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'Switchup' race tuning, vol 1 - F1 on a speedway


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#1 JimF

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Posted 04 June 2018 - 03:22 PM

Setting up for our switchup race @ Motown Vol 1:

 

Formula 1 on a speedway track…..or what did I learn in school today?

 

This will be a lot more detailed than most of my setup articles because we have some new guys that have not raced a switchup race yet. Also, I have never really done a thorough explanation of some of the factors in play when we change track styles. Due to the length of this and future articles on this, I’ll divide each article by car class. Sorry about the length of this one, the next two won’t be a long.

 

So….I got in an overnighter at Motown Saturday night and this was a very thorough test session as opposed to practice. What I mean by that is that when I test, I may only do a few laps with each component or change. I wasn’t looking for an ultimate setup for any particular class (although I think I did find one) Rather, I was testing different general concepts in order to determine future directions.

 

Formula-1 on the Hillclimb. I was testing a new car here but the main focus was intended to be…..sorting out a stack of the various Mini Brute variants that I had in my motor box as well as checking tires, gears and bodies for speedway use. (Our normal usage for our F-1 cars is on flat tracks)

 

 

Here’s a look at the stuff I tested……….

  • A new F-1 chassis that looks similar but is notably lighter than previous ones that look similar.
  • Weighting variations on this new chassis (assuming that it even worked)
  • A wild assortment of the various motors we’ve used in this class for the last 1 ½ years.
  • Several different gear configurations. Sort of testing some ingrained Ideas that I had.
  • A herd of different tires in differing brands and hub sizes.
  • Higher vs. lower downforce bodies. Parma Matra vs. Edge Lotus 49.

 

Conclusions………………..

 

Chassis and weight:

 

This chassis initially came in at 87 gr. all up with body. Right from the jump, this car was stupid fast but “jump” is an applicable term here. This thing was a rocket on the main straights but was very critical off the corners. When I pedaled it just right…..best laps I’ve ever done here. But I was doing a lot of walking. I added the “flat track” center weight assuming that this 13 gr plate (car was now 100 gr all up) would slow me down. Surprisingly, it didn’t….by much. I was now able to get off the turn without feeling like I had to tiptoe. It was visually slower down the straights but was so much easier to drive that there’s no question I’d race it weighted. I had assumed that I’d need to get my car really light in order to compete on this track. Fact is, it was just fine at 100 gr. I don’t think I’m going to be as concerned about light weight now as I might have been in the past.

 

New chassis before setup. Add all running gear and a body = 87 gr.

 

5-20180531_214809.jpg

 

How I finally settled. Center weight in but no additional tuning = 100 gr all up

 

1-20180604_122009.jpg

 

Motors and gearing:

 

We are almost universally using the newest JK Mini Brute in our F-1 cars, but there are other, older motors that we still allow. I had a batch of H&R Lightning 2 and some older S7 MB in my inventory and I decided that it was worthwhile to sort them into keepers and paperweights. The new JKs are a known quantity by now but don’t ignore any of the others that you still may have. The motors were switched one by one into the F-1 chassis and run a maximum of 10-15 laps looking for the top time and the rough 3 lap average. They were all geared at 9-27 initially. I also took note of differences in “feel” (subjective analysis) Occasionally, one of them would feel like it could use a different gear and it was retested with a gearing change.

 

JK MB = One dog but the rest very consistent including the #1 for speed. After that, the JK was #3,4,5 in speed with none more than + .1 slower. Most felt reasonably smooth and easy to drive. I eventually tested a random draw of three of these with a 9-29 and the results were inconclusive. Aside from slightly more brakes, they ran just as well with the 29t as with the 27t. There was no advantage but no drop in speed either.

 

OLD S7 MB = One that was #2 in speed and might have been #1 but was a little more harsh and needed different gearing. Two others were still serviceable at about +.1-.2 on the speedway but fine for flat tracks. The one motor really needed a 29 to soften it a little on exit. The other good ones were fine with the 27.

