88 replies to this topic

[SpeedyNH]

the rails might be in the same place spacing-wise, but i think that the wider bearing track on the axle would have a greater mechanical advantage in torque on them. 

[Dominator]

Scott you are correct on the rules.  The idea behind the rule set when created was to keep things simple.  Adding extra hinges or hinges that move in multiple directions would complicate building for novice builders.  It's not to say that these designs would be faster but just adds another level of complexity. 

 

Something to remember when building. Designs can look cool but simple works.  And as Andrew said the timer doesn't lie. 

 

Jim you got it exactly.  The wider bracket is IMO more rigid so I have been using those exclusively in Can Am and coupe for almost four years now.  I just started using 3/4" brackets in my latest F1 design.  This design is pretty bullet proof with the bracket and axle tube supports being machined on a single piece of brass.  I have not had one come back bent yet. 

[Phil Smith]

Usually chassis how-do-they-work threads are not very fruitful. Either chassis builders don't want to give up their secrets (understandable) or they truly don't know what makes a chassis tick.

 

This is by far the most informative thread on the subject I've ever read. Thumbs up Dominic!

[Phil Smith]

The clock is not the only gauge by which to judge a chassis. Usually the fastest chassis are not going to be the easiest to drive and the easiest to drive chassis are not going to be the fastest. As a general rule, my experience has been that longer chassis are easier to drive and the same goes for heavier chassis. This is within limits of course. If you have the driving chops you might want to go with a shorter, lighter chassis. If you're a middle of the pack driver like me, a longer, heavier chassis might be a better option.

 

About the only thing I have an opinion on is overall length. Measured as the center of rear axle to center of the guide flag pivot. 4-7/8" is the length I always liked. I've added up many of the wheelbase and guide lead dimensions of various builders on this forum, and often they add up to 4-7/8". So that seems to be a fairly commonly used overall length. And this is not a short chassis. I would call it a medium-long chassis. 4-3/4" is getting short and 4-5/8" and below is no-if-ands-or-buts short. Correct me if I'm wrong.

[Bucky]

To further the discussion and for my own knowledge, how does pan movement impact handling?

What is expected when pans are allowed to move up and down; side to side; front to back? Do all directions of movement have a similar impact? What impact do the various pan attachment methods have ie hinged vs. shaker vs. whatever else?

It appears various pan weights have been effective. Ford-style cars appear to run lighter pans with a lot of movement compared to a Bartos car which appears to have heavier pans and slightly less movement. Both win a lot of races. How does the weight of the pan contribute to handling characteristics?

Are there other considerations regarding setting up the pans, and what impact do they have?

In asking all of this, I do understand there are no definites, but some guidelines would certainly help.

[Danny Zona]

The most important and only determining factor for all this is the computer screen/lap timer after the tires warm up.

When a racer doesn't think the clock is the biggest determining factor they are rarely competitive. IMO.

[Danny Zona]

To further the discussion and for my own knowledge, how does pan movement impact handling?
What is expected when pans are allowed to move up and down; side to side; front to back? Do all directions of movement have a similar impact? What impact do the various pan attachment methods have ie hinged vs. shaker vs. whatever else?
It appears various pan weights have been effective. Ford-style cars appear to run lighter pans with a lot of movement compared to a Bartos car which appears to have heavier pans and slightly less movement. Both win a lot of races. How does the weight of the pan contribute to handling characteristics?
Are there other considerations regarding setting up the pans, and what impact do they have?
In asking all of this, I do understand there are no definites, but some guidelines would certainly help.

We do know up-stops on the Bartos JK kit style chassis slowed them down. I thought it would help but the clock determined otherwise.

[Phil Smith]

When a racer doesn't think the clock is the biggest determining factor they are rarely competitive. IMO.

 

I think you missed my point. When a racer can't drive well enough to keep a fast but hard to drive car in the slot he's rarely competitive. He'll make more laps with an easier to drive car.

[Dominator]

To further the discussion and for my own knowledge, how does pan movement impact handling?

