Wanna see a XX drag car ? (pics)

[jeepinator]

Here is a little something I put together at 2:00 am one morning after being invited to race at a local 1/10 scale drag strip.
I just happened to have this "extended" chassis lying around. I cut 2 normal XX chassis; one as far back as I could and one as far forward as I could. I ended up with a REALLY long chassis and a REALLY short chassis.
Anyway, I got to looking at the long chassis one evenning and said, "hmmm...." :)
This car has RC10 "worlds" (before B2) front and rear arms, RC10 worlds castor blocks and steering blocks, and the rest is Losi crap.
I normally have the HPI 2-speed on there, but I lost my special pinion ! :( :mad:
Anyways, the red cells are the SCR1000's. They are smaller than normals cells and quite a bit lighter. There are 10 of them in there. I usually run a 15 or 16 turn big commm motor (heheh, big suprize to those that have read my previous posts :p ). I tried low turn motors, but the 14-17 turn has the best ET's believe it or not. The steering servo is a tiny 1/12 scale carpet unit. BTW, it is geared 20/87 with a buggy tranny and truck wheels/tires !
I found overgearing to the moon got the best times (and more control at the start). I am planning on getting some of those Pro-Line foam tires for the XXT soon. Those should hook up much better.
On to the pics:

http://www.theshreves.com/pics/drag4.jpg

http://www.theshreves.com/pics/drag1.jpg

You can see more of my crazy creations on my web page (click on the little house icon above)

Cheers

[ 06-17-2001: Message edited by: jeepinator ]

[Nairb]

What a crazy bugger! How fast did she go?

[jeepinator]

40 MPH (in 132 feet (1/10 scale quarter mile)).
That was then. Now it is quite a bit faster. I have 10 lightweight cells instead of 9 heavy cells and I have a better gearing arrangement (and the 2-speed). When I get the foam rear tires I am going to race it again. I'll bet it pulls a 45 MPH or better in the scale 1/4 mile. Maybe even 50. I forget what my ET times were, sorry ...

Here is a comparison picture of the crazy chassis I made.

http://www.theshreves.com/pics/drag6.jpg

A normal buggy XX buggy chassis is at the top of the pic. The extra short chassis is on top of the drag XX chassis.

[ 06-17-2001: Message edited by: jeepinator ]

[WhoKnowsWho]

Looks pretty cool. How well does that electric 2 speed work?

[Aussie_Man]

Does that ever mono or wheel-stand with a higher torque motor? Looks pretty cool.

[illbreakit]

The really short chassis would make a cool one of a kind mini. Gona hafta try that one day, maybe at 3am eh, jeepinator

[ZenLosi]

Jeep, how did you join the halves together?

By the way, nice creation(s)!

-Zen

[gubbs3]

Nice work. If you spin those speed hawgs too much try Pro-Line truck foams. Those things really dig in on pavement!

[XXXER]

I think that thing is sweet! Keep it up dood.

[jeepinator]

Thanks for the kind words, everyone.

posted by WhoKnowsWho:
Looks pretty cool. How well does that electric 2 speed work?

It works amazingly well. I was a skeptic before trying it, but I just had to get one (I am a gadget FREAK). The thing has adjustable shift points, based on RPM, not load. The shift is very solid and it makes the coolest sound when it shifts. It really does make a big difference as you can have both good acceleration and good top end.

posted byAussie_Man:
Does that ever mono or wheel-stand with a higher torque motor? Looks pretty cool.

No wheelies. The reason drag cars have long chassis is to (hopefully) avoid wheelstanding. I MAY be able to once I get the foam rears, but I kinda doubt it. Like I mentioned, I over gear it quite a bit. This kinda removes any wheelie possibilities :). I am not sure what "mono" is, but it does have tendency, under hard wheel spin, to get up on one side. Kinda scary when it does that because those tires are carrying a bunch of rotational energy !

