Bullet Bobby 18 mm to 24mm?

[DirkTheDaring]

Has anybody put a 24 mm engine mount in the 18 mm Bullit Bobby? At 2.6 inches wide that sounds like a Bt 80, plenty of room, width-wise, but at only 7 inches tall, I dunno if there’s room for recovery, need for nose weight, etc.

At 20% off this weekend, if no one else has done it, I may try.

Thank you.

 

[mh9162013]

I think the primary concern will be the nose weight.

As for room for recovery, you can get 24mm engines that are the same length as standard 18mm engines. So if something works for 18mm, it should work for 24mm.

Also, don't forget you can sim what you have in mind.

 

[Pinetree]

I have three of them, and one is unbuilt.

A D motor would be interesting.

Perhaps a bit of Lead instead of clay in the nose would balance things out?

 

[DirkTheDaring]

I think the primary concern will be the nose weight.

As for room for recovery, you can get 24mm engines that are the same length as standard 18mm engines. So if something works for 18mm, it should work for 24mm.

Also, don't forget you can sim what you have in mind.

Certainly, but always good to see if there is a beaten path I can follow.

 

[Pinetree]

For that price, just send it.

 

[Blast it Tom!]

Or use an Aerotech 18mm D.

 

[Blast it Tom!]

Sorry, DP, what I'd like to see (and raise for your consideration) is a rear-eject conversion, so he comes back nose-down, like a proper bullet or bombshell! Has anyone tried that? (Not to hijack, I'll pull it if you'd like.)

 

[DirkTheDaring]

Sorry, DP, what I'd like to see (and raise for your consideration) is a rear-eject conversion, so he comes back nose-down, like a proper bullet or bombshell! Has anyone tried that? (Not to hijack, I'll pull it if you'd like.)

I have used rear ejection on other rockets, and I will certainly consider it if I proceed with Bobby Bullit

 

[SolarYellow]

24mm is in the works, and super easy even in the same form factor. Not overkill in the least lol, except when you put like a composite E30 in it. I have a full line of 24mm engines ready to test a production model soon!

Any updates?

 

[DirkTheDaring]

Has anybody put a 24 mm engine mount in the 18 mm Bullit Bobby? At 2.6 inches wide that sounds like a Bt 80, plenty of room, width-wise, but at only 7 inches tall, I dunno if there’s room for recovery, need for nose weight, etc.

At 20% off this weekend, if no one else has done it, I may try.

Thank you.

FWIW, I've placed an order for a 18 mm Bobby and I may even put a 29mm motor mount in it and the adapter down to 24 for first flights. But I'll run sims first.

 

[jhill9693]

It will require more nose weight, in addition to the nose weight already there. If you have a stock build, you could measure the loaded CG, then build your 24mm version and add weight until the CG matches.

That said, this is THE rocket to fly on Quest 18mm motors, especially the D20 and the C18. It flies very straight on these motors and it looks amazing going up! Here's mine on a D20:



Check out the mach diamonds!

The LCO remarked, "that's the straightest flight I've ever seen of a short fat rocket."

 

[jhill9693]

I am curious though to see what this would do on 24mm E motors, such as the Aerotech E30 or the Quest E35. So if you do it, I'd love to see how it goes.

 

[Blast it Tom!]

I am curious though to see what this would do on 24mm E motors, such as the Aerotech E30 or the Quest E35. So if you do it, I'd love to see how it goes.

If you  can see it! That boy would be a long way up!

 

[jhill9693]

If you  can see it! That boy would be a long way up!

Not as much as you would think. It's a high-drag design (remember drag increases with the square of the diameter), it's got a lot of base drag, AND it's going to have to have a lot more weight than say an Estes Fat Boy might, AND the motors I mentioned are short burners. All that factors into lower altitude.

You'd definitely want a big field, because the chute is coming out at apogee. Our club in SC has one. Speaking of which... the 24mm version might want a bigger (15" or 18") chute to prevent fin breakage.

 

[DirkTheDaring]

It will require more nose weight, in addition to the nose weight already there. If you have a stock build, you could measure the loaded CG, then build your 24mm version and add weight until the CG matches.

That said, this is THE rocket to fly on Quest 18mm motors, especially the D20 and the C18. It flies very straight on these motors and it looks amazing going up! Here's mine on a D20:

View attachment 634921

Check out the mach diamonds!

The LCO remarked, "that's the straightest flight I've ever seen of a short fat rocket."

Thank you!