Need Machining (lathe) Help

[slipstick]

I want to cut the knurls off an aft closure (Rouse-tech/aerotech type) so that it is the same diameter (flush) as the motor tube. Can someone do this for me? Two slots will have to be cut into the end (which I can do with a bandsaw or file) in order to use a spanner to tighten the closure, ,much like the larger Cesaroni closures.

[Warren B. MusselmanModerator]

This isn’t a problem Mike and I can easily accomodate you on this, however be aware that this makes the motor officially “uncertified” and while NCR usually doesn’t make an issue of these things other clubs may do so.

Warren

[Art HoagParticipant]

Warren is correct, by doing what you want to do with the closure then any motor using that closure is officially “modified” and is no longer a certified motor. Research launch only, NCR and TC have plenