John Stranahan

iTrader: (27)

Thanks for the post.

New Battle Axe 2.0 pic

Here is a pic of the New Battle Axe 2.0 that ran at the Snowbirds. It collected a first in 19 turn fourcell Nastruck.

Several notes.
Note there is more left side chassis than before to support a foam padded Nerf wing. Thats nice. It will protect your right side axle.
Note the ballast on this car is at the left rear most point. Thats where I have been putting some lead lately.
There are five body posts.
The side links are now straight forward.
Pod might be offset left with a new right hand hub or maybe not. It does have the short left hub to allow an offset pod. There are a couple of spacers at least on the lleft side axle, though.
This might be a new Calandra Center Shock.
This car has the extended body mount side plates.

Second and Third pic are the Original Battle Axe for Comparison.
John

raj1

So, if I'm going to use a one cell lipo in my 12th, I need a receiver pack. However, it seems, the esc may try to feed some current to the receiver via the BEC. So, will the receiver pack strategy still work?

John Stranahan

iTrader: (27)

There is no problem with two sources of power to the receiver. We do this all the time when we add a big capacitor to the spektrum receivers. Your concern might be will the receiver pack backfeed into the speed control which will be at lower voltage. The answer is, not likely. It will be the same as running the capacitor. The capacitor will not backfeed into the speed control but simply supplies power when the speedcontrol voltage is too low from heavy amp draw. There should be no problem. You will be pleased with the way the one cell LiPo will retain voltage over many discharge cycles. The receiver pack is a pain in the ass until they develop low voltage receivers and servos. The Nitro guys have been using little 2 cell LiPo receiver packs for a while with a voltage reducer although some are slow to change from the NiMH.

SWtour-This is my suggestion to the oval guys on the velodrome that want to slow things down. Go with one cell LiPO eventually.
John

Trips

iTrader: (16)

When you run a receiver pack, you won't get any power to the receiver from the speed control, because you leave the speed control switched off. In fact, I recommend either making a small blocking plate for the speed control switch so it can't be switched on by mistake, or hiding the speed control switch in an out of reach spot. Some speed controls don't like it when you turn them on while a receiver pack is connected. Even if you're not likely to make the mistake, a helpful marshal might hit the switch on a damaged car thinking he's turning it "off"...

John Stranahan

iTrader: (27)

raj1-My apologies for a hasty incomplete answer. David has set me straight. His is the method recommended by a Tekin Rep on a thread here for the RS1 Pro and 1 cell LiPo.

Here is another method recommended by Trailranger over on Hobby talk. If you are using a 2 cell LiPo receiver pack you need a voltage reducer. Novak sells one. It's called a BEC. You can then pull the red wire from the speed control plug and the speed control works as normal off the battery and has its LiPo cutoff intact and can use the switch.
john

John Stranahan

iTrader: (27)

Inertia or Motor limited Acceleration

When you roll on throttle and there is no wheel slip possible then you have Inertia limited acceleration. This means that inertia in the driveline and the chassis are what is limiting acceleration. This also means you are probably running a spec motor and battery for examble 13.5/four cell. Since the battery and motor are specified you are left to tinker with chassis and drivetrain to improve performance. What to do. First make sure the car is no heavier than required. On a 50 ounce car an extra ounce slows you up by 2%. You will notice this the most when accelerating side to side with a car that is lighter than yours. No need to cheat in club racing just set your car to .2 or .3 ounces heavier than required with very short tires onboard of the lightest type that you will use. This is mostly easy to do these days as some ballast is required. Drill your ballast a little lighter.

Rotating inertia-Rotating inertia holds you back by a factor maybe 2 to 3 times more than the inertia of non rotating parts. The reason is the part needs to be accelerated in a straight line like all the rest of the car, but the rotating part also needs to be rotated which uses up extra energy. The faster the part needs to rotate (the pinion) and the larger the parts radius, the more the part slows you down. I have seen it posted that a lighter pinion will go unoticed. Maybe so. But if you take two or three little lightening steps then you will start to see changes on your lap time. In stock truck a light pinion could be "felt" just by watching the truck out of a corner and noting front end lift. It lifted more with a light pinion; you could see the truck accelerate just a little faster. In mod truck a heavy steel pinion was fine. In the former case we are inertia limited (on blue grooved clay). In the latter case we are traction limited because of tire slip.