Posted by illbreakit:
The really short chassis would make a cool one of a kind mini. Gona hafta try that one day, maybe at 3am eh, jeepinator

Yes, exactly ! I did put the really long XXT arms on it, and made a complete running vehicle out of it (I had to use my XX4 saddle packs and stack them up as only 3 cells will fit lengthwise!). I did this just to see how silly it would look and drive. I should have taken pictures. It was FREAKY looking. I think it was almost twice as wide as it was long !. I do want to put some smaller parts on it and make say a 1/12 scale dirt racer. Would be cool. If I do I will be sure to post something.

Posted by ZenLosi
Jeep, how did you join the halves together?

I originally cut them in half with skill saw ! Heheh, no joking. It was one of those cordless units. I bought the finest tooth blade I could find to do it. Luckily, both cuts went very well and were nearly at a perfect 90 to the chassis. I then finished the cut edges with files, sandpaper, etc. To glue the pieces back together I placed a big piece of wax paper on my work surface. I then put a very small bead of cyanoacrylate (heh, i.e. tire glue, super glue, etc) along the edge of the cut. I applied glue to only one side. I then placed both chassis halves flat on the wax paper and slid them toward each other until they were mated. I pressed the halves firmly together for a period and then just let the glue slow cure for a few hours. I got kinda lucky really. Both chassis turned out amazingly well. I mean you almost can't tell they were glued. And the connection is extremely strong. On the long chassis I added 2 little graphite pieces to make sure it held together. You can see them in the pics.

Again, thanks for the encouragement !
I love just messing around with RC stuff. I like building/racing "normal" kits as well, but I spend a lot of time inventing new ways to have fun with RC.

[ 05-19-2001: Message edited by: jeepinator ]

[bryceanator]

nooooooo! you sacrficed an rc car and a double x you should be ashamed

THAT YOU DIDNT PUT A BRUSHLESS IN THAT BAD BOY cool very cool i run a xx beat some xxx with it too but mines quite tricked out what is the name of her?

[jeepinator]

bryceums,
I have considered it as I own an Aveox 1409/3Y and controller. However, the inherent design of brushless motors is not condusive to accleration.
Huge holding power (will keep the same RPM as load increases), is these motors big claim to fame. The rate of acceleration is actually calculated by a computer in the controller. In normal motor designs, when the ESC is given the "full throttle" command the batteries are essentially direct wired to the motor. Not so in brushless land. The controller knows where the armature is because of the Hall Effect sensors in the endbell. The computer than compares the current RPM and power output with the requested power output (where your finger on the controller). If more power is requested than is being delivered it advances the rate that the coils are being fired (advances the timing essentially). The coils are fired in a circular fashion and the magent follows the field created around in circles, creating torque. If there is equilibrium, the rate at which the coils are fired in a circular fashion remains constant.
Why did I say all that ?
To illustrate that there is significant lag (delay of requested power) with brushless motors. Delay or lag is something you do not want in drag applications !
Here is a summary of what occurs when the vehicle is at a dead stop and you "floor" it:
1) Controller sees equilibrium (even at a dead stop)
2) Controller senses taht requested power exceeds delivered power
3) Controller starts advancing the the firing of the coils in the can of the motor (where the magnets are in normal motors).
4) Hall Effect sensors give controller feedback saying that indeed things are moving, and here is how behind the armature is from the coil firings.
5) The controller makes an assesment as to whether the timing accleration is too great (trying too hard), or or if requested power still exceeds delivered power.
6) If requested power exceeds delivered power go to step 1. If they are equal, do not change.

This feedback loop and "sense --> decide --> act --> sense --> decide --> act" thing is what causes brushless designs to accelerate with less vigor that brushed designs.

This is probably not worded correctly, confusing, and maybe a little off, technically, but the concept is accurate I think.

I am actually open to discussion on this. If someone knows more, or is more capable of describing technical things please come forward !
As a disclaimer, I am not an engineer, have not been trained in BL motor design, and could be way off. I have taken apart brushless motors, put an osciliscope on the leads, and have a TON of time playing with them. All of this is based on pure speculation, but I would put money down that it is very close.

