that I highlighted. I like your points and have thought about some of them myself. On the "illegal body opening" I messed with a little bit of silver vinyl tape that I cut and detailed to look like a gas cap but the lane sticker would be easier since you take it off between heats anyway. I think I went too far on the set screw size. The #0 is so small that it's easy to miss the socket or misalign the wrench and also, they are fairly delicate. I think I'll rebuild this with a different tubing setup in front and will drill it for #1 screws.

 

I'm also not sure but what the flats may have not been the best idea. I think it may be possible that the flats could well exacerbate the potential to miss on the tensioning and perhaps twist the system. I may just order some flat point set screws in #1 along with the cup points. I have to order from McMC tomorrow anyway so I may just do that.

 

This last test was a bit of an eye opener in that both myself and the other tester plus a very experienced kibitzer all could feel and even see the effect. The adjustment of the one rail and not the other was particularly gratifying. I was thinking to my self that "this won't matter" or "I won't even feel it" and I was way wrong. I'm probably a better tester than racer these days but the other guys helped to validate what I thought I was feeling. I hadn't even thought about the potential on an oval but you are spot on with that idea. I haven't run an oval in decades but when I did so.....the effect of offset and stagger were notable. I think this idea of different gauge forks could be pretty awesome on an oval.

[Greg VanPeenen]

Jim,

 

I think I will try your set up at the front tubes if you don't mind. Your results by locking one rail at the front were eye opening. I could see as soon as I read it that it would make a serious tuning tool. 

 

Way to go, with your testing. I have tried soldering the front solid and that works on some chassis like the Razzo and in some limited situations. I never took the time to do what you did. Just proves even old dogs can learn new tricks.

 

Regards,

Greg VanPeenen 

[JimF]

Mind? Heck.....you kidding? This was your original design and I might add one of the few designs that is different from the normal straight rail deals that actually does something. I'm going to be working on an improved tube/set screw design this week or next and just working on the front tubes. As you suggested, that's enough.

 

Thanks for your contributions.

[MSwiss]

Jim,

I think it's great you experiment with stuff like this.

 

Use it to tune, prerace, thumbs up.

 

But to change your car, mid-race, takes a bit of a leap of faith, because it's 3-2-1, you got to go.

 

IOW, feeling out/getting used to the change, like you do in testing, is way different.

 

An example, after bending up wing car in the Nat's Warm-up race , at Beuford's track, in Idaho, I noticed with the car parallellogrammed, and the rear tire sticking out from under the body on one side, it was a dream to drive in the tough turns on Beuf's King, the lead-on on Purple & Black.

 

So I added additional pin holes, to induce that cocked body effect, and had them clearly marked, so I could change the body position, when I went to the gutters on other tracks.

 

Anyway, making a major change, mid-race, I found out quickly, wasn't a great idea.

 

I don't remember the exact problem,(it wasn't time) but I dropped the idea, after one attempt.

[Greg VanPeenen]

Mind? Heck.....you kidding? This was your original design and I might add one of the few designs that is different from the normal straight rail deals that actually does something. I'm going to be working on an improved tube/set screw design this week or next and just working on the front tubes. As you suggested, that's enough.

 

Thanks for your contributions.

Jim,

 

Let me know what you com up with on the front limiter set up. I might ask you to make an extra front tube and limiter set up and send it to me so I can Install it in an existing chassis that I know is really fast. I could test it in a proven chassis and share the results with you. I could also send you one of my newest chassis to play with and test.

 

Regards,

Greg VanPeenen    

[JimF]

Jim,

 

Let me know what you com up with on the front limiter set up. I might ask you to make an extra front tube and limiter set up and send it to me so I can Install it in an existing chassis that I know is really fast. I could test it in a proven chassis and share the results with you. I could also send you one of my newest chassis to play with and test.

 

Regards,

Greg VanPeenen    

 

Will do. I'm not even sure yet what I'll do. Mostly just changing to round tubes and finding a way to use a larger set screw. I'll keep you posted.

[JimF]

Mr Swiss:

 

Totally with you. I don't think I'd be looking at multiple changes during a race. I do think this might be used to adapt to a particularly difficult donut throughout a race or adapting to a certain, difficult turn for a particular heat. Probably though, this is a way to adapt a car to conditions of the day or a track that was changing notably throughout the day, then leave it alone.

[JimF]

No big developments here except a new way to do the front screw block. I wanted to use a bigger screw than the #0 that I started with. However, a #1 is larger in O.D. than the hole in a 3/32 tube. So........I filed a notch into the tube assembly so that the larger screw can bear on the fork rod without possibility of binding on the tube. Then, I placed the screw block (.050) on top, secured with silver solder and drilled and tapped.

 

 

Looks to me like the #1 is about as large as I can go.

 

 

This will go into a very new F-1 frame design that I'm cutting parts for now.