When an Engineer gets a Micro Scale

[Aaron]

An e-mail ausmicro.com received a few days ago, just thought I’d share!

—
Hello out there,
I stumbled across your interesting web site about miniature r/c cars and thought you may be interested to hear about my Dick Smith purchased ( under intense pressure from 9 y.o. daughter !) Micro Racer Subaru and PT Chrysler. Out of the box they were just plain ‘orrible, I felt like an idiot for buy useless crap, the automotive aspects of construction and application were, I guess equal to the A$26.00 price tag, however the controller and receiver are of excellent design and this prompted me to attempt a complete reconstruction. Fortunately I own a precision micro engineering business ( lucky me!), the first modification was to improve the efficiency of the transmission, the original reduction escapes me at the moment however I went for 11-1 to see if the motor drew less current if running at high speed, the gear profile is now 120 d.p. if that means anything( about half the size of the standard tooth profile) the motor pinion is 2.54mm dia and 10 teeth, a lay shaft had to be used unfortunately to enable a differential to be fitted, the diff’ is only 8 mm in dia and 10 mm long, housing the very small spider gearing and half shafts, it runs on two 6x3x3 ball bearings, all the gears are steel except the final drive which is brass, the layshaft spindle is a .6mm dia chromed sewing pin, the motor/ g/box housing is in three segments and made of acrylic.The original g/box housing was cut off and the new one screwed in place, hair/fur and fluff resisters are fitted behind the wheel rims ( they look like disc brakes but don’t rotate).
The steering system was modified with more sewing pins for king pins and steering arm links and run in brass bushes, the toe in-out is adjustable for each wheel and the castor was reduced to 1.5mm, the front axles are 12 b.a steel screws and the rims run in brass bushes and also fitted with Delrin fluff resisters.The suspension is retained. New rims were turned up from white Acetal with 8- 2mm dia holes in each, tyres were made from neoprene and ground to size with a diamond grinder.
The contoller levers were shimmed out slightly and realigned, and a resistance spring was fitted to the turbo function making the action much harder and avoiding boost at the wrong moment.
All this increased duration up to 8 minutes and on one occasion the PT managed 14 minutes! ( 4 metre long course on polished lino floor with no boost) The steering is dead straight and almost the same in reverse with no castor effect wobble, turning circle under boost is 50 cm normal power – 40 cm and 15cm on over-run (the differential reduces “crabbing” resistance and allows this curious effect to occur) Top speed is 6.5 km/h.
—

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Site Owner Guy.

[merc-blue]

wow thats cool.. email they guy and get him 2 join !!!!

if you mysterious man have joined or join and read this email me i think i got somthing u may be interested in

Edited by – merc-blue on 14 August 2004 18:55:03

[betty.k]

sounds impressive!:p love to see it sometime:8ball:

[z-beam]

interested indeed. i wonder how much it would cost to get some cars “fixed” by this guy!

or even a few differentials made to tomy standard gear spec. would be awesome.

did you reply to his message yet Aaron?

[jamiekulhanek]

Holypoop on a stick, i want a diff NOW!!!

hmmm, ball diff anyone??

[rashumble7]

WOWWWW:shock: Put me on the list, i would love to see some pics.

[HACHI-RYOKU]

Ditto. I’ve been wondering how to put good castor in these cars. That’s one of the things that really screw these cars up. Without good castor, they wobble all over the place. A few of my cars just happen to run really straight, but for the most part I have to work really hard to get them going straight.

[betty.k]

pardon my ignorance, what’s castor?:8ball:

[PandaBear]

Quote:

pardon my ignorance, what’s castor?:8ball:

The axis that the steering knuckles operate around, on the BCG is usually 90degs perpendicular to the road surface.

If this axis is leant backwards (at the top) to less than 90degs instead… the castor effect will induce a self-straightening force when going forwards.

Without castor it’ll be very hard to balance a pushbike. And it makes it nearly impossible to balance it riding backwards.

[betty.k]

aha! thanks for that. so why do we see extreme castor on offroaders more than street cars?:8ball:

[jamiekulhanek]

i believe too much castor sacrafices cornering ability, also, the more castor (negative castor??) the less likely it is that the vehicle can be bump steered…

[TallduDe]

is castor the same as camber, as in 1.5 degree camber for the front wheels able the tire to be flush with the road surface while cornering?

im most likly wrong…..again :smiley2:

[betty.k]

camber is the angle at which the wheels lean towards the center of the car.:8ball:

[peteWah]

Or away from the center:question::8ball:

[betty.k]

true, that’s negative camber. i’m not sure what you would want that for though:8ball:

[Super Max Power]

Camber is the angle of the wheel to a vertical plane. Ie. if the top of the wheels are closer together than the bottom it is negative camber.

