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Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 5:47 pm
by juicedcoupe
Frankentruck wrote: ↑Fri Apr 21, 2023 5:38 pm
Don't the rocket motors shoot a charge out the front once they burn to the end?
It depends on if they are designed to discharge a parachute or to be used in stages.
Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 5:50 pm
by Frankentruck
Does that matter? If in stages, I thought the discharge from the bottom one then ignites the next motor about it. I've only launched single stage rockets though.
Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 6:02 pm
by coxbros1
Frankentruck wrote: ↑Fri Apr 21, 2023 5:38 pm
Don't the rocket motors shoot a charge out the front once they burn to the end?
The rockets with a "0" at the end (ie. F15-0) have no discharge for chutes..the rockets I am using are all single stage rockets with no discharge...basically the only question is how fast is it gonna run, can I drive it, and will it stop!...I am going with a 24" parachute
Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 7:07 pm
by GoMachV
On the old rocket car I had they ran a couple brass elbows off the front so they could stuff a parachute in it. I doubt it worked well, but it sure looked funny

Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 7:17 pm
by juicedcoupe
coxbros1 wrote: ↑Fri Apr 21, 2023 6:02 pm
will it stop!...I am going with a 24" parachute
Since you are using a solid rear axle, can you use some type of disk brake. Maybe attach the disk in place of a spur gear or something.
Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 7:22 pm
by coxbros1
juicedcoupe wrote: ↑Fri Apr 21, 2023 7:17 pm
coxbros1 wrote: ↑Fri Apr 21, 2023 6:02 pm
will it stop!...I am going with a 24" parachute
Since you are using a solid rear axle, can you use some type of disk brake. Maybe attach the disk in place of a spur gear or something.
Yes...and I seriously thought about that...and might do it later...but for now, I will use a chute...just purchased it!....24" ..$59 otd!
Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 8:02 pm
by RC10th
Looking good, I'm curious to see how this transpires with a more modern and well thought out design.
I've never seen colored engine adaptors.
My car used the ejection charge to deploy the chute by grabbing a clip upon ithe engines departure from the car.
Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 8:41 pm
by coxbros1
RC10th wrote: ↑Fri Apr 21, 2023 8:02 pm
Looking good, I'm curious to see how this transpires with a more modern and well thought out design.
I've never seen colored engine adaptors.
My car used the ejection charge to deploy the chute by grabbing a clip upon ithe engines departure from the car.
Those colored adapters just allow using smaller engines where the big one go...I will start with two "D" engines and work my way up...might end up with one "F"....just have to see how it works out
Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 9:35 pm
by GoMachV
wrote:
I will start with two "D" engines...
Hard to go wrong with double D's
Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 9:41 pm
by juicedcoupe
coxbros1 wrote: ↑Fri Apr 21, 2023 8:41 pm
might end up with one "F"....
You can bet that it'll end up with one giant
"F"
Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 9:42 pm
by RogueIV
Speaking as a village idiot that launched a model rocket horizontally once, you're definitely going to want brakes.
Also you might want to move the rockets back a little bit so you're not turning your axle into a rotisserie, those things burn pretty hot and it may warp/damage the axle
Re: Old School Rocket Car Build
Posted: Fri Apr 21, 2023 11:40 pm
by RC10th
We only had cardboard tubes and rings as engine adaptors.
That looks like a good chassis for a rocket car. Looks like a Pro Stock and a Legends kit had a baby

I'm sure it would be easy enough to get Jeff to make rocket specific side plates with holes to experiment with rocket placement and thrust angles. I actually like the way your rockets appear to provide some downforce in front of the rear tires. I feel this would likely also allow you to run some bigger engines while maintaining good stability.
According to the Estes engine chart the D engines actually provide quite a bit more thrust at 7.4lbs than the E engines at 5.6lbs, but the E engines burn 1.2 seconds longer.
I'd be curious what your car weighs compared to your calculations, just for interest sake mine is 648 grams ready to run minus receiver, which I could still reduce some weight if I wanted to.
Re: Old School Rocket Car Build
Posted: Sat Apr 22, 2023 5:15 am
by Elkcycles
I'm curious how your charge timing will work out with two parallel motors. Will you be launching with on board ignition or a conventional starter?
Additionally, it looks like you could cut an eccentric slot at the front motor mount bolt, so that you could angle the mount up or down to experiment with motor positioning.
Re: Old School Rocket Car Build
Posted: Sat Apr 22, 2023 7:36 am
by coxbros1
RogueIV wrote: ↑Fri Apr 21, 2023 9:42 pm
Speaking as a village idiot that launched a model rocket horizontally once, you're definitely going to want brakes.
Also you might want to move the rockets back a little bit so you're not turning your axle into a rotisserie, those things burn pretty hot and it may warp/damage the axle
They angle above the axle pushing the car downwards
Re: Old School Rocket Car Build
Posted: Sat Apr 22, 2023 7:38 am
by coxbros1
Elkcycles wrote: ↑Sat Apr 22, 2023 5:15 am
I'm curious how your charge timing will work out with two parallel motors. Will you be launching with on board ignition or a conventional starter?
Additionally, it looks like you could cut an eccentric slot at the front motor mount bolt, so that you could angle the mount up or down to experiment with motor positioning.Screenshot_20230422-051557_Samsung Internet.jpg
Yup, that's the plan...I have a way of igniting them simultaneously....I think