World GT Car
What can we do here?. We can use a deep dished lightened Aluminum pinion indoors. The black model in the photo is from Robinson Racing. Some guys are using huge pinions (21.5 guys). It makes more difference to the car when you lighten a huge pinion. Outdoors you really need a steel pinion for durability if you want it to last more than one race day. The dished grey model is made in England by RP. This is the lightest steel pinion I have seen. I had to order this one and ship it oveseas. Lefthander-RC.com has some RP stuff now. Since the motor shaft is the fastest rotating part on the car it makes the most difference to lighten things attached to this shaft. Don't drill out the magnet. This won't help you and would not be spec.
On a pan car the second place to look is the rear axle. Note in the second pic that the inside diff flange that is pinned to this CRC axle has three lightening cuts. Sweet. The light weight diff-ring on the table is also installed and seems to fit and work fine. Ceramic diff balls are lighter than steel or carbide. This set of 12 Track Attack ball are from Left-haderRC.com.
The lightweight diff rings are from Track Attack (lefthanderRC.com) or I.R.S.
Note the red Nylock nut from Hyperdrive (Lefthander-RC.com). It is a thin model for some weight savings here. (Don't use a plastic diff nut or the diff setting is forever changing.)
Note the silver Associated diff cone. Nothing special here. I just forgot to order the CRC parts. The associated part is a lightweight cone but is a little oversize in diameter.
Robinson Racing and RP both make a lightweight 64 pitch white nylon spur gears that is narrowed to make it lighter. This black model from Kibrough is 48 pitch (my selection for outdoor use) and holds a full complement of 12 balls with only 69 teeth.

Wheel lug bolts.-I use 5/16 Aluminum screws. I use four per wheel to keep from warping the wheel in the crashes. The screw should be just flush with the end of the threads in the wheel. Excess length is not needed.

Left hand hubs- There are lightweight left hand hubs available from KSG. Mine became untrue with only a month of use. I have returned to the stock left side double clamp hub. Sometimes you just need the extra meat on a part for strength.

Left hand hub screws- These should be long and should be made of steel and should engage most of the aluminum threads in the hub. You have to tighten the crap out of these for good function. Alternately tightening one then the other until it is quite tight. Otherwise you will lose your wheel on the track. This is not peculiar to CRC but a property of the breed. I put on blue loctite the first time I tighten these two screws. This lubricates the screw and lets it tighten better and then sets up and holds it tight. The Loctite does not need to be reapplied every time.

Break-in those diff balls by holding one wheel and running the motor for 30 seconds. Now recheck the diff nut; grab left tire and spur with left hand; the right side tire should be hard to rotate. You are ready for weeks of use with little attention.

Now you have a world class lightweight axle assembly.

This CRC diff seems to have slightly tighter tolerances on the gear. It does not wobble much. I used to put in a thin 1/2 inch shim to take out some gear wobble, but this is not needed here. The shim actually killed the function so I removed it.
Man those are nice looking hubs! Just came in today.
Pics: click one more time after enlarging them for the sharpest view. Note Green rubber sealed bearing from BOCA for the longest wear. Grit entry combined with high load is mostly what kills this bearing.
John

pejota

iTrader: (12)

John

Is it possible to have too much rear down force applied by a wing?

I have the HPI Corvette body on that 200mm Bolink project i've been working on. The other day when i ran it on a very rough basketball court i could throw the car around and maintain some pretty good speed through some tight turns. The rear end wanted to slide a little but would snap right back into place. I figured that if i added the rear wing that the rear end would be stabilized.

Now i seem to have developed a push. I could point the front end where i wanted and dive into the turn. Now i seem to be plodding through the tighter turns. The only thing different between runs was the rear wing and i swapped the front wheels to keep wear even.

Is it possible to have too much wing?

Thanks!!

Still Bill

iTrader: (16)

IMO the Corvette body is not very good in the front end.

Try the Protoform Alfa Sophia body for its great downforce characterics.

Bill

John Stranahan

iTrader: (27)

Thanks for the post-
Yes it is certainly possible to add too much wing. You could get by with a smaller wing with the car as is. Some wings come with sets of trim lines. Some come in sets of two, bigger and smaller downforce. I usually adjust the oversteer/understeer balance, first, with wing size, then I balance by changing the height of the wing off the body. Maybe yours is too high. Bigger and higher gives more rear downforce more rear cornering traction; the balance is shifted to less steering traction.

Generally a road course with pan or touring car can profit from a big wing. In the case of touring car it cannot be higher than the cars roof. A flat asphalt oval car can profit from a big wing. In the existing Roar rules a GT class pan car can have a huge 2 inch chord wing mounted anywhere (on the roof if need be). I don't know off hand the world GT specs on wing. I will look it up.

