[David Lawson]

Howmet

Have I missed something here. How do you ensure the motor/axle position for correct gear mesh at the very beginning as the rear axle tube prevents you from setting them up?

David

 

[howmet tx]

Hello David

I do a dummy set up with gears in place on the motor and an axle, in an axle tube, and offer them up together. If necessary you then put in shims between the axle tube and motor case. When you have a good mesh, take it all down and set it up again in the jig without the gears and hold the shims, motor and axle tube together with superglue until the main chassis rails are secure. But keep checking as you go, since there's always a little bit of movement available, and the whole caboodle isn't actually locked up in position until all the motor cradle is finished. Or ditch the whole idea of making it with the long axle tube and cut it to the right length first, but keep it in place in the chassis jig with spacers or collars. Tell the truth I do things different every time or I'd get bored. The eternal search for the perfect technique!
I rely on toothpaste more than I should though, probably.......
As usual, takes longer to say than to do.

Cheers

 

[David Lawson]

Thanks Howmet, now I get it.

David

 

[compound_goose]

has anyone ever strapped a model rocket engineto a slot car and ignited it?

would make a superb drag car!!!!!!!!

it could ignite the engine when u pull the trigger!

 

[bwaminispeed]

QUOTE has anyone ever strapped a model rocket engineto a slot car and ignited it? would make a superb drag car!!!!!!!! it could ignite the engine when u pull the trigger!
YES

Lots of smoke

 

[GRAH1]

QUOTE has anyone ever strapped a model rocket engineto a slot car and ignited it? would make a superb drag car!!!!!!!! it could ignite the engine when u pull the trigger!

one for you Difflock

 

[Difflock]

No problemo!

Yes, people, one of my other hobbies is model rocketry

A 3 - axle double decker bus model could accomodate a frighteningly large rocket motor (or two)!

Seeing as "D" class motors (not much larger than a shotgun cartridge) should be available for your local model shop (if they stock such items) then power to weight ratios can be impressive. D motors give a 6 lb initial thrust "spike" followed by approx 3 lb sustain. Mind you sustain is a bit of a misnomer as all the fun is over in less than 2 seconds!!

Might I suggest a Fiat 500 with a sacrificial flap covering the engine bay and a nice A or B class motor?

Mark.

 

[McLaren]

I made a rocket powered car once. Posted details on SCI.
Needless to say it went horribly wrong and I do not suggest it to anyone.

Details (someone would have asked...):

My friend and I decided that our last project (a taser gun) was getting tiresome and painful. So we embarked on our second most explosive project yet... a rocket powered Lego car. *cue dramatic space shuttle music* After carefully glueing all of the bricks in place, we wedged the rocket motor in place (a 'C' sized one, I believe) and took appropriate precautions by taking it to a road that neither of us lived down, and we were set. I crouched a good 2-3 feet away from it (limit of ignition wire) while my friend waited 20 metres down the road waiting to collect it (keep reading, he doesn't loose and eye). 3 - 2 - 1 - and simultaneosly, my friend and I remember something... I turn the key... it was the secondary charge.
Difflock will tell you that the secondary charge on a rocket engine is there to blow the parachute out of the top of the rocket just as it begins to descend.
So the car begins its journey, "surprising acceleration" I think. About 5 metres and 0.2 seconds away from me it leaves the ground. About 15 metres and 0.5 seconds away from me, my friend has already hit the floor (face up of course) and about 2 seconds later... BOOM! Houston we have a problem... it seemed like thousands of Lego bricks were raining down on us, but we didn't wait to see the last of them, we were off...

Again, I must strongly suggest... oh sod it, try it if you want, it was very funny...

Lotus

PS. Sorry for the article above... I must be a 'closet novelest'... Massivly off topic but amusing I like to think...

 

[Difflock]

QUOTE (lotus03 @ 22 Feb 2004, 11:18 PM)Difflock will tell you that the secondary charge on a rocket engine is there to blow the parachute out of the top of the rocket just as it begins to descend.
So the car begins its journey, "surprising acceleration" I think. About 5 metres and 0.2 seconds away from me it leaves the ground. About 15 metres and 0.5 seconds away from me, my friend has already hit the floor (face up of course) and about 2 seconds later... BOOM! Houston we have a problem... it seemed like thousands of Lego bricks were raining down on us, but we didn't wait to see the last of them, we were off...
ROFLMAO!! Yep, I would suggest either obtaining a plugged motor (available for boost gliders) or DIY with some epoxy resin filling the top of the motor.

Important safety consideration - always choose an area you don't live in! lol!

Mark.

 

[endbelldrive]

Rocket powered model cars...just saw them on BBC's Technogames last week. They were constructed according to these specifications:

http://www.bbc.co.uk/science/robots/techga...funnycars.shtml

Amazing stuff!

Bob S.

 

[bwaminispeed]

Mine was a half A engine strapped onto a Parma Flexi 4"chassis.We4 ran it on our 55' Commercial Raceway Drag Strip,with the igniter hooked to the Guide Flag.

Worked great,car was heavey,so performance wasn't stunning,but lots of Hissing Noises,and LOTS OF SMOKE AND FUMES.Took about 4 hours to clear the Raceway out.

I think it ran about 1.2 seconds,and the motor was still firing after the car was stopped in the shutdown area.

Was a good laugh,we didn't kill anybody,or burn the building down,but we didn't do it again.

 

[McLaren]

55' in 1.2! Wow! What times do the other cars run?

 

[Difflock]

QUOTE (bwaminispeed @ 23 Feb 2004, 02:25 PM)I think it ran about 1.2 seconds,and the motor was still firing after the car was stopped in the shutdown area.
The continued motor firing was most likely the bit of smoke put out to aid tracking the rocket in its coasting phase i.e. after the thrust of the motor has burnt out and before the ejection charge (if the motor has one) is fired. So relatively harmless

Note I used the word relatively

a certain degree of respect is still required before it starts raining Lego bricks!

Mark.

 

[bwaminispeed]

QUOTE 55' in 1.2! Wow! What times do the other cars run?
I believe the worlds record is around .28 sec.That is not a typo,barely a third of a second.terminal speed was I think a tad over 130 MPH(real MPH,not scale,just multiply by 24

)

Average runs are in the .6 to 1 second range.This is from dead stop to 55 feet.

 

[compound_goose]

now say we rig that ejection charge with some bangers and a water bomb full of liter fluid and place a brick wall over the bottom of my garden