75 replies to this topic

[MSwiss]

Like that, except IIRC, his are alongside the rails which would be weaker.

FWIW, he seldom hits anything.

[MSwiss]

... I was asking about if his chassis had these.

Again, IIRC, yes.

I'm not totally sure because I might be confusing the JK with the Warmack car he let
Howie practice with for about five hours a few Fridays ago.

[MSwiss]

Marty,

BTW, thanks for posting that pic.

I had a call earlier from one of the SoCal A Main racers asking about Sano Dave's chassis.

He had a hard time picturing how .047" wire in a 1/8" square tube could have up movement but no side movement.

Your pic illustrates it perfectly.

[Hworth08]

Wonder if a setup similiar to what JK used on their Scorpion 3 or 4 (can't remember which) would be legal?

JK had some problems with that frame, as the stops wouldn't stay tight but the racers started soldering various stops on the bite bar that solved that small problem.

According to people that used that Scorpion frame, the system did work and they could feel a fair amount of difference in side bite depending on the amount of side play.

[MSwiss]

I remember that because Koford use to make those collars for JK. I think one reason they came loose was racer resistance to putting a little flat on the bite bar for the set-screw to dig into.

Anyway, IMHO, we don't need adjustability.

I don't allow glue boarding on my tracks so racers are always looking for more bite.

On the Flat track, even using the bitiest tires out there, I've yet to drive a Retro car that has too much bite. At 115+ grams, these cars never get tippy. If we ever do come up with too much, we can always tune it out with harder or narrower tires.

[Mark Johnson]

Mike, what did the finished product come out ready to race weight-wise???

[MSwiss]

I haven't had a chance to fimish it up, yet. Along with M/O business, I've been busy this week working on pit spaces for the Sano.

The bare chassis with the fronts installed comes out to 72.9 grams.

[Noose]

That weight should yield a car in the 118 gram range. Maybe a tad more. Should be great on the flat track.

[MSwiss]

On the first torsion style chassis I built, I weighed it down to about 124 grams.

[Jobiwan]

Just wanted to say thanks to Mike Swiss for the thread on building the JK Spec chassis. I just finished the one that I got from Mike and I can't wait to try it out.

[MSwiss]

Ray Price picked up one of these a few weeks back and I decided to try it
last night.
I had to take a short break from a current project to show it to you.
It's Dremel EZ545 diamond tile cutting disc. I've used ones before but the
quality, grit and large 1.5" diameter makes it the easily the best cutting device I've
ever come across.

It's .022 thickness combined with ultra-clean cutting produces such a
thin, clean, & square kerf, you won't believe it.

It will change your life.

I'm not sure what he paid for it but it was well worth it.

[MSwiss]

I'll add to my post about the Dremel diamond wheel that it's superior
performance is with cutting piano wire.
The Dremel big diameter fiberglass wheel is better for cutting brass strip.

[Tex]

OK, I'm finally getting around to "looking" at the JK pan that Allen Reeder gave me at DA Sano II(ONLY a month later... a record for me!). Does the out of the bag chassis yield a rear clearance of .050" and a front clearance of .015"(directly under the front axle)? The reason I ask is that a downward/forward "rake" of the chassis is created by the different clearances(rear vs. front) AND there is chassis/pan material extending forward of the front axle AND IF the clearance under the front axle is .015" then the material extending forward from the front axle has LESS THAN .015" clearance, right? In all my retro chassis' I've built, I have made a slight bend, directly under the front axle, to any material extending forward so that ALL of it maintains the .015" clearance. Does anyone else do this? Or am I overworking this issue and handicapping myself needlessly by doing what I do?

[Noose]

You will get the .050 rear for sure but for the .015 all the way to the front you will need to do one of 2 things. Either open the front axle hole a bit (downward) or use it as is and get the JK "IRRA" Fronts (Swissablo has them). The JK IRRA frots are slightly larger than .750 so you can get the clearance.

[Chris Barnes]

Is this legal for IRRA rules? Is this considered bracing of the bracket? What about the two pieces of brass on the insides of the bracket?

We'll also be adding a weight to the front of the bracket. It will fit under the motor as I am using a standard, non-hypoid bracket. While it won't be as effective as a finned aluminum model, it will also act a low profile heat-sink.