World GT specs
Max Chord 45 mm
max side dam 20 x 45 mm


A chord is a straight line. Set the ruler flat touching the bottom edge of the wing, touching the top edge. You must be 45 mm or less. That is a small wing. Better for scale appearance.


You can add mechanical steering if you think the wing is of a proper size. Soften the front (if this is even possible). Or you can add a little more stiffness to the rear (T-plate). Maybe a full width shim at the back instead of washers or something similar. I can't really see all the details of the car from the photos.

Dusty concrete may require more efforts to have steering than medium traction asphalt. Maybe a softer tire is in order. Try the CRC World GT spec front tire if it fits. I found it good in the dust.

Great job on that Bolink. I am glad you are testing. I did visit your thread. Funny some oval cars are just now coming out with bottom mounted T-plates!

Still Bill-What is your second best choice. I am not that thrilled with the Sophia although we do have one in stock.

Speaking of Wings
Every time I go into the shop I look at this graphite wing hanging on the wall and look for a place to use it. $24. It is the real thing not a cosmetic treatment. REALLY nice looking. I'll post a pic and more details if I buy it later. It is not too large or high so would not suit my oval car, but maybe mounted high on the GenX10 World GT car (with a new body). It might also be suitable for an under car diffuser on an Impala oval car. It has a generous curve.
John

pejota

iTrader: (12)

Thanks John!

I just wanted to be sure i wasn't imagining things. Track is very dusty asphalt with patches of old tennis court material. Maybe real fine concrete? Not sure. It's just a beat up old basketball court. One of this first passes down my "straight away" and there were some serious dust rooster tails shooting out the back. Had to smile at that.

Should have told you that tires are RC4Less Pinks all the way around. I could go softer on the fronts if i had the springs. Stiffening the rear may be possible, i look into it before i abandon the wing. There is one other trim line on the wing... can't remember the name but it's like a 1mm "lip" at the top of the wing. I could cut that off.

Thanks for the comments on Bolink. The pivot balls at the back made a world of difference. I think i may redesign the t-plate to incorporate your shock design on the 3-link with panhard bar. I might have enough room to mount the 18T shocks the same way you do. I've also looked into mounting the AE style front end. It would make caster and camber MUCH easier to figure out.

John Stranahan

iTrader: (27)

That would be your Gurney Strip that improves the effectiveness of a wing without adding much drag.

I like my latest 3-link setup. That would be a good move.

I have one other 3-link design in mind that uses many more of the stock Gen X10 parts and the tiny shock towers. I have a cheap way to mount the shock tower.

Pics. These chrome plated brass durro collars provide an inexpensive solution to changing from flat graphite to vertical graphite (or titanium in this case). This will knock $100 off the next 3-link project by not requiring the Hyperdrive Aluminum shock tower nor a change in bottom plate and possibly top plate nor pod side plates. Mostly stock CRC Gen X 10 parts will be used. It will easily convert back to stock center pivot side link. Fit of bottom pod plate seam with the chassis will be much improved. The Durro collar replaces the CRC center shock mount in the last photo.
John

Still Bill

iTrader: (16)

Hi John,

I believe that all but one person at NorCal Hobbies is using the Sophia on their Gen-X 10 carpet cars (to keep on the subject) at this point. Second best is what they went away from...Mostly Corvettes.

Bill

John Stranahan

iTrader: (27)

OK-I am resigned to my fate, and will be picking up a Sophia for the World GT car next Wednesday. Now that I know the modest wing rules, I'll pick up the grahite wing as well.
john

Still Bill

iTrader: (16)

About time that I influenced (fated) you amigo!

Let's see that wing...

John Stranahan

iTrader: (27)

Bill-Thanks. Here is a photo of an Alpha Romeo 8C competizione and the Protoform Sophia at the right. This is the closest match I could find. I found very few of the Alfa cars in race colors. I looked at 30 pages of thumbnails. This may be an amalgamated car from several models like the latest touring car bodies from Protoform. If some of you guys know a little more history on this Protoform body it would be nice.

Al Leake (now deceased) was credited with hundreds of SCCA wins in his Alfa race car which he named after his wife Sophia.

Well you see, the only trouble I had with this body was the name. Would not mind so much an Alfa Romeo 8C Competizione. I actually get to do some machine work and hand fitting of suspension components on antique full sized Alfas for a fellow who works on them here in town.

I would like to see the Alfa car or one similar in race colors say at Lemans or Petit Lemans tracks.

3rd pic: Al Leakes Vintage Spyder "Sophia"
John