Spring Powered Dragster

I'm not sure how your dragster is constructed but here's how I'd do it. I'm assuming this is a toy. Using a spring similar to a screendoor spring except shorter. Attach one end of spring to front axle. Attach cord (kite string would do) to other end of spring. Wind string around thread spool with rear axle going through spool (interference fit) cut notches in one edge of spool and install a triplever on body to make contact with notches in spool. Be sure to weight handle of trip lever to keep it in the released position when dragster is in motion. Rolling dragster backwards will wind up string, thus tensioning spring. When the spring has reached it's maximum travel (end touching spool) set the triplever. Your dragster is now ready to go.

Lets also keep traction in mind. If tires, weight on tires, etc., is not considered, this could be just an "in-place" burn out with little forward motion.

I do think your idea is a good one overall, though.

-John

Thanx JohnJohn,

This actually sounds like it might be fun. Something to while away some time until spring arives. I just might put one together. I'm thinking 1/24 scale. A 20ft course should be about right. Should be able to time it with lazer pointers and sensors. It should run on a track with little walls or perhaps a pin in a slot. Anyone care to race?

You could also use a "constant force spring" (sometimes called a clockwork spring).

Hello Guest.

Try Google Search: Clockwork motor = Results 1 - 10 of about 316,000 for Clockwork motor. (0.30 seconds)

There are plenty of folks willing to accept your $$$ in exchange for a suitable clockwork motor.

Kind Regards....

(As you know) model prop planes use torsion rather than extension to store energy in rubber.

I realize that the gearing would be harder in this app, (and you'd have to have a gearbox with consequent losses), but I wonder if there's any fundamental reason why one method should store more energy than the other?

One advantage of the torsion method would be that it would be easier to wind up (with eg a wheelbrace).

Any ideas, anyone?

Ha good Q !

I'd guess that torsion has greater frictional losses, but a straight strech requires a V long vehicle or pulleys which have losses. So it's probably 6 of one vs half a dozen of t'other. For a car the straight pull gives an axle rotating in the right plane. Whereas for a propeller the torsion gives the right axis of rotation.

Again it's a dragster so short duration is ok. For a distance car I'd guess you'd have to go for torsion.

If we could decide on a standard rubber band we could have a 'CR4 how far can the car go contest'.... prob would only get 2 or 3 entries tho' (like my damned junk yard battery....)

Del

Yea, I guess your point about the rate of energy release is the decider. 'Frinstace, an elastic-launched model glider uses extension, & all the energy is released in one whack on launching.

Good point also about the ease of driving due to orientation of axes.

Wonder if there's a source of ready-made 'proper' fusees out there anywhere? Don't suppose there's much call for them these days! Might get away with a conical drum - but the winding goes on the 'wrong way' (larger diameter to smaller) to make it easy to wind without a fancy guide mechanism. I guess a conical drum with a spiral groove turned in it would be easiest to make - tho' it'd still need a fairly fancy lathe.

The simple stepped axle works pretty well, and it's easy to experiment with by padding it out with masking tape...or some such high tec' method .
You get as many turns as you like on the big diameter, it doesn't matter if they go over eachother, then you step down onto the thin axle as the tension increases, the hard bit is judging it so you don't lose it all in a mad wheelspin.

I hope we get to see some pics
Del

Right then, if you're going to make one, then I'm going to make one! Game on!

of course there is a reason that the inferior technology is used over an actually superior technology...It's called the politics of money. It is a force of nature that us sheep have supported for millenia...and will continue to support through stupidity and gulibility...as has been handed down by the ages...Baaaah

... but in this case, which is the superior technology?

Thanks, Del, this kind of post is precisely the reason I love this site!

Screen door spring? Nah, I'd go with a coil spring.

You guys may just be mucking around with ideas that are old hat, but to me this is an education. Thanks.

I'm sorry, but I disagree with all of you... I don't think spring will do anything for the speed of this dragster. Plants don't grow that fast. Even if you plan to move it in the spring, at an elevation, latitude and with a nutrient base that promotes optimal growth, I don't think you're going to get more than .0038 mpd out of any plant material. It also limits your growth phase and acceleration.

Powering a dragster by seasonal growth is probably not a consideration unless some serious genetic engineering goes into the plants themselves...but we may be able to gain additional energy if we combine spring with summer and optimal solar productivity.

For those of you that think I'm a complete moron...let me tell you, I haven't even begun the journey...but think definition.

It isn't only the sap that is rising in spring, think of horsepower and think reciprocating piston, for short bursts, this could be an interesting power source, but do not discuss in front of Henry, he's a gelding.

I made a variable drive for a model car some years ago. That particular car was powered by a solar cell & ran on a straight track for a competition at an engineering show & we reached the quarter finals, not bad considering that companies like Rolls Royce made it their apprentices project and threw money at it.