This helps the car turn – because as you turn the wheel ‘rolls’ over and you expose a greater area of the wheel to the ground.

Castor is the amount of camber while you turn. With Castor you can have 0 deg camber when going straight (great for breaking) and more negative camber the more you turn into a corner (great for cornering).

So remember – nobody likes a bogan.

[betty.k]

gots to correct you there max, when the top of the wheels lean inward, that’s camber. when they lean out that’s negative camber:8ball:

[Super Max Power]

Camber is the tilt of the tire as viewed from the front of the car. If the top of the tires lean toward the center of the car then you have negative camber. If the top of the tire tilts out away from the center of the car then you have positive camber.

http://www.racingpc.com/tips/what_is_camber.htm

and picture evidence
http://www.maximummotorsports.com/images/large/CasterCamberToe3.jpg

Should I keep going?

[icebreaka]

I agree with betty.k .. when the top of the tires lean toward the centre, thats positive camber..

leaning away is negative?

[betty.k]

i’ll bet my left knacker i’m right. cambered knuckles sold in positive degrees lean towards the middle. i’m pretty darn sure i’m right.

are there any situations where outward leaning wheels are needed?:8ball:

[peteWah]

Go and have a look at those links that
Super Max posted…YOU ARE SO WRONG
You can eat my left testicle if i have to get it removed in the near future… (Ive said to much)

Betty; Uh, you mean positve not outward leaning dont you, well anyway your wrong :smiley2:
Nascar, IRL and CART do it every day of the week and they only go left, Its so obvious
Oval racing, Think about it… Go back and READ those links :smiley2::D:D:smiley2::p:approve::8ball::dead::question:

[TallduDe]

yeah i thought negative camber was the top leaning in, i only know this coz my datto has it on the rear wheels……..something about wornout suspension i remember being told LOL

[peteWah]

Are there any situations where outward leaning wheels are needed?

In everyday driving it happens Betty, Say if you had a car steering in full left lock,
The wheel on the left would be pointing outward
(bottom of the tire away from the center)

And the wheel on the right hand side inward (top of the tire towards the center)
All this while looking at the front of your car…

You can test this theroy if you want by jacking up the front end of your car and turn the wheel all the way to the left… what happens?

Need i say more

[peteWah]

Quote:

yeah i thought negative camber was the top leaning in, i only know this coz my datto has it on the rear wheels……..something about wornout suspension i remember being told LOL

SWEEEEEEEEEET duDe

[icebreaka]

ok my bad … hehehe.. negative camber is top of the tires lean in..

i was jst confused because in rc mart and toyeast they sell 1,2 and 3 deg camber and the tops lean in .. so yehs..

link:
http://www.stockcarracing.com/tipstricks/31519/

[betty.k]

max, pm me your address. i owe you 1 hairy sack of man milk!:blush: i too was going with the info from aftermarket z knuckles. always learning!:smiley2:

so given the correct info, what i meant was is there any driving situation that calls for positive camber?:8ball:

[peteWah]

Nascar i told you :evil::smiley2:

[peteWah]

If you dont learn somthing new every day.
You aint learning at all.:smiley2:

[kevsta]

Yeah negative camber gets your fat wheels to remain under your wheel arches brother.

[Super Max Power]

You can keep your hairy sack of man milk Betty. No apology is needed ? getting the word of the bogan on the street (or internet) is enough for me.

Positive camber is almost never used for front wheels, except in the case of nascars, champcars or any other ring runner (and only on the inside wheel). Like pete said.

However positive camber can be seen at times on rear wheels. This depends on the suspension setup for the car. A perfect example is a VW bug. Next time you watch ?Hebbie goes Bananas? check out how stupid the rear wheels look with the positive camber on those babies.

Oh yeah Datsuns rock – car and band.

Edited by – Super Max Power on 19 August 2004 17:48:28

[TallduDe]

okay this site tells ya everything

http://www.tirerack.com/tires/tiretech/general/align.jsp

also tells me how to fix my datto 1600 suspension lol

btw i love dattos but not the band :smiley2:

plus macguyvor rocks i never leave home without a swiss army knife never know when u might need to disarm a nuke……

anyway back to the original topic i wanna see this diff this guy made lol

[peteWah]

Wish you had a 1200 ?

[TallduDe]

dude i can barely fit into the 16 imagine me in a 1200! no room watsoever.

plus you cant compete 1200 in historic rallies, dats y i bought the 16 in the first place.

[Author]

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