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Old 03-29-2010, 01:23 PM   #271
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Originally Posted by John Stranahan View Post

Sweep Racing EXP 36R
I offer these fixes in order to improve the breed of a tire with good grip and performance. It is not a criticism. You may never experience this on a slower track. This is the second total blowup, but the first tire had a cut and I had glued it myself.
yes John

this is why I contact you in first place, IMO you are track is the only one in US does open modified TC racing. and your the right pilot to test em under extreme condition.

if all our testing were done with a machine with 21.5t/4 cells, we will never find this out.

and I also remember asked you to post the results either good or bad, on -line instead of emailing me first. so we can all see and gather ideas. Toyota learned that in hard way.

this thread has been viewd and discussed by engineers at Sweep Racing HQ and us in the State, we re considering many solution to prevent this kind of incedent.

thanks again John keep up the good work.

Regards

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Old 03-29-2010, 10:00 PM   #272
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Edited so no one gets confused on the math of measuring the correct gears

Last edited by TXstreetracer; 03-30-2010 at 05:48 AM.
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Old 03-29-2010, 10:57 PM   #273
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Sweep Racing Usa-Thanks for the post. Good luck!


TX street racer- Let me simplify to only one formula. Use the calculator and trial and error to see what your car ratio is. For a 35 pinion and 86 spur

take 86 divide by 35 then always mulitipy by the cars internal ratio 1.83

I get 4.4. Most guys just do it this way.

Note I messed up the math which may have caused you a problem. The correction is below, but this simple way is easy to remember.
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Old 03-29-2010, 11:03 PM   #274
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TX Street racer, Note I messed up the math and that may be why you had trouble. This is the corrected version with Paralectic correction on car ratio as well. Looks like you need pinions about 23 teeth. It would also be helpful for you to delete the wrong math in your quote.


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We were one short to make an electric heat at the Soutwest Series race. I showed on Saturday.

Put a 3.5 in that puppy and come join us. We race again next Sunday at 12:00 Noon. The lanes are huge.

I had posted overall ratios previously. Sorry if this was misunderstood.

Car ratio = spur/pinion x internal ratio
a 12 pinion gives you 88/12 x 1.83
or 13.42 too low. No speed.

You are lookiing for gears in the 7.0 range.

7.0 = 88/x (1.83)
7.0/1.83=88/x
x = 88 x 1.83/7

or rearanged pinion = spur/car ratio
x=23
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Old 03-30-2010, 05:42 AM   #275
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Quote:
Originally Posted by John Stranahan View Post
Sweep Racing Usa-Thanks for the post. Good luck!


TX street racer- Let me simplify to only one formula. Use the calculator and trial and error to see what your car ratio is. For a 35 pinion and 86 spur

take 86 divide by 35 then always mulitipy by the cars internal ratio 1.83

I get 4.4. Most guys just do it this way.

Note I messed up the math which may have caused you a problem. The correction is below, but this simple way is easy to remember.
John, THANK YOU so much.....NOW I comprehend the math.....and will order my gears.

I'll edit my other post so no one gets confused
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Old 04-01-2010, 03:42 PM   #276
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Anyone looking for a G+ ?

I have two. Just bought a JRX-s R to play with and can't justify 3 touring cars.
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Old 04-21-2010, 10:29 AM   #277
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Here is a link to a suspension tuning reference that I just completed putting on the Web. It consist of a chapter in a book that I wrote titled RC Electric Car Reference. It is updated to the third edition now. There are some excerpts from my threads. The title of the chapter is "Cornering at the Limit". It is good to have a high speed connection. For the first time in glorious color.

http://www.stranahan-rc.com/corneringatthelimit.html
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Old 04-21-2010, 10:52 AM   #278
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Quote:
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Top work as usual John with plenty of information and practical testing to back it up, bit heavy going but good
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Old 04-26-2010, 12:36 PM   #279
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Conrad- Thanks. One thing is assured in that document. The physics is correct. Very often in RC articles and documents it is completely messed up. The reason is that I consulted the full size car books and I have a background in Physics and Chemistry. Here is that link again in case some of you missed it. I did an angle trim on the ends for tire clearance.

Cornering at the limit

Fifth Body Post, Droop

The XXXS continues to perform with little trouble. One thing I miss from the JRXS is that fifth body post that is center back on the hood. I am running Protoforms LTCR body which is a lightweight. It is quite floppy. I had the front dam at 8 mm to keep it from rubbing on brakes even though the front of the chassis is at 6 mm. I was able to lower the front of the body after the mod. I put on this body post by drilling a hole from the front of the car. The hole will notch the frame on the backside. I sanded a rear body post to fit the square recess and then through bolted it. It is in a perfect place on the body. This stiffens the front hood so the wheel arches are not continually flexed. This will prolong the wheel arch life which is usually the cause of discarding the body.

Droop
I have been happily running 2 mm of droop front and back without checking it much. Easiest way to check is measure the ride height. Lift the chassis corner until the wheel is about to lift. Measure the ride height. The difference is the droop. I reduced droop to 1.5 in the back. Here is what happened on the track. The car became a little more responsive but slightly loose. It skidded more easily. The worst that happened was on brakes coming into the hairpins. The whole car now shuddered. This was visible on the bottom sides of the car which developed huge ripples. I suspect the rear tires were now leaving the ground and hitting the top of ripples in the asphalt which happen to be located in the braking area. Anyway, I plan to go back to 2 mm where the car was happier.