Use a piece of 1" wide X .032" thick brass. Set your calipers to .920" wide and use the outer tangs to scribe a line on the brass.



Trim it with your nibbler or Dremel and smooth out the cut edge. Center and install it with the .920" dimension inside the rails as not to interfere with the flex.

Don't be afraid to also try it turned 90 degrees and soldered to the rails. That's part of the fun with these scratchbuilt cars; the infinite ways you can fine tune them and the resulting handling differences.

Use the 100 watter, and quickly, as not to effect all the solder joints nearby. Easy on the flux, making sure none of the solder interferes with your motor installation.

[Noose]

Both are fine.

[Chris Barnes]

Thanks,

Chris

Both are fine.

[Tex]

OK, I finally got around to building up the JK spec pan that Alan Reeder gave me. I didn't have fun. While the pan itself wasn't perfectly flat when I got it, I fiddled with it a while and got it pretty flat before soldering anything to it. However, once I soldered the main rails in(.063) and the piano wire reinforcement braces up front, the pan warped pretty good. I figure this is due to the different expansion/contraction rates of brass vs. steel when heating up and cooling down. Has anyone else experienced this? I notice that Mike had his pan clamped down since he wasn't using a proper building jig; I wonder if clamping it down prevented or greatly reduced any such warping(?).

[Chris Barnes]

When I built mine, I used a torch for final solder "flowing". The heat is pretty much distributed across the brass and wire. I did not notice any warping after it cooled. Also, I ensured that there was no bind in the wire slots. I used 0.078" and opened the slots to be clean but not too big. Wires would fall through, but not a lot of slop in the slots.

[Don Weaver]

Tex,

I've had this problem occasionly, especially when I'm soldering steel wire to thin (.032 and smaller brass). I've found that if I start in the middle and then flow solder first towards one end of the steel piece and then towards the other end the brass brass doesn't warp up. I think that what happens is if you start at one end and then move towards the other end the first part of the solder joint cools and as the rest cools down you get a bi-metal effect.

Don Weaver

[Richie]

I was able tonight to run my "spec car" on its maiden voyage. This is the first retro ride i've built, and I am extremely impressed in the way it handled!!! on our king track (147' tight, flatter king) most flexi's 4" with a falcon run in the higher 4's... lap record is a 4.72 with a .010" thick GT-1 body. I'm pretty sure we could get that in the 4.6's now though.. Anyways, this car I wasn't expecting much... didn't have it geared quite perfect, (8/28) needed more gear, ran several really low 4.8's. Needless to say I was extremely happy right out of the gate... Time now to work on dialing it in but so far just a huge grin ear to ear!!! I want to thank Mike Swiss for showing everyone the torsion car, as that works great!!! 4.6's here we come next week!!

-Richie

[Mopower71]

OK, I finally got around to building up the JK spec pan that Alan Reeder gave me. I didn't have fun. While the pan itself wasn't perfectly flat when I got it, I fiddled with it a while and got it pretty flat before soldering anything to it.

Is it shipping that is distorting the pan, or is it when the front axle uprights, and pin tube holders are bent into the pan. It's a nice looking chassis, but mine was a bit distorted between the front axle uprights, and took some work to get it to lay as flat as possible. Also, the main rail wire was arched between the end and the 90deg, and just not bent at 90deg

[MSwiss]

They are stamped. Flatness seems to vary a bit from pc. to pc.
I can't say if it's the initial stamping or the secondary bending
of the front wheel and body mount uprights.
You could chalk it up to being Made in China but the Made in China bracket
is absolutely superb.
The good news is the JK, along with being quite a bit cheaper, is the only
currently available nose pc. that comes with those uprights prebent.

The JK main rail(which I'm pretty sure is Made in the USA, leaves a bit to
be desired. I don't even bother to stock them.
Quite a few guys have wire benders designed to make that main rail
and bend their own.
Those who need the main rail, I supply them with a nicer bent one for the same price.

[Shooter7mustang]

Hey, Mike, do you have video of that build?

[Noose]

There was no video but you can get a print out of the how-to article HERE.