RE: Rear motor mount question...

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gsanders

EastCoaster
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I need a little help.

My build instructions tell me to epoxy the forward motor mount centering ring in place (FG) and before that dries it tells me to temporarily insert the rear (aft) motor mount centering ring in place so the motor mount tube is centered in the body. Then it tells me to remove the rear (aft) centering ring after the forward ring epoxy has dried so I can then insert, align and epoxy-in the fins. Well... that all sounds just fine but how do you get the rear (aft) centering ring back out of the body? They are in there rather tight with a bit of a friction fit.

Does anyone have any tips and ideas? Thanks.
 
Wood? Put some drywall screws into it and yank it out after the glue dries. If not using klips, just flip the ring so the holes are on the inside.
Fiberglass? Use cellophane tape tabs to pull the ring back out. Be sure of your tabs. You can also use screws in the 'glass rings too.
 
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If it's too late for Adrian's advice, use a screw driver or some sort of long skinny rod, insert through the fin slots and tap the ring out.
 
I drill and tap the CR for a 4-40 threaded rod.

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I usually make tape 'tabs' to pull out my CRs. Wrap a piece of tape around the CR, thru the MMT hole. Repeat to make two, to have an even 'pull out'. A very thin cord will also do (like a length of thread or string)..
 
If it's too late for Adrian's advice, use a screw driver or some sort of long skinny rod, insert through the fin slots and tap the ring out.

When I found myself In that situation, I just used my fin tabs to back the ring out. Probably not the bet route, but it paid off at the time

Question though: Is this a slotted tube for fin tabs? If they're surface mounted, the slot push naturally won't work.
 
When I found myself In that situation, I just used my fin tabs to back the ring out. Probably not the bet route, but it paid off at the time

Question though: Is this a slotted tube for fin tabs? If they're surface mounted, the slot push naturally won't work.

I've done the same, just wasn't recommending it.:wink:

OP says "insert, align and epoxy-in the fins"..I took that for fin tabs.
 
I need a little help.

My build instructions tell me to epoxy the forward motor mount centering ring in place (FG) and before that dries it tells me to temporarily insert the rear (aft) motor mount centering ring in place so the motor mount tube is centered in the body.

Do what everyone has already recommended: pre-insert tape, string, floss, or some other thread on which you can pull to get the rear centering ring (CR) out. If all else fails, tap a hole, or use a wood screw to attach it to the CR to remove it.

Banging it out with a fin could also work, but implies that the fin slots extend far enough to the edge of the airframe to impact on the rear CR.

Then it tells me to remove the rear (aft) centering ring after the forward ring epoxy has dried so I can then insert, align and epoxy-in the fins.

One word of caution - the above instructions imply that the one an only attachment point (FWD centering ring) will be sufficient to maintain perfect latitudinal alignment of the motor mount (MMT). If there are 2 forward CRs - sure. If not, you run the risk of moving the CR while you epoxy your fins. If that happens, the rear CR will not fit, and even if you make it fit, the rocket will never fly straight.

I try to keep the rear CR still in place, perhaps moved to the very edge of the airframe, but still in place, while epoxying the fins. This ensures perfect MMT alignment.
After the fins are epoxied, THEN I pull out the rear CR for internal fillets. If desired.

YMMV,
a
 
I tend to glue the forward CR to the MMT. I then prep the rear CR for easy removal (see above). I will then glue the forward CR / MMT assembly into the tube, with the rear CR in place to ensure alignment. It's also far enough away from the fin attachment area to ensure it doesn't get glued in place. (I've obviously ensure the fins fit & and have done a 'dry fit'.) I then insert the fins & glue them in place. Sometimes I'll remove the rear CR to ensure that there is no glue in the path / placement of the rear CR, then re-assemble until the fins are fully cured in place. Remove the rear CR, and add internal fillets, blocks for buttons, etc.. then glue in the rear CR

The rear CR, until placed & glued, tends to be flush with the rear of the BT to ensure it is easy to remove & won't get glued in place. I have, once or twice, had to scrape a bit of glue off the inside face of the BT to get the rearward CR back in place.
 
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