54 replies to this topic

[Pablo]

My next project:

 

 

I just love the way IRRA® founding fathers wrote clear, concise rules. It makes my job so easy. Now, where did I put those doggone non-hypoid FK motor brackets?    and those R-Geo flag thingamabobs? 

 

(Correction 5/29/20 - the body was in a wrong bag - this is not a TrueScale 40.)   

[Pablo]

Thanks to Noose for answering my million questions today.  Parts gathering has begun. The current rules don't show it, but the JK Mini-Brute is legal and the cool guys are using it successfully.

 

- JK Jail Door Motor Bracket

- JK Hawk MB Motor 

- Pro-Track Jail Door Fronts 1/8 x 7/8 x .300 - PTC-514 
- Pro-Track Jail Door Rears 1/8 x .950 x .500 - PTC-N517
- Sonic straight steel 8T 48P pinion

- Parma 28T crown

- R-Geo flag gizmo

- Red Fox flag

 

Wheelbase 3 7/8"

Guide lead 3/4"

Front and rear track 3", front 1/8" Cukras slop

 

 
 

[Don Weaver]

8/28 = 3.5 ratio with 0.950 tires seems a bit much for a Mini Brute.  Just my opinion/guess as I have never owned a M/B.  I'll be quiet now ...

 

Don

[dc-65x]

Yummy, a Russkit Lotus 40 me thinks.  

[slotcarone]

8/28 = 3.5 ratio with 0.950 tires seems a bit much for a Mini Brute.  Just my opinion/guess as I have never owned a M/B.  I'll be quiet now ...

 

Don

If you are racing on a commercial track that gearing should be fine.

[Ramcatlarry]

Got a LONG straight for that gear?   We are running 7/33 with those tires on a slower motor - and not burning them up.

[slotcarone]

Not familiar with the Pro Trac part numbers but they make hard and soft fronts. Make sure you have the hard ones. The soft ones will not work!

[slotcarone]

Got a LONG straight for that gear?   We are running 7/33 with those tires on a slower motor - and not burning them up.

 

The JK MB motors can take a tall gear and still have plenty of brakes. They get warm but so do other FK motors. I am talking about racing competitively.

[Don Weaver]

We are running 7/33 with those tires on a slower motor - and not burning them up.

7/33 would be 4.71:1 which, to me would seem more in line especially with that tire diameter.  But then, I still haven't bought a M/D motor;  It just seems to be a more reasonable ratio...

 

Don

[Pablo]

The gearing info came from one of the (two) founding fathers of R & C ruleset, based on his personal race experience. I didn't just pull that out of my keester, Bunky 

 

The car owner just pointed out a colossal goof-up on my part - the TS body bag is Sharpie marked "PTEG" (which is wrong in and of itself, it's "PETG") but the body itself is Sharpie marked "Lexan .010" 

 

How in the $%*@ does that happen, I don't know. Obviously a nice big brain fart on my part    Looking at the body, it's obviously Lexan ®. What can I say? Doggone gremlins are running loose in my hobby room while I sleep   

[Pablo]

Don, if you think that ratio may be too tall, you may want to watch my JK Indy motor swap thread for a really sick tall gearing choice. It's a motor that's never been race tested and it's going to get the "Pablo's hand out FK motor gearing theory" no BS - "keep increasing pinion size tooth by tooth until you cook a motor, then back off one tooth"    It's been tested and proven to run cool with good brakes at 15/34 with .730 wheels. I may go even sicker than that.

 

http://slotblog.net/...car-motor-swap/

 

Also, let's keep in mind the rear wheel width on this jaildoor is .500 max. So we aren't looking at a full .810 wide tire patch with Koford Heavy glue, it's a car designed for controlled drift with a toothbrush motor. 

[John Streisguth]

The MB wind is very mild, very low (if any) advance.  Worst case, pop a 30T crown in  if it's a tight track.  But 8/28 was pretty standard when we were running the JD cars.  With a 7T pinion, you would probably be disappointed with the top speed.

[Pablo]

I bought two JK jaildoor motor brackets, one for this car and another for the Lola. This one required a lot of work to make right. The other is fine. After lots of tweaking, checking, filing, hogging out holes, it's finally good to go with jig motor in place.

 

Tube length is 1.600" and jig wheels are 13/16 which will give 1/16" clearance with .940" wheels

 

 

Tube tacked in place, a Q/A check for alignment, and a sliver of 15 thou brass under the front edge of the jig motor ensures when Noose passes a 1/16 tool under the entire car it won't snag

 

[slotcarone]

Looks good so far.  Mr. Noose won't be teching this one as there are no Retro East JD races anymore. We only race them at Doms and Race Place in Jersey.

[Pablo]

Jig setup:

 

- WB 3 7/8", GL 3/4"

 

- Front axle tube 1.985". Using the Pro-Track front wheels it meets the rules - 3" max, allows for 1/8 Cukras Slop. 

 

- Front jig wheels are 3/4" which give 1/16" clearance with .875 OD wheels

 

[Pablo]

Thanks Mike, I hope whoever techs this car is happy with it. Noose sets the standard for retro car inspections in my book. If it is to Noose Standards, it's going to be a great car in my opinion, no matter who techs it 

[Pablo]

Rules allow a wire bracket brace and I chose .047. With a MB motor, it won't hit the wall as hard as a Mura 

 

 

My jaildoor chassis building tip of the day is, one piece (rail) at a time, tack only, finalize joints later. Everything is bent and cut to fit precisely. Nothing is force fit and no shortcuts.

 

I've built enough Cukras and Steube replicas to know. I'm just copying the masters, but I have lots more time on my hands than they did 

 

[Pablo]

Progress report - single rail inside the bracket, followed by a 1/16" space and a double rail set. Everything is getting stronger as the "tack" joints turn into full hot flowing solder joints

 

 

"Nobody is breaking out of this joint alive" 

[slotcarone]

Looks great Pablo. I don't have the rules in front of me but make sure they allow more than one rear bracket brace.

[tonyp]

Rules should say 1 piano wire brace in bracket.


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[Pablo]

Thanks Mike. Rules say one wire brace (only). Nothing in the rules says no additional rod braces. My lower one is wire and the upper is brass 

[tonyp]

That’s legal.

[Pablo]

 

 

I re-read the rules every time I fire up the Hakko    They are very clear and concise, I love them 

[tonyp]

Thank you.


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[Pablo]

 

I have reached the limit of rails allowed and I think it's plenty.  All solder joints finalized, jig motor and jig wheels come off. Everything given a good scrubbing and iron unplugged