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1/4 scale "JET" Dragster..!

Old 03-25-2010, 02:22 PM
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knobby1
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Default 1/4 scale "JET" Dragster..!

Hey All,

Just thought I'd let you know of my latest project, (I already have a 1/5 scale turbine powered machine), a new 1/4 scale after-burning turbine powered jet dragster, I have a new glass body, the same as Paul Songas' 1/4 T/F dragster body, from Mike at Legendary Reproductions....I have nothing but praise for Mike, he helped me no end to get the body to me here in Sydney, Australia, nothing was too much trouble for him.

A few specs for you. 1:1 jet dragsters normally run a 300" wheelbase chassis, somewhat similar to a T/F dragster I suspect, so a 75" wheelbase machine has been started. Weight of the car should be in the 8-9kg (17.6-19.8lb) range. The old 1/5 car was just shy of 7kg (15.4lb) fully fueled and ready to run. The engine of the old car was a 20lb (9kg) static thrust with ~30-35% augmentation giving a total thrust of ~27lbs (12.2kg).

The new engine will "hopefully" be an ATJ-240Ti turbine, this engine has a static thrust of just over 53lbs, add the ~35% afterburner increase and we should have somewhere near 70lbs (~32kg) of thrust @ full noise. There will be twin 30" cross-form parachutes and twin rear wheel disk brakes to help with slowing down duties.

To be honest, this car will never be able to compete with the gas and nitro powered machines of similar scale over a scale 1/4 mile but that's not what I'm really after, I just like the challenge of the build and seeing it finally run on it's own.

I hope to keep you all up to date of progress as it happens.

Cheers,
Smithy.
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Old 03-25-2010, 03:18 PM
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Lars from Norway
 
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Default RE: 1/4 scale

Exiting! Looking forward to see more of this.
Old 04-13-2010, 04:01 PM
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knobby1
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Default RE: 1/4 scale

Hey All,
Some progress pics of my 1/4 scale turbine powered machine for you, the car is ~90% complete and will be fired up for the first time this coming weekend..!

Enjoy.

Cheers,
Smithy.
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Old 04-13-2010, 08:27 PM
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Default RE: 1/4 scale

ORIGINAL: knobby1


To be honest, this car will never be able to compete with the gas and nitro powered machines of similar scale over a scale 1/4 mile but that's not what I'm really after, I just like the challenge of the build and seeing it finally run on it's own.
That's the spirit mate!
Too many people are obsessed with performance and keep comparing homebuilds to factory cars.


I like what I see but wanna see more.
Got any more pics of the frame without the body on, steering setup etc?


Good to see more dragsters too!
Almost makes me wanna build one.






Old 04-13-2010, 09:42 PM
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knobby1
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Default RE: 1/4 scale

No probs Dirty,

Enjoy..!
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Old 04-13-2010, 10:28 PM
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Default RE: 1/4 scale

Cheers mate.
That's pretty neat!



Old 04-14-2010, 02:03 AM
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Default RE: 1/4 scale

hmmmmmmm those rear tires are abit overkill eh?? being they're not being driven lol. car looks really cool man
Old 04-14-2010, 04:36 AM
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ORIGINAL: dealwithit

hmmmmmmm those rear tires are abit overkill eh?? being they're not being driven lol. car looks really cool man

Yes they are a bit of an overkill, I'll be fitting some "front" go-kart wheels and tyres soon, they should look a little better and be able to handle the high speeds I intend to do.

Cheers,
Smithy.
Old 04-14-2010, 05:52 AM
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Default RE: 1/4 scale

Nice one mate...I couldn't help but sing the song to myself when I saw this.....
"I'm a +!+$ and @$$ man, I'm a +!+$ and @$$ man!"
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Old 04-14-2010, 11:17 AM
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Default RE: 1/4 scale

Isn't that very hard to sing, Mudgy? This looks like a nice construction, knobby1!
Old 04-15-2010, 06:28 AM
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Default RE: 1/4 scale

Hi,

Lars, PM sent to explain the beer song.

Smithy, that's one wicked machine you got there. I just had a look at my car, it's 68 inch wheel base.
I also can get straight to 114.75 km/h due to the revs I'm getting with the std gears......change out 1 sprocket from 20T to 17T and I should be doing 135 km/h.

I still need to learn how to drive this, so I will be sticking to the current set up first.

Over about 100 Metres, how fast you reckon yours'll go mate? It will obviously eat my one for breakfast [8D]
Old 04-15-2010, 07:14 AM
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Default RE: 1/4 scale

Over about 100 Metres, how fast you reckon yours'll go mate? It will obviously eat my one for breakfast

Well you boys might just have to do a couple of runs to see?
I mean you're not THAT far from eachother, geographically speaking.......








Old 04-15-2010, 02:38 PM
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Default RE: 1/4 scale

ORIGINAL: Mudgy

Hi,

Lars, PM sent to explain the beer song.

Smithy, that's one wicked machine you got there. I just had a look at my car, it's 68 inch wheel base.
I also can get straight to 114.75 km/h due to the revs I'm getting with the std gears......change out 1 sprocket from 20T to 17T and I should be doing 135 km/h.

I still need to learn how to drive this, so I will be sticking to the current set up first.

