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  #1  
Old 04-21-2020, 02:40 PM
RobVG RobVG is offline
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Default D12-3 vs D12-5 max lift weight ?

Thought I was starting to understand engines until I read the Estes chart.

It looks like all the specs are same between the 2 engines except for delay and initial weight - 1.49g vs 1.52g.

Max lift wt for the -3 = 396g. -5 = 283g

What am I missing?
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  #2  
Old 04-21-2020, 02:50 PM
joltinjoecanada joltinjoecanada is offline
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The 5 second delay engine will lift the heavier rocket but the delay will be too long. The 3 second delay engine will lift the lighter rocket, but the delay will be too short. Anyway, that's my read on it, but I've been wrong before.
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Old 04-21-2020, 05:14 PM
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Earl Earl is offline
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Both engines will lift the same because thrust and power-wise, they ARE the same. However, heavier weight rockets, obviously, will not coast as long, so the 3 second delay is more appropriate. Lighter weight rockets will coast longer with that same amount of power, so they will need the longer delay.

So, for a GIVEN engine ‘type’ (A8, B6, C6, D12, etc.), the variations in rocket weight (all other things equal) are what determines which DELAY to use for that rocket. Something like a small Alpha might use the A8-5, whereas the larger Big Bertha will definitely need the A8-3. In either case, the A8 motor will be producing the same exact amount of thrust for each flight.

I hope that helps.

Earl
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Old 04-21-2020, 08:28 PM
RobVG RobVG is offline
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Both answers help.

Maybe I don't understand the terminology.

I assumed "Max lift weight" meant the heaviest rocket it could lift?

Estes Engine Chart
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  #5  
Old 04-21-2020, 08:40 PM
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Earl Earl is offline
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Quote:
Originally Posted by RobVG
Both answers help.

Maybe I don't understand the terminology.

I assumed "Max lift weight" meant the heaviest rocket it could lift?

Estes Engine Chart


I suppose what they mean by “max lift weight” is actually something closer to “max lift weight AND safely eject a recovery system BEFORE impacting the ground”.

Earl
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  #6  
Old 04-21-2020, 08:53 PM
RobVG RobVG is offline
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Quote:
Originally Posted by Earl
I suppose what they mean by “max lift weight” is actually something closer to “max lift weight AND safely eject a recovery system BEFORE impacting the ground”


That makes sense.

Thanks Earl
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