Anyway, the drive I made consisted simply of two pulleys like a cassette tape, one attached to the motor, the other to the axle. As the tape wound off of one pulley & onto the other you got a constantly increasing drive ratio. Similar to the stepped shaft & fusee suggestions but easy to make. I turned the pulleys from Delrin & used PCB layout tape with the adhesive stripped off for the drive tape (that alone dates it, when did you last lay out a PCB by hand).

The drive had to be rewound after each use & you have to be sure that you have enough tape on the 1st pulley otherwise it becomes a very fast reverse gear. As suggested earlier, we used foam slot racing tyres & doped them to get maximum grip.

If you can consider air a spring, would a hand pumpable pressure cylinder do better than a hand wound metal or rubber spring?

Yes, but productivity with that model would depend on the celibacy coefficient, relative hand strength and visual stimulus.

Interesting!

Question now is what's the best way to convert the stored energy to kinetic?

Piston engine, Wankel, turbine, jet, single pneumatic cylinder working like a bit of elastic contracting ...

Also, what's the easiest to make?

[May also get bogged down with H & S issues - receiver would probably have to be pressure-tested if used at a public event!]

Dammit - there's paying w**k to do!

LOL, engine determination? I think we're talking about stick and rubber stored kinetic energy...I'd like to see you stuff a rubber band into a wankle or starrotor and draw any energy out of it. While My Inane Suggestions (See Tom's Completely Reprehensible and Impractical Thoughts), but a wankle still needs a pressure differenctial to activate

.. just tossing around a few ideas triggered by suggestion in #19. Anything involving air being pumped is, I believe, going to give us a pressure differential.

there is one other alternative...using the "spring" as a force to slam two subcritical masses of uranium into a critical mass and cause a cascade reaction, a heck of a lot of extremely dirty energy, and way more power than we need in this contect. But, technically it could happen.

How about a sausage balloon in a drain pipe body! The balloon can be activated when the spring has pulled all the line off the rear axle! If the end of the line had a small ball attached, this would pull the loose knot tied round the balloon releasing all that air that is directed at the fans attached to the rear axle! Just out of curiosity! How big is this dragster? Or am I going off on one?

Hi All

For that really interesting dragster fit rear facing 12 gauge shot gun cartrige with the shot removed and let the sring initiate Newtons law

I reckon it'd go faster if you left the shot in !

This is my go faster system.

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I see you've attached a cannon! If the donkey had roller boots it may just work!

Try browsing the site www.modernmechanix.com . Lots of old popular science-esque articles that have been scanned and posted on the web, a number of which show how to build small dragsters and go-carts in the same vein you're shooting for (start with http://blog.modernmechanix.com/2008/02/18/rubber-bands-drive-this-baby-auto-three-miles/). You might be able to see what was done in the past and find simelar modern parts. Quite possibly my favorite website ever.

Avery Montembeault

I had a thought just after I posted the above - why not just use a bicycle sproket/chain assembly from a 10 speed bicycle and use the derailer to switch gears? It would be incredibly cheap and easy to do, not to mention you gould probably choose a gear set that works best for your application. If you can figure out a way to put a clutch in the system, I bet you could launch that baby pretty good.

Avery

Now you are torquing! Thanks for the links.

BAB

For some reason I thought the OP had a "small" (kid type) dragster in mind, something on the order of a Pine Wood Derby type car. If so, I think your bike derailleur idea may not be appropriate (unless machined/scaled down).

However, if you really want to consider such an option, I think the fusee suggested by Del would do the same thing as what you suggest.

Okay, folks when you come down to it, it's the same old thing; weight vs hp vs traction. I propose that 90% of the weight (and horsepower) be supplied by a 1950 Oldsmobile front suspension coil spring.

An axle will be center mounted within the spring, i.e., the spring itself (with appropriate soft rubber coating will act as the rear (drive) wheel. For those imbibing and having a "not so good" picture of the car, the spring is lying with it's major axis parallel to the drag strip surface and perpendicular to the axis of the car.

Okay, get this now, by using a tensioning device reminiscent of Del's crossbow cocking device, we (through GREAT effort retract the monster spring) allow it to expand in a controlled manner thus providing mobility (expansion) and forward motion (spring is a wheel).

-John

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Incidentally, the axle (which is within and parallel to the axis of the spring) is splined such that the contracting/expanding spring can do its work, i.e., propelling the dragster. One end of the spring has a matching/machined splined disk (welded to it) which slides on the axle and provides spring/axle mating.

Granted this may be more horsepower than a "little" car like this can handle, but lets think big! Perhaps Kris could stand on it to provide traction?

Given my choice I would go with the Napier Lion as a power source. Maybe a little overkill for this project.

-John

One important further note: The other end of the Olds spring/wheel (not the end with splined disk) is FIRMLY attached to dragster! Just thought I'd throw that one in for the doubters and confused (as I usually am).