What is expected when pans are allowed to move up and down; side to side; front to back? Do all directions of movement have a similar impact? What impact do the various pan attachment methods have ie hinged vs. shaker vs. whatever else?

It appears various pan weights have been effective. Ford-style cars appear to run lighter pans with a lot of movement compared to a Bartos car which appears to have heavier pans and slightly less movement. Both win a lot of races. How does the weight of the pan contribute to handling characteristics?

Are there other considerations regarding setting up the pans, and what impact do they have?

In asking all of this, I do understand there are no definites, but some guidelines would certainly help.

Up until about January 2019 I usually used .047 for the pan stops.  After talking to a couple other top competitors they convinced me to try using .055.  So I went to Modelville Hobby and did some testing on the Gerding King and the Sovereign.  This allowed me to best test the vertical movement on a higher speed track and a flatter/more drivers style track.  I used a Coupe weighed at 110.5 grams. 

 

On the Gerding laps times were slightly faster with the .055 stop and consistency was the same.   Overall the car was faster coming out of the turn.

 

On the Sovereign lap times were essentially the same but the .047 stop felt more consistent lap to lap. 

 

So which is better?  This get down to more of how one drives.  If your the kind of driver who can drive on the edge and hit the corners hard .055 may be the way to go.  If you want something a little more forgiving .047 might be a better choice.

 

If someone want to hear about body pin placement I can dive into that as well.

[crazyphysicsteacher]

And by the rules, this should not work but it does for a coupe car. 2 047 rails with the tuning fork being 062. The bracket is a 1 inch bracket and makes life way easier. This car has finished 5th over all on the hurricane at The Race Place. The track is fairly flat compared to the others run in the retro east.
And as Dom will tell, I am not the best driver but I can wheel a car.

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[crazyphysicsteacher]

And of course the brass rail beast that comes in at 120 GRAMS but is fast as hell.

I have found that the key to a good design is one that has decent twist flex while has little longitudinal flex at power on. I have tried many designs and have a sub 100 F1 built with a center spine that has great twist and awesome forward bite but there is too much side flex between the front and rear so it is loose off the corner. I have also built a car similar to Rick Moores and have made changes that should make it even more competitive but still need to test.
The bite bars everyone talks about hold two keys, they can limit pan movement but can also be used to add stiffness to the center rails when needed.
I currently have tried lots of stuff and continue to try stuff. I have built copies of cars that have won but I don't like the way they drive. The key to building is being open to new designs and learning from the failures. If you do not understand why it fails, then your only choice is to buy a car and hope it works for you.
Just remember, every decent design provides a location to add lead for tuning.

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[Upfront slot cars]

Bucky, Dom is right on with the pan movement. I really think it depends on the driver. I always build our cars with .025 movement back and forth. And always minimal up and down movement. Like .005 at the most up and down just so she doesnt bind up. I believe you need movement so the chassis doesnt bind up under a load. Generally the more movement you have, the looser the car is. You can easily tighten a car up by taping up the movement in the pans. I build the cats with the movement like that so we can easily tune them to the track as the day goes or even tune them for each lane . If the balance is right and you have the tires that let the car rotate through the center and provide enough forward drive, then you can really dial one in with pan movement. Dont ever listen to people that say this or that isnt that big of a deal. Every piece of the puzzle needs to be used to creat the picture! And if your not doing it, the guy that beat you probably is.

[Ramcatlarry]

We cannot discount the driver ability to make the car perform properly.  Design and fabrication skills are two factors in creating a winning car, but we all try to follow race reports and the able photos from the major races.  Many of us have built good copies of these winning cars and I have also opted to buy a few from the chassis Masters.  Matching your motor with the correct gearing and tires is another major factor that race experience and honest trackside recommendations for last minute tuning.  I think all of my cars are faster when loaned to another driver.

[MSwiss]

I think all of my cars are faster when loaned to another driver.

Larry,
That's probably safe to say. Lol

All kidding aside, I'm still amazed at how fast of marshal's, Bernard and you are, for guys solidly north of 70.

I would say Bernard is consistently faster, but I would put my money on you for the circus / highlight film, marshal job.

