A Rocket That Launches Attached To A Horizontal Track That Transitions To Vertical

[manixFan]

Once upon a time long ago I saw this tried. When the rocket hit the bend it simply ripped off the guides and kept going straight. Pretty much as soon as it hit the curve. The idea to use a low thrust 'starter' motor and then stage to a more powerful one sounds reasonable, but you can imagine all kinds of things that could go wrong.

Another big issue is the amount of wasted energy, as Steve points out, lots of thrust used to go nowhere.


Tony

 

[boatgeek]

This ^^^

Quote of the year:

boatgeek 2020-02-25: ... "in theory there’s no difference between theory and practice."​

I wish I could claim that as my own, but it came to me from a college friend who did her PhD in CS theory. I use it often though!

 

[boatgeek]

The more I think about this, the more I think that you don’t want the sled to ride on balls in the track—you want it to ride on wheels on a T or I shaped track. You lose a lot less energy to friction that way. Rollerblade or skateboard wheels are pretty cheap and have pretty good bearings. Two axles should be good to prevent binding, and you’ll need a way to keep the web from buckling as you bend it.

 

[lakeroadster]

So here are conceptual drawings I just finished today. Just trying to get some stuff down for everybody to look at to get ideas flowing.

Think slot cars when you look at these.... but two pins down from the car engaging into the track, one at each of the axle c/l's.

Also.. think Hot Wheels cars and tracks.

I initially didn't have the lower wheels, but without them I'm thinking the internal rail on the car and the thrust of the rocket will try to raise the rear end of the car at the transition form straight to upright, which would cause the rear pin to lift up and gouge into the track. Basically similar (kinda sorta) to what's used on a roller coaster.

I started with a short car... then stretched it out. I show the car as a solid piece, but I could make it from 1/4" or 3/16" brake line tubing. But it looks kind of "32 Ford'ish"... or like an old Oliver Tractor... and hey... looks matter.

Speaking of tractor... I could make the sled a tractor motor configuration... with two canted motors up front...

I just tossed my "Hammered Head Shark" rocket on for reference. I'd like to make the car a multi-purpose / multi rocket configuration.

I'm in a design frenzy... .... time to walk away... for now.

 

[Daddyisabar]

ME 163. A Hanna Reitsch special edition!

 

[jqavins]

With a sled on top you want the wheels, lugs, or whatever you use to be as far apart as you can get them, as you've shown. If you go with the rocket (with or without a carrier) on the bottom then you want the supports as close together as practical.

The "rod" could be a hollow tube with a slit on 1 side facing down. The guides on the rocket could be similar to rail buttons but more of a sphere on the end of a shaft. Keep the shaft longer to allow for the curve of the tube and the ends being spherical should ignore the curve.

I still like this option, with the balls made of a low friction material like Delrin®.

Quote of the year:

boatgeek 2020-02-25: ... "in theory there’s no difference between theory and practice."​

I wish I could claim that as my own, but it came to me from a college friend who did her PhD in CS theory. I use it often though!

I'm afraid your friend didn't come up with it either. It's quite old, with multiple conflicting attributions if you Google it. And it's abbreviated; the whole thing is "In theory there's no difference between theory and practice, but in practice there is." It's one of my favorites, and one of the things I sometimes use as a sig. (Which is why I know about the attributions; I always give attributions for my sigs when I can.)

 

[Greg Furtman]

The classic example is

Liftoff is about 2 minutes in.

I remember watching this as a kid in the movie theater.

 

[Greg Furtman]

So here are conceptual drawings I just finished today. Just trying to get some stuff down for everybody to look at to get ideas flowing.

Think slot cars when you look at these.... but two pins down from the car engaging into the track, one at each of the axle c/l's.

Also.. think Hot Wheels cars and tracks.