Help! I'm on my back and I can't get up!

Doesn't it need some freewheeling capability?

Nope! When the spring has expended all its energy (unwound), the forward momentum of the dragster causes a reverse wrap of the spring which, conveniently, returns the car to the starting line (well, almost anyway).

In post #36 I said the spring itself would act as the wheel. However, in the cold hard light of day (and coffee) I decided that the spring would only move lateral to the car, and only slightly at that. So not a good, clear idea. The tires/tyres would of course need to be slightly larger than the spring.

OTOH, suppose we assume that the car only moves in a lateral direction relative to its longitudinal axis. We place two monster springs- front and rear- in place of normal wheels and they actually contact the surface of the track and act as direct propulsion. To visualize it, picture a road surface compactor (steam roller) where the two rollers are monster springs.

Now, since the springs expand or contract, depending on how the operator winds them, and since they are in direct contact with the track, when the unwind trigger is pulled, the car moves, i.e., jumps sideways. Again, the springs are coated with "flubber™" so we have a unique, unbeatable traction situation (if the car doesn't move, the track will).

The car is placed at the starting line perpendicular to the finish line. When the light goes green we put the pedal to the metal (pull the trigger) and off we go!!!

Incidentally the finish line is six inches from the start line.

<walks off stage bowing profusely, soliciting points for innovation>

Jonhjohn,

Where do I begin! I think this will describe it better than me!

http://www.youtube.com/watch?v=ZgxYEPhSzsc!

LMAO!!!

Yep. My idea is in that same category, no doubt.

I was told you can't weld to spring steel? Is there a way?

I believe you can... but it will spoil the temper where it is heated, a spot weld might do nicely?
Or a good old rivet?
Often springs are just hooked on, or bolted on...
Its about designing the part and it's method of attachment as an entity.

Del

I was assuming an unmanned (un-catted? un-peopled?) car about 24" max...

It's a bit like that old poem ..

There were six men of Hindoustan to learning much inclined,
They went to see an Elephant, though each of them was blind....
etc

Come to think of it, there's a lot of threads like that

Del

Reg. uninvited Guest with a lot of Cornie Experiences. Reply to:Spring Powered Dragster: Now your talking Teenager Toys, with a '50 Olds coil spring. In '58 I owned a 57 delta 88 Olds. Back to the Spring Powered Dragster---- Use the Overhead Garagedoor spring idea. Scale down to the size & weight you're thinking of. Like the screen-door-spring slid over a 7" Raintrough Spike, for axel, 2 hockey pucks friction fit, for wheels. You might want a Drill Press to drill 1 hole to lock spring end to axel. All suggested parts are in my Junk Bin(except the drill press.) I'll Like, I usually do, be watching for which idea or ideas, you try. Carl, Retired from Carl's Computer Cartoons.

You actually have a 50 Olds front spring?

How much ya want fer it?

We had school competitions over her using "rat trap" as the base for a standardised dragster.

Lots of alternatives for slowing down the stored energy to stop wheel spin.

Springs do work (very well) and if you're game you can re-assemble with another turn or two of pre-load and have significant advantage over others.

This thread has seen a lot of action. I guess a lot of us still want to play with toys. I'm wondering, however, what has become of the original guest who posted this. Maybe they are sitting back getting a good laugh. Maybe you, mystery person, can tell us what exactly it is you are working on. Is it a toy or an actual full size spring powered dragster or somewhere in between?

I must say though, this has been loads of fun so far.

A long time ago I read an article on failed attempts at the land speed record. One that comes to mind was a windup full sized vehicle that was assembled by the country of Switzerland. The article had to be from back in the early sixties.

I would like to draw this, unfortunately do not have the time tonight
perhaps tomorrow - but I will try to describe a "picture" of it.

Imagine 2 sealed containers, upper and lower. The water is initially
put in the upper container and is released through a variable valve
(shielded jet) into the lower container, safely keeping the water.

The upper container is pre-pressurised either by pump, cylinders of gas,
or, preferably, a large spring loaded piston in a tube. (eg similar to air rifle)

The (highly) pressurised, small, jet of water is used to drive a "pelton" style
wheel for the rotary motion, which is applied as a direct drive to the
wheels of the contraption. (we have motion, and not too many losses)

As there are no obstructions, eg hills, etc. no gear changes are needed,
and, the speed can be adjusted by varying the opening of the variable jet.
This ensures the "vehicle" reaches the 250ft limit; probably at a fast speed!

There are only 2 moving parts, the spring loaded piston (for air pressure)
and the "pelton" style wheel for the direct drive. It would go like a rocket!

I hope this helps. (sorry no pic.)

jt.

My beautiful gold pocket watch; it belonged to my grandfather, and,
on his death bed, he sold me this watch.