[Eddie Fleming]

Andrew touched on one huge thing in chassis setup and racing that being tires.

 

Tire choices are as big a part of chassis performance as anything you do in the construction of the chassis. 

 

Without the proper tires it is not going to work.

[JerseyJohn]

everything matters !!!!!!!!!!!!!

[Upfront slot cars]

Eddie, right on. We find the right tires first and then start tuning the chassis. When you have the right tire you will really be able to tell how each adjustment dials you in or out on the chassis.

[Dominator]

Chris is a heavy hitter at The Race Place, don't let him kid you lol.  What's also great about Chris's designs is he is trying different things all the time and that's what it's all about. 
 
As Andrew said tires can make the difference.  In the Northeast I keep three types in my box.  Thunder mediums usually work everywhere.  JK Wonder (8713PPW) depending on the chassis and track conditions.  Alpha medium Wonder for when the tracks get really stuck.  I usually use Alpha exclusively for Can Am at Premier events and occasionally coupe. 

[SpeedyNH]

Dom, back in Annie, i always built my chassis to go into a corner tentatively and then be able to lay the power on hard and come out with no wag. exactly the opposite of the Wood Man's style, so it was fun to try to make something that would suit both of us! faster in different parts of the track, we'd go back and forth across a lap and both had the exact same lap times on a saturday night! so it worked. 

but then of course, you'd show up and show us the way around. 

more power to ya, bro. thanks for the insight. 

speed 

 

p..s. i couldn't believe your GT-12s, but i think i had the edge in Eurosport.  

SL 

[crazyphysicsteacher]

Thanks Dom. Yeah I am the newbie that has no fear of designs. Just takes too long to build and I lose track.
As Dom said with the tires, I like the alpha wonders the best as they seem to be the most consistent. The jk work well with a smaller hub for F1 and okay in can am. I like the thunders for when I need less bite at the rear to rotate in a corner better.
The fronts, get the lightest you can and make sure you cut then round. Jk tires are known for being a bit square.
While tires are really important, guide depth is really important, build your cars so that you have enough range to adjust for tracks. I have one car that great but the place rebraided and now I don't have enough room to adjust the guide.

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[crazyphysicsteacher]

And Dom, that was the only car that had a shot of beating Jerry for awhile. I almost did it twice.

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[Eddie Fleming]

Chris if you like that chassis remove the guide tongue and clean everything up. Put a .032 (or whatever it takes) shim between the chassis and the tongue and solder the tongue back with the same guide lead it had. I had a chassis with the same problem and that worked great. 

[Shruska55]

One thing I'm getting from all the posts on this thread is that the driver matters as to design and build.

 

After 50 years, I'm still grooving my style. Long memories of racing at 15 do not work as well with 65 year old hands and corrected eyes. LOL So, my original chassis questions were how to build for my own racing needs. At least in the beginning. If I become proficient as a builder, read winning races, then I'll build for my club members if they want me to.

 

Dom talked about the pan movement and experimentation with the actual gauge of the pan stops. It's amazing to think that 0.006" matters!  I also liked Andrew's point about making the chassis as loose as reasonable because one can always tighten, but it's hard to loosen. The rest of the comments are gravy on my mash.

 

Keep those cards and letters coming. I'm leaning a bunch!

 

Thanks for sharing!

ScottH

[crazyphysicsteacher]

Chris if you like that chassis remove the guide tongue and clean everything up and put a .032 (or whatever it takes) shim between the chassis and the tongue and solder the tongue back with the same guide lead it had. I had a chassis with the same problem and that worked great. 

I would, but I have a 062 brass guide on it now I made. So changing it is not easy to do without having the rest of the front wires move. It is no problem, a rebuild of a different car made it even better at that track.

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[crazyphysicsteacher]

Scott, buy a jk kit, better rear bracket and build it as a simple car with a set number of rails. Make sure to use a threaded front Axle as they allow you to easily change fronts and test those. In the begining, don't worry about bearings as good bushings work at the start. Then just make changes to the design. See what works and build from there.

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