Big Daddy quandry

[Rural]

While on vacation, I made a point to poke my head in every hobby shop we passed in a mall. (My wife's idea of a vacation involves lots of malls.) My son (5) and I have two rockets under construction, so we were not looking for another kit, but I was ready to make an exception for the Estes Big Daddy. As luck would have it, I found one and snapped it up.

This is our first kit that accepts mid-power motors so we paid special attention to the construction details of the motor-mount before putting it together. As it went together, with glue in place, I noticed that the top of the motor hook pierces the motor-mount tube well below the engine block ring. So I figured there was no harm in pushing the ring down so that it butted up against the top of the hook. This is how it is displayed in the construction diagrams.

With the change made and glue dry, I started wondering if I had made a mistake. This kind of second-guessing is normal for me. So I used a ruler and a pencil to determine what length of motor this will allow. A 100 mm engine would be perfect. With an Estes E-motor, or a D with the E-to-D spacer, I'd have 5 mm of wiggle room. My fears were addressed, but that 5 mm gap bothered me.

Would Estes purposefully design for 5 mm of gap? Why? If I build another Big Daddy, could I safely reduce the gap for a tighter fit?

 

[Handeman]

I don't have a Big Daddy, but 5mm is about a 1/4" and seems like too much slop.
First question, have you actually installed an E and D with spacer?

5mm also sounds like the height of the thrust ring. Are you sure the hook wasn't supposed to go on the top of the ring and eliminate the slop?

You really want the hook to hold the motor in place without much end to end slop. You can always use a longer spacer for a D motor and a shorter one for an E if worse comes to worse. Just cut a used motor to length.

 

[dcastle]

Normally the engine block goes above the hook, butting right up against it. It sounds like you did it just right; Estes never had a kit design to my knowledge that requires the ring to sit below the top of the hook. It functions as a backup, of sorts, to the top of the hook and prevents the motor thrust from pushing the hook thru the motor mount.

I wouldn't worry much about a little wiggle room as you describe. if the motor is a little loose, it will move forward against the ring while thrusting and be caught by the bottom of the motor hook upon ejection. If you want to add a little masking tape around the motor to friction fit it and prevent some of that movement, it wouldn't be a bad idea plus it would add some additional seal to avoid ejection gas leaks. You can also add some masking tape around the motor end and the bottom of the hook to provide some protection against the motor being ejected.

I think you are fine, over all, from what you are describing.

 

[jadebox]

While on vacation, I made a point to poke my head in every hobby shop we passed in a mall. (My wife's idea of a vacation involves lots of malls.) My son (5) and I have two rockets under construction, so we were not looking for another kit, but I was ready to make an exception for the Estes Big Daddy. As luck would have it, I found one and snapped it up.

This is our first kit that accepts mid-power motors so we paid special attention to the construction details of the motor-mount before putting it together. As it went together, with glue in place, I noticed that the top of the motor hook pierces the motor-mount tube well below the engine block ring. So I figured there was no harm in pushing the ring down so that it butted up against the top of the hook. This is how it is displayed in the construction diagrams.

With the change made and glue dry, I started wondering if I had made a mistake. This kind of second-guessing is normal for me. So I used a ruler and a pencil to determine what length of motor this will allow. A 100 mm engine would be perfect. With an Estes E-motor, or a D with the E-to-D spacer, I'd have 5 mm of wiggle room. My fears were addressed, but that 5 mm gap bothered me.

Would Estes purposefully design for 5 mm of gap? Why? If I build another Big Daddy, could I safely reduce the gap for a tighter fit?

The engine hooks are just a hair longer than the motors. The Big Daddy's engine hook fits an E motor, so I don't see how you can really have the gap you indicate.

The engine hook should be 3.75" (or 95 mm) long which is the length of an E motor. If it's longer, then it wasn't you who made a mistake.

Edit: On second thought ... the Estes-style engine hooks have that curly-Q end to make it easier to insert a motor. Your hook may have gotten straightened out a little too much. You might have to bend in the end that touches the bottom of the motor a little.

-- Roger

 

[hardinlw]

Typical Estes construction is to have the engine block on top of the hook just like you describe doing it. I've never seen it leave as big a gap as you say you have. If you fly a D engine or (hint, hint) one of the Aerotech reloadables, you need a spacer which probably came in the kit. If not, use a piece of BT-50 coupler. One upgrade I would suggest based on a failure mode we observed in a TARC rocket is to install a couple on top of the engine block to double up the part of the motor tube ahead of the engine. We actually had the motor tube burn through from the ejection charges in the Aerotech reloadables which apparently are more energetic than those in the Estes engines. The couples are harder and offer quite a bit more protection from the heat of the ejection charge.

 

[gpoehlein]

I discovered the hard way at our last launch - if you use an Aerotech reloadable E, replace the chute with something a bit sturdier than the stock plastic chute. Five of the six shroud lines seperated from the chute on me. (The plastic chute works fine with Estes E9 motors.)

 

[ttabbal]

I discovered the hard way at our last launch - if you use an Aerotech reloadable E, replace the chute with something a bit sturdier than the stock plastic chute. Five of the six shroud lines seperated from the chute on me. (The plastic chute works fine with Estes E9 motors.)

I've started purchasing a few nylon chutes that I just swap between rockets. Stronger and usually easier to pack, the only exception being the really narrow body tubes. It helps if you use a snap swivel to attach the chute so you can easily move it between rockets. I also prefer to tie a loop in the shock cord to attach the chute. The nose cones just break too easy for my taste. I also prefer thin kevlar line for the shock cord, just use a lot of it so you don't get too hard a jolt at deployment.

 

[Sailorbill]

Typical Estes construction is to have the engine block on top of the hook just like you describe doing it. I've never seen it leave as big a gap as you say you have. If you fly a D engine or (hint, hint) one of the Aerotech reloadables, you need a spacer which probably came in the kit. If not, use a piece of BT-50 coupler. One upgrade I would suggest based on a failure mode we observed in a TARC rocket is to install a couple on top of the engine block to double up the part of the motor tube ahead of the engine. We actually had the motor tube burn through from the ejection charges in the Aerotech reloadables which apparently are more energetic than those in the Estes engines. The couples are harder and offer quite a bit more protection from the heat of the ejection charge.

Larry why would you need a spacer for the AT 24/40 reloadable motor? Reloadable motor has a thrust ring on it making the forward part of the Hook and the motor block unnecessary. I think I have heard that the motor hook can interfere with the forward closure.
If you use the Estes motor hook for retention it is a good idea to run tape or a tye wrap around the motor and the hook, It really creats a vacuum to loose a motor case.

 

[G2Rockets]

Bill,
He could always upscale his motor tube like the one we saw at thor in June. Did you see the bad daddy. If I remember correctly it had a 54mm in it:y:. I still wonder how that will ever be found after launch. was it you or Rich that had the modified Big Daddy?

take care
John

 

[hardinlw]

The reason for using a spacer ahead of the 24/40 reloadable casing is that the Estes motor mount tube tends to fray a bit after repeated flights with an F39 (my favorite reload for this case). Inserting the space so that the thrust load is primarily carried by the thrust ring improves my peace of mind. The standard Estes hook does interfer with the forward closure on the 24/40. It was no fun filing it down after it was installed, so now I remember to nip it before installation. I believe the new Big Daddy kits accept an E engine which is longer and thus the forward end of the hook ends up ahead of the closure.