I initially didn't have the lower wheels, but without them I'm thinking the internal rail on the car and the thrust of the rocket will try to raise the rear end of the car at the transition form straight to upright, which would cause the rear pin to lift up and gouge into the track. Basically similar (kinda sorta) to what's used on a roller coaster.

I started with a short car... then stretched it out. I show the car as a solid piece, but I could make it from 1/4" or 3/16" brake line tubing. But it looks kind of "32 Ford'ish"... or like an old Oliver Tractor... and hey... looks matter.

Speaking of tractor... I could make the sled a tractor motor configuration... with two canted motors up front...

I just tossed my "Hammered Head Shark" rocket on for reference. I'd like to make the car a multi-purpose / multi rocket configuration.

I'm in a design frenzy... .... time to walk away... for now.

View attachment 407484 View attachment 407485 View attachment 407486 View attachment 407487 View attachment 407488

This looks good but the curve needs a larger radius & according to the rules you would only need 70 degrees & not 90.

 

[Alan R]

be sure your rocket looks like this one... (just skip to :40)...


my favorite toy when I was 7 btw

 

[BABAR]

For the folks saying "It doesn't seem worth it" and "why" ... the worth it part is to do something different. But then again I've always been like that.

Think of the visual.. and rocket sitting visual on a long track... the engine(s) fire and it hauls butt down the track, slides up the radius, off the track and up into the sky. You could even build it as a 2 stage so it stages while on the track... where the booster stage is heavy so it lumbers along until the second stage fires, at which point the acceleration seems incredible due to the light weight of the second stage. It could even be on a cart, where the cart falls away at the end of the ramp.

44 years ago I actually built a rocket with a track when I was in High School, but never launched it. The base was made from a 2x4 with a routed slot in the center. (Just a flat 2x4 about 6 ft long). It had two cover plates that were nailed to the top of the base. The rocket had (2) inverted T-Shaped metal hooks that hung underneath, one in the nose cone and one near the motor mount.

The rocket had a hinged door in the body tube so the chute would pop out the top.

View attachment 407441
________________________________________________________________________________________________
The same track could be easily made, then notches added to create the curve.

View attachment 407442

Wish this would show your picture/diagram, but can't bring it through on this computer.

Any two fixed attachment points are likely to bind on a curved rail or track. Launch lugs on rails, buttons in slots, whatever.

Wheels would be great, but don't provide "adhesion" to the track (you don't want this puppy coming off the track prematurely.)

Combo would work. Single rail button in the "slot" as on your track. This give you "adhesion" for safety purposed, but as a single point of contact doesn't bind. three or four wheel "cart" (3 wheels means less energy spent "spinning up" the wheels) runs the rocket the length of the track and easily handles the curve. You can have a rubber stop at the vertical end of the track to stop the cart at which point rocket separates.

For bonus points, add elastic bands from the front of the cart to notches on the back of the rocket fins, with a release trigger for the rocket at the end of the track (cart hits rubber stop, fires trigger, releases rocket, bands yank the rocket forward.) You can impart some extra momentum to the rocket as it leaves the cart.

Cool project. On a full scale, might be a practical method for "rail gun" launching of rockets (use electromagnetic or other means of getting the sled up to speed at the vertical end of the track.) On a model scale, definitely far less efficient than just launching straight up a rod, as you are going to lose a lot of your black powder accelerating the cart and overcoming drag on your wheels and button/slot friction.

 

[Cape Byron]

be sure your rocket looks like this one... (just skip to :40)...


my favorite toy when I was 7 btw

Exactly what I was thinking, Alan R!

 

[lakeroadster]

I did some searching online and found some wheels for 3D printing. Armed with that data... here are some more drawings for your review, input, thoughts......

See Post 152, here's a link: https://www.rocketryforum.com/threa...itions-to-vertical.157861/page-6#post-1972018

 

[Alan R]

here are some more drawings for your review, input, thoughts......

Realized while looking at @lakeroadster 's post (good stuff btw) that the problem here is the angle of the curve. You could do a 120-degree angle instead of 90, it would have almost the same visual effect, but it would be less inclined to binding (per @BABAR )

 

[Greg Furtman]

Realized while looking at @lakeroadster 's post (good stuff btw) that the problem here is the angle of the curve. You could do a 120-degree angle instead of 90, it would have almost the same visual effect, but it would be less inclined to binding (per @BABAR )

I agree. I think that120 degrees would make things easier and preformance better than a full 90 degrees.

 

[lakeroadster]

Realized while looking at @lakeroadster 's post (good stuff btw) that the problem here is the angle of the curve. You could do a 120-degree angle instead of 90, it would have almost the same visual effect, but it would be less inclined to binding (per @BABAR )

I agree. I think that120 degrees would make things easier and preformance better than a full 90 degrees.

You fella's mean 60 degrees of curve, not 120, right? 120 means the rocket arc's back toward you if you're standing near the starting line.

Binding isn't an issue... unless the design is incorrect. The idea is for the rocket to launch nearly vertical.

I'll concede the more angle the sled has to "climb" the more speed that will be scrubbed off, and that a bigger radii is better than a smaller radii.

At the launch site I can always raise the starting line (sawhorse) and lower the curve, which effectively gives the sled a running start. That's how most of the sci-fi sleds were presented over the decades.

 

[neil_w]

I think they meant something like this (add curves as necessary):

 

[Alan R]

You fella's mean 60 degrees of curve, not 120, right?

I mean an obtuse angle greater than 90 from one end of the rail to the other

 

[jqavins]

I think they meant something like this (add curves as necessary):
View attachment 407647

That's a 60°turn. It starts out 30° up from horizontal and ends up 90° up, so Δθ = 60°.

 

[neil_w]

Yes, Δθ = 60°, but that is nonetheless what I believe was meant by 120° in the posts by Alan and Greg above.

 

[jqavins]

Yeah, I think that's what they meant. And as lakeroadster wrote "You fella's mean 60 degrees of curve, not 120, right?" he was right. The correct term would be "a 60° turn".

 

[boatgeek]

A couple of suggestions:
Instead of 3-D printed wheels, use nylon bushings as tires over ball bearings (or even just the bearing OD). YMMV on 3-D printing, but I've never seen a really nice smooth surface like you'll want for wheels. You want to minimize friction as much as possible.

The dual launch lug holding the rocket is going to be hard on both the rods and the lugs. I see the rods crunching up the tube at the bottom. If you use a fork that goes on either side of the nozzle to transmit thrust to the rocket, the lugs will only be carrying the guiding forces and won't be under as much load. You might also want to cut the lugs square and have them rest on a flat surface that the rod glues into rather than having bent rods. The bent rods look like they might bind to me.

Does the rocket motor light as a cluster with the sled motor? If so, do you have a sense of whether the rocket motor will still be burning at the end of the track?

 

[lakeroadster]

A couple of suggestions....

Thanks for the comments and suggestions. Much appreciated.

Keep in mind I'm frugal... some would say to a fault. The "low buck" mantra is a driving force...

Instead of 3-D printed wheels, use nylon bushings as tires over ball bearings (or even just the bearing OD). YMMV on 3-D printing, but I've never seen a really nice smooth surface like you'll want for wheels. You want to minimize friction as much as possible

The wheels are for use in a 3D printer, they are not 3D printed wheels ... I can get (12) of these wheels for under a buck a piece.

The track is made out of wood, multiple pieces cut to size on my 1940's DeWalt radial arm saw and then screwed together. I'll cover it with gloss spar urethane. End result should be pretty smooth surface, and very cost effective too.

The dual launch lug holding the rocket is going to be hard on both the rods and the lugs. I see the rods crunching up the tube at the bottom. If you use a fork that goes on either side of the nozzle to transmit thrust to the rocket, the lugs will only be carrying the guiding forces and won't be under as much load. You might also want to cut the lugs square and have them rest on a flat surface that the rod glues into rather than having bent rods. The bent rods look like they might bind to me.