 

H&R Lightning 2 = When the old square hole S7 Mini Brute dried up, this was an abortive attempt by me to get something that wouldn’t obsolete the old S7 MB. While these motors fit the spec, they missed the target as they were wildly inconsistent. A very few were rockets but most were somewhere between mundane and terrible. There were a couple of discards from these but I’m keeping two that were about .1-.15 off of the best in speed but very easy to drive. I retested one in a stock car on the flat track and it was just as fast as a JK that had tested quite a bit faster in the F-1 on the hillclimb.

 

3-20180604_122606.jpg

 

Tires and Hubs:

 

My tire assortment is pretty standardized but I added a couple of new variations for this test. I usually run an assortment of the following…………

  • JK Natural in small and Big hub (8703PP and 8713PP)
  • JK Premium in small hub (8703PPP*) There are various designations for these.
  • Alpha Piranaha in regular and big full hub. (I use the regular a lot but seldom use the big)
  • For this test, I added some Alpha in regular and big that are not full hubs.

I started the F-1 with the center weight out and JK 8713PP. The car was rocket fast but pretty touchy on exit. I figured too much side bite so I went to JK 8703PP and it got a little better but not much. Then I went to Alpha regular full and then Alpha regular. Each got incrementally better but not enough to make it comfortable. At that point, I just slapped in the center weight and from that point forward, they all worked. With the weight in, (100 gr total) I would have been happy with any of them but did the motor test with the Alpha regular full. BTW.....an Alpha "regular" is the same hub dia as a JK "small" Given the results above, there was no reason to test Alpha Big hubs or the JK Premium plus.

 

I had not purchased a set of non full hub tires in years but I think I’m going to add them back into the mix. They seem to be a little less grippy in side bite than full hubs.

 

Note: The top left is the JK premium plus. It is the same hub as the 8703 but NOT the same rubber.

 

4-20180604_124116.jpg

 

Higher vs. lower downforce bodies:

 

With the advent of the Parma retro bodies, we have all pretty much settled on the Matra MS80 which has a pretty substantial wing. I have also been using some TrueScale and Outisight Lotus 49 occasionally when I thought maybe a bit less rear wing was a good idea. Those bodies are pretty much not available anymore so I have tested the “Edge” Lotus 49 variations. There are a couple versions shown here but none have as much rear spoiler as the Matra. These are available from Buena Park by phone and I’ll consider them legal.

 

I do not consider the "Edge" BRM F-1 legal at this time.

 

There was little to no appreciable difference between the Matra and the Lotus. Fastest laps came with the Matra but the Lotus was fine too. There’s probably no reason to buy the Lotus unless you are just tired of the Matra or tired of all the cars looking the same. I sort of like the Lotus for those reasons although the detailing isn’t as nice.

 

2-20180604_122419.jpg

 

 

 

Next volume will be Can Am on the flat Korkscrew.


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Jim Fowler




#2 boxerdog

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Posted 04 June 2018 - 04:45 PM

I thought I saw evidence of a trespasser on the premises. 


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David Cummerow

#3 old & gray

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Posted 04 June 2018 - 09:28 PM

Thank you for the post Jim the thought process is very informative.

 

The new chassis is interesting can you give details please?


Bob Schlain

#4 JimF

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Posted 04 June 2018 - 10:48 PM

I thought I saw evidence of a trespasser on the premises. 

 

Dang! I thought I'd covered my tracks. Was it the campfire back by the flat track?


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Jim Fowler

#5 JimF

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Posted 04 June 2018 - 11:09 PM

Hey Bob! Sure, no prob.

 

4.065 wheelbase, .925 guide lead. All brass bits at the nose are .050, Center weight is .050. Bracket is an R-Geo .050 "Z-Poid" All wire in center section is .039 with 6 main rails. Pans are 4 X .055.

 

As you can see from the pics, this is a very uncomplicated build although it's a bit of a PITA due to the .039 wire not being real straight sometimes. Although I built this primarily for our next two F-1 races on speedway type tracks, I'm also itching to weight it up and apply it to a flat track.


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Jim Fowler





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