Over about 100 Metres, how fast you reckon yours'll go mate? It will obviously eat my one for breakfast [8D]
Hey Mud,
My car has a wheelbase of 75", I used a "real" T/F car as a guide, they have a 300" wheelbase...so 75" is as close to 1/4 as I could get..!
Learning to drive these larger machines is certainly a challenge, especially since I use sticks instead of a pistol type radio, not enough channels on a pistol for my beast unfortunately, I need at least six, throttle, brakes, chutes, afterburner, hot streak and the failsafe, I also have a manual fuel shut-off just to make sure, so that's seven all together. My fingers certainly get a little "busy"[X(]

I'm guessing my car will do ~5.5secs for a scale 1/4, this is using the maximum thrust vs the weight of the car, this doesn't take into account friction etc...so 6.0 secs will be a reasonable guess. Top speed of the beast "should" be just shy of 180kmh at the 100meter finish line. The car is quite capable of going a lot faster but the question is ...."where?" apart from a proper drag strip.

Don't be fooled into thinking my car will beat yours over a scale 1/4, your machine will probably eat mine off the line to ~50m I guess, then mine will get some real air moving..! Then watch out..!

Try to gear yours to reach max rpm just as it hits the finish line, this way you'll get the best out of it, or you could get a two speed gearbox..!

Cheers,
Smithy.


Old 04-15-2010, 07:11 PM
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Default RE: 1/4 scale


ORIGINAL: Dirty_Vinylpusher



Well you boys might just have to do a couple of runs to see?
I mean you're not THAT far from eachother, geographically speaking.......


hmmmm, the mind boggles, but where to go?That would be cool, eh.

Knobby, how are you gonna get the chutes out without setting them on fire mate?
Old 04-15-2010, 07:32 PM
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ORIGINAL: Mudgy

hmmmm, the mind boggles, but where to go?That would be cool, eh.

Knobby, how are you gonna get the chutes out without setting them on fire mate?
Hi Mudgy,

I can "possibly" organise a bit of time down at the Sydney Dragway one day. I look after and maintain the Westinghouse J-34 powered track dryer at the track so I might see if the guys will let us run up the track a few times.

The fire should be well and truly out by the time the chutes are deployed, the leader lines will suffer where they droop over the tailpipe though, not much I can do about that..!

Cheers,
Smithy.
Old 04-15-2010, 07:52 PM
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Default RE: 1/4 scale

Couldn't the first 2 feet be made out of tracer lines, like from the bait'n'tackle shop?[sm=idea.gif]
Old 04-15-2010, 08:43 PM
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knobby1
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ORIGINAL: Mudgy

Couldn't the first 2 feet be made out of tracer lines, like from the bait'n'tackle shop?[sm=idea.gif]
Most certainly, I have 50lb strain tracers on it now, however, the exhaust temp is ~1800K at the tailpipe during a full rpm afterburn, methinks they'll still suffer a bit... That temp is plenty enough to boil your eggs at least.

Cheers,
Smithy.
Old 04-15-2010, 09:02 PM
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Default RE: 1/4 scale

1800 deg? = SMOKIN' !!
Old 04-15-2010, 09:18 PM
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Default RE: 1/4 scale

ORIGINAL: Mudgy

1800 deg? = SMOKIN' !!

This is a calculation of course[8D], there's no way I'm gunna stick my pyrometer up there when she's running on full A/B[&:] Besides, it only goes to 1000c.. However, the temp is in degrees K not celcius, my bad, just take 273 off and this will be in ceslcius. Still bloody hot though. The calcs have to be done in "absolute temps" or degrees Kelvin... otherwise they come out all wrong.

Cheers,
Smithy.
Old 04-16-2010, 05:38 PM
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Default RE: 1/4 scale

1527 degrees (celcius) = SMOKIN' !!!
Old 05-25-2010, 12:22 AM
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Default RE: 1/4 scale

Hey Guy's,

Here's a little video for you, it's only an engine test run but will give you an idea at least.

http://www.youtube.com/watch?v=Lu-UC5afVIM

Enjoy.

Cheers,
Smithy.
Old 08-14-2010, 02:07 AM
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knobby1
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Default RE: 1/4 scale

Hey All,

Had a chance for a quick launch test @ ~80% yesterday, also tried the parachute, seemed to work pretty well....Enjoy.

http://www.youtube.com/watch?v=qk5-evHF1uA

Cheers,
Smithy.
Old 08-14-2010, 02:28 AM
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Default RE: 1/4 scale

that's great mate...how did you do the chute without it burning up???
Old 08-14-2010, 04:27 AM
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ORIGINAL: Mudgy

that's great mate...how did you do the chute without it burning up???
Hi Mud,

I have ~50cm of 40lb fishing tracer for the attachment so it wont burn/melt when it hits the A/B pipe, then it's connected to some nylon cord, then to the chute lines themselves, all up the chute is ~2.5m behind the car when it's extended. The container I use for it is just a stainless salt shaker with a spring loaded cup. When I hit the release servo the spring shoots the chute ~60cm out the back....works great.

Cheers,
Smithy.
Old 08-18-2010, 05:51 PM
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Default RE: 1/4 scale

WOOOSH!!!!
Awesome work mate.







Someone should design a 1/4 scale lightweight fire extinguisher that can be mounted on the car and operated via the radio in case of fire down the other end of the dragstrip.








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