[bryceanator]

i understand what your saying so its like the motor has a slow reaction rate then put a 6 turn one wind in there they are high speed motors or try a trinity drag works :D

[HumbleEagle487]

Hey jeepinator, speaking about having fun by inventing new things. I'm thinking about buying a electric pede and then changing to a rustler chassis and putting a tc3 4x4 drive train in it. What do you think?

[jeepinator]

I think you are being a wise guy ;)

[Railman]

Jeep, What you did is very cool. It's always a big plus to take spare parts & make it into something unique. I like your input on the brushless motors & it makes sense that they may have their drawbacks, but time will soon tell. I do believe that simpler is still better in most situations. I like your conclusion on the higher wind motor with the 10 cell set up. It proves a point that many just don't get it...that is that if you increase the voltage enough the wire/windings need to be longer to get max available power. I think I've got a Tekin that will do 10 or 12 cells also. I'll have to check it out. Maybe I'll glue up a couple old XX chassis & get out the hole saw to lighten up. I think we have 3 XX chassis laying around somewhere. I wonder how about 20 nicad aa cells with lower gearing would do in something like that...probably throw a winding, bad idea I guess. Again Jeep nice job! :cool: :cool:

[Rc1oGtMaN]

That short chassis with the long a-arms must have handled awesome. If your theory is true about the brushless motors staying at a constant RPM rate, than your two speed tranny wouldn't switch gears, since you said it changes depending on rpm, not load. Awesome work man.

[WhoKnowsWho]

Wouldn't the GM-Racing brushless motor work a bit better since I believe they don't have sensors to monitor RPM and such? Or maybe that was another one...

[jeepinator]

Railman, great minds think alike :p

Rc1oGtMaN, actually that setup handled like dog doo. I am going to do it again and take pictures. I will post them and you will agree that there is no way it can handle well ! :p For one, I could not keep the front wheels on the ground. The chassis was so short that even a micro blip of the throttle made it do a revers endo ... was fun to play with though. In regards to the shifting thing, you may have a point, but what I was trying to say may not have been worded very well. The brushless motors still have variable speed, still have to spool up, and still bog under load (like normal motors), it's just that they are better at keeping the same RPM as the load increases than brushed motors. This is why they are so much more popular for airplanes. They swing a prop that pretty much has a constant heavy load. So, the shifter would work, but the shift points would have to altered quite a bit.

WhoKnowsWho, unfortunately I am only familiar with my Aveox. It is the only brushless motor I have even seen in real life. I have had it since '95 or so (that alone says something very cool about brushless designs). I doubt, based on my rather limited knowledge, that there is any other way to do it. I suppose the controller could monitor the CEMF on the power leads and use that in it's calculations of where the armature is, but it seems like a stretch.
I am no electrical engineer, that is certain ;)

Thanks again for the kind words. Soon I will be posting another crazy project I did. you will like it just as much, I hope ;)

[Rc1oGtMaN]

You're like ten steps ahead of me on everything I said, jeepinator. Maybe you could add some weights to the front of that short chassis to try and keep it down. I didn't even think of it coming up.

[jeepinator]

I bought some of those Jaco foam tires for the XXT and put them on this. WOW, much better off the line.
I also put some real RC drag car front wheels on it, but they just looked stupid so I took them back off. The foam rear tires saved a whole 3 ounces in wheight. And that is rotating mass mind you.
My HPI 2-speed pinion is still lost, but I just ordered a new one. HPI is selling the associtaed version for 20 bucks on their web site !!!! Wow that is cheap. I bought my first one for like $55 or some crazy thing.
This thing flat hauls !
Even my adult neighbor friends (who usually look at me a little weird when I bring my "toys" out :rolleyes: ) commented how downright stinking bloody fast it was.
I had to go to the doctor because of whiplash just driving it up and down the street :p
I am devising a way to put my G-Tech Pro ( http://www.gtechpro.com ) in the car so I can get accurate 0-60 times (assuming it goes 60, which it just might). The two speed should help alot. I'll keep you posted ...