Bumper
I wanted a light bumper. I actually have the heavy reinforcing top plate to the standard bumper. It is too heavy. I ran just the foam for a while, but it is very soft. here is a light alternative. The CRC 1/10 foam bumper is a very stiff foam and is wider than the stock foam. It is not too tall however keeping it light. It is wider than the stock foam. Give it a try.

Pack overheating
We had one racer plump up a ThunderPower 52C 5200 2S LiPo. This occurs a little higher than 140F. He had recently installed an LRP SPX8. He was so thrilled to be able to run 6 minutes that he continued till about 8 or 9 minutes. This overheated the pack and the motor. There still are limits to be observed with the new speed control. Shows you how these ratings are not true world. The pack should withstand a 260 amp discharge in 72 seconds at a 50 C rating.
Attached Thumbnails
LOSI XXX-S, Tips and Tricks, Open Mod, etc-fifth-body-post-001.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-fifth-body-post-002.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-fifth-body-post-003.jpg  
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Last edited by John Stranahan; 05-03-2010 at 06:32 PM.
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Old 04-26-2010, 01:05 PM   #280
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Just been reading that article - cornering at the limit

very well explained an fairly easy too read
some great info there once again John

several pieces of info there that has helped assure me of some the ideas I hav been thinking of trying etc

nice body post mod too
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Old 04-29-2010, 12:03 PM   #281
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John, I've posted a link to your website on the "stock" XXXS thread....AGAIN. Can't tell you how invaluable I think this is. In this day and age when we have cars being sold that are largely pre-built AND some without a manual, the concept of a 10+ year old design being able to benefit from your direct experience is fantastic. I'll be putting some of your guidance to test when our club races again next week.
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Old 05-03-2010, 06:29 PM   #282
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Paraletic, Evoracer-Thanks.

5 months later-
I broke my first belt and outdrive this Sunday. The belt is about 5 months old. Telling signs were the belt had stretched to where the adjustment was almost against the stop. I have been running the blue belt and was very happy with it for mod. I installed the black belt now.

I rebuilt the rear diff for the first time as well. It was a bit rough but still usable. Easy to do if you are changing the belt. I had a Los 2933 Gen II diff hardware screw that has a big coil spring in it. Did not seem to fit as there was no longer room for a dogbone. I used the standard screw with beleville washers.

I put a little more droop in the rear by unscrewing the shock ends a turn or two. The shocks were restricting the droop. I wanted 6 mm ride height and 2 mm droop. The shocks are still smooth and have plenty of oil.
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Old 05-04-2010, 05:13 AM   #283
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That would almost have too be a record for the life of a diff in a mod touring car

are you running the losi threaded shocks John?
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Old 05-04-2010, 09:52 AM   #284
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The front shocks are threaded. The shocks that I examined are the rear shock which are original RTR. Stormer was out of stock on rear shock bodies. They show some in stock now. I ordered some new rear threaded bodies yesterday. We will see if they actualy show.

There is also very low wear on the front outdrives. I have replaced the rears for wear twice now because the dogbone eats a divot where it contacts the outdrive. This impedes suspension movment some.
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Old 05-04-2010, 07:30 PM   #285
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How big a 48 pitch gear can you fit

This was a curiosity for me. Chances are I will never fit such a gear. I did manage to fit my biggest 48 pitch 47 tooh pinion with a 90 tooth spur. That's a final drive of 3.50 (maybe for the inevitable 30 turn brushless, or for your top speed run with the 3.5 motor).

Here is what I would do to repeat the install. First mount the desired gear with one screw on the motor plate. You want to achieve two things. Gear clearance and a relatively low motor. I found it easier to insert the motor with gear attached and then put in the spur and belt adjuster unit. Get things close to right and mark the motor and motor plate so you can reassemble them in the same orientation.

I made a pointed 3 mm screw to locate the hole to be drilled. (This is a common machining aid, a transfer screw, that you can buy). Take the enbell off the motor attach the Losi motor mount plate in the desired orientation and run your pointy screw into a suitable hole in the motor from the inside of the endbell. One of the higher holes is more suitable with huge gears. The screw will mark the Losi mounting plate. Now center punch that mark, then drill .120 or slightly bigger. .125 is the is the drill in your Dremel kit. Mark the inside of the very front of the motor hole with red Marks A lot or whiteout. Put in the motor and turn the gear. Dremel a little plastic out for gear clearance. The small drum sander worked well. Done.

You will note a little notch I dremelled in the upper spur gear opening. This gives me clearance to use a standard L-shaped Allen wrench to adjust the gear side to side for a perfect gear mesh. Note the motor clamp reinforces this area so it is not too weak.

You can have more than one hole on this plate. It is not too important which two holes you select in the motor. No cost.

Stock Motor Racing
There may be some 17.5 TC racing developing in Houston. We meet Thursday. Races Tuesday Evening. I'll see if a sufficient number show.
I don't plan to do anything to the car except change motor and tires at this point.
Attached Thumbnails
LOSI XXX-S, Tips and Tricks, Open Mod, etc-losi-xxx-s-47-tooth-pinion-001.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-losi-xxx-s-47-tooth-pinion-002.jpg   LOSI XXX-S, Tips and Tricks, Open Mod, etc-losi-xxx-s-47-tooth-pinion-003.jpg  
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Last edited by John Stranahan; 05-04-2010 at 08:42 PM.
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