Agreed. I was merely spit balling, trying to see how I could attach my nearly completed Hammerhead Shark to the sled.

I'll likely build a really simply rocket as the test mule, 3 fins to have a nice unobstructed "belly" for support. Then the body tube could be supported full length, and still use the dual launch lugs as the release mechanism.

Let's face it... if the rocket motor doesn't light, the 2 lb (guesstimates) sled is going to pulverize it when they tumble together off the end of the ramp and eventually are introduced to Mother Earth.

Maybe a rocket like this, but no wheels and 3 fins.. I could have Wiley riding on the sled too

Does the rocket motor light as a cluster with the sled motor? If so, do you have a sense of whether the rocket motor will still be burning at the end of the track?

That may indeed work but my gut tells me it will result in way too much speed, way too soon. But without some test firing of the sled who knows.

What I'm envisioning is a small battery pack on the sled and a switch that activates mechanically to fire the rocket motor (and perhaps fire more motors on the sled). Just a toggle switch that is flipped by a pin installed into the track.

I'll need to do a series of test fires of just the sled with some dead weight to simulate the rocket to get a feel for how fast the sled needs to go. Speed of the sled being adjusted by trying different rocket motors. Even if it takes a cluster at the back of the sled -or- a canted tractor motor cluster at the front of the sled -or- a multi stage configuration.. at this point it's an unknown. I do know that the more smoke the better, and getting everything tuned in is a big part of the fun!

Once the sled speed is dialed in then I'll have an idea where to locate the actuator on the track to fire the rocket motor.

IMO a sled rumbling down the track slowly.... then the rocket firing and things speeding up dramatically.... lets say right after the transition of the track from flat to curved ... would be visually impressive and would help to minimize G forces on the sled and rocket.

The testing phase should be a lot of fun...

Addendum..
I've also thought about having the sled snag a rather large parachute just as it exits the track. That would also look pretty cool and serve as a soft recovery for the sled on a "normal" run.... or the sled and the rocket in the event the rocket motor doesn't fire.

 

[boatgeek]

Thanks for the comments and suggestions. Much appreciated.

Keep in mind I'm frugal... some would say to a fault. The "low buck" mantra is a driving force...



The wheels are for use in a 3D printer, they are not 3D printed wheels ... I can get (12) of these wheels for under a buck a piece.

The track is made out of wood, multiple pieces cut to size on my 1940's DeWalt radial arm saw and then screwed together. I'll cover it with gloss spar urethane. End result should be pretty smooth surface, and very cost effective too.

View attachment 407652


Agreed. I was merely spit balling, trying to see how I could attach my nearly completed Hammerhead Shark to the sled.

I'll likely build a really simply rocket as the test mule, 3 fins to have a nice unobstructed "belly" for support. Then the body tube could be supported full length, and still use the dual launch lugs as the release mechanism.

Let's face it... if the rocket motor doesn't light, the 2 lb (guesstimates) sled is going to pulverize it when they tumble together off the end of the ramp and eventually are introduced to Mother Earth.

Maybe a rocket like this, but no wheels and 3 fins.. I could have Wiley riding on the sled too

View attachment 407656



That may indeed work but my gut tells me it will result in way too much speed, way too soon. But without some test firing of the sled who knows.

What I'm envisioning is a small battery pack on the sled and a switch that activates mechanically to fire the rocket motor (and perhaps fire more motors on the sled). Just a toggle switch that is flipped by a pin installed into the track.

I'll need to do a series of test fires of just the sled with some dead weight to simulate the rocket to get a feel for how fast the sled needs to go. Speed of the sled being adjusted by trying different rocket motors. Even if it takes a cluster at the back of the sled -or- a canted tractor motor cluster at the front of the sled -or- a multi stage configuration.. at this point it's an unknown. I do know that the more smoke the better, and getting everything tuned in is a big part of the fun!