[tejotasbd]

that looks too sweet:-)

how did u add a "homepage" link? my profile doesnt have an option to provide a homepage..........

[CBlakeNS]

Dude that soooo awsome!!!

[broken_parts]

what 2-speed and how did you get it to work? will it fit a traxxas?like a srt

[jeepinator]

HPI 2-speed. Made for the Losi XX tranny by HPI.
I got it to work by installing it :rolleyes:

No, there is no version for any Traxxas kits. Only the Stealth and the (probably discontinued) XX tranny's. Well, there of course is the HPI 2-speed for HPI kits ...

[Jo_bomb17]

And yet ANOTHER MASTERMIND Jeepinator creation!I think Jeepinator was really the one to invent electricity!He can invent anything else!Nice job AGAIN Jeepinator! :D :cool: :p

[jeepinator]

OMG dude !
Thanks a ton. That was a very nice compliment !

Heheh,we need a blushing smiley! http://www.theshreves.com/pics/smiley/eek2.gif

[Jo_bomb17]

No prob Jeep,anytime!I accually have compliments on sale for VERY cheap right now, there free!LOL :D :p

[SteveP]

Jeep - VERY trick. I like it! :D

[Rc1oGtMaN]

Jeep, did you ever get the HPI 2 speed tranny? I'd like to see some vids of your car in action. Oh yeah, do you put a body on either of your FrankenXX's?

Mark O.

[jeepinator]

Ya, I got the 2 speed put on there. I also got those cool foam tires for the XXT from jaco on there.
With that combination it was REALLY fast. It will full on spin those foams into oblivion if I let it.
I still have to roll on the throttle a bit right at the bottom. I resolved most of the wheel spin by rebuilding the pack to be "stacked" so all of the cells are in the back.
It's top speed is so fast that I actually get scared driving it. I mean like 70MPH. When it goes by me I literally lose it for a second (sight wise).
A few weeks ago I turned it into what my buddy called, "clean up on isle three please". Heheh, there were parts everywhere. Stupid road reflector !
It is currently in a state of disrepair. I need new dogbones. One of my custom units got trashed. I think the Street Weapon ones will fit, but I have been too lazy :(
As far as the body goes ... yes I HAD one, but it disapeared ! It was a XX and a JRX Pro SE body taped together. Believe it or not it looked darn good !
Here is a pic:

http://www.theshreves.com/rc_stuff/images/drag4.jpg

PEACE

[jeep groupy #1]

Nice car!

[Kodiak31415]

This may be stupid this may be funny it may be both. Why don't you make a "limo" body for the car... Yeah a 70mph 1/10 scale limo.

[jeepinator]

That's a great idea.
The only problem is that I don't have a vacuum former thingy. I got to play with one at a customer of mine once, but that's as close to making bodies as I have been :)

[Skribble]

Ask FrankW to make one for your Birthday! :D You ever get the Foams for the rear? Lol ..

[BAC5.2]

jeep jeep jeep.... that's freakin nuts-o man.

way to go on that.

your brushless explanation is dead on (just by basic theory on how it works, ive never taken apart a system, nor even looked at one). as the computer senses the request for more power, a series of "if-then" sets are evaluated and it figures out just what the motor is doing, so, while the motor actually COULD accelerate faster than a brushed type, it doesent because of the computational speed..... i think.

Jeep, your a smart enough guy, i mean, you drive a jeep (and were smart enough to get the trusty 5.2L, lol). so please tell me that you understand the concept of Centripetal force (NOT centrifugal). please tell me that im not the only person on this board that has some type of intrest in physics and the real way things happen......

folks, centrifugal force isnt real, it doesnt exist. there is no force pushing the water away from your arm in the bucket, there is a force keeping the water in. its called Centripetal Force folks.

[M.R. Ogle]

Now forget about all this brushless crapola and call Steve Saik for a REAL MAN'S MOTOR!!!! You know... immortalforce-dot-com...
How about a quad-neodymium "Sanitarium" model Top Fuel motor??? ;) :D