Once the sled speed is dialed in then I'll have an idea where to locate the actuator on the track to fire the rocket motor.

IMO a sled rumbling down the track slowly.... then the rocket firing and things speeding up dramatically.... lets say right after the transition of the track from flat to curved ... would be visually impressive and would help to minimize G forces on the sled and rocket.

The testing phase should be a lot of fun...

Addendum..
I've also thought about having the sled snag a rather large parachute just as it exits the track. That would also look pretty cool and serve as a soft recovery for the sled on a "normal" run.... or the sled and the rocket in the event the rocket motor doesn't fire.

3-D printer wheels (as opposed to printed) make more sense. I think having the sled trigger a switch is far more likely to be seen as a rules violation because you can't turn it off. It's sort of like a fuse in that way. However, I believe that NFPA says that the rocket needs to lift off within 3 seconds of the button being pushed. You should be well within that timeframe, particularly if you use BP or CTI motor(s) on the sled.

If you want lots of smoke, three CTI 24mm F79s are your ticket. Canted motors port and starboard and a centerline one in the back. That's an investment in motors can casings, but it'd sure be fun. Hooking a chute off the ground is an interesting recovery method. I think you'd want it to be fairly small to limit shock loads, and maybe an X-form for maximum dragster look. If your sled really weighs 2 lbs, you won't want that to come down on tumble only.

 

[Joekeyo]

it looks like it was launched with a match-lit fuse (I may be wrong there, and not to say I haven't done it...)

Ditto.

 

[Joekeyo]

Use a square rocket. It will be easier to interface with the sled.

 

[BABAR]

Regarding parachute on sled, rethink.

Sled is at rocket launch velocity (presumably equivalent to “end of rod speed”)

NOT a good time (or at least velocity) to deploy a chute.

I discovered this when I had a long gap two stage, the booster pulled a chute from a pod off the sustainer at separation. Seemed like a good idea. Didn’t think about the fact that booster was at full velocity at the time. Chute shredded.

Might work with a long elastic shock cord.

 

[BABAR]

I agree. I think that120 degrees would make things easier and preformance better than a full 90 degrees.

At the point you aren’t doing 90, you kind of MISS the whole point. Why not 130? 140? Eventually you are at 180 (or zero, depending on your perspective) with a straight track.

Seems like the point is to convert horizontal to vertical velocity.

 

[lakeroadster]

Regarding parachute on sled, rethink.

Sled is at rocket launch velocity (presumably equivalent to “end of rod speed”)

NOT a good time (or at least velocity) to deploy a chute.

I discovered this when I had a long gap two stage, the booster pulled a chute from a pod off the sustainer at separation. Seemed like a good idea. Didn’t think about the fact that booster was at full velocity at the time. Chute shredded.

Might work with a long elastic shock cord.

Good point... maybe just a huge streamer then?

A streamer would give a neat visual and make finding it in the weeds easier. The streamer could be placed inside a piece of pvc tube attached to the curve of the track.

 

[jqavins]

At the point you aren’t doing 90, you kind of MISS the whole point. Why not 130? 140? Eventually you are at 180 (or zero, depending on your perspective) with a straight track.

Expanding on this, what really matters is not the total angle of the turn but rather the curvature. How many degrees or turn do you have over the length of the sled's wheelbase? 90° of curve just takes longer than 60°.

 

[beeblebrox]

All of you have missed one important point...It is not the angle that matters, a full 360° loop (From vertical back to vertical...) could work, the point of fact that has been missing is THE RADIUS of the curve. This would also be dependent on the size of the rocket. If for example the rocket was 18" long you probably would want a radius of at least 48"
Here is your example from the 1951 movie "When Worlds Collide" Build your rocket like this one... Note main motor ignites halfway down the track, the first part is actually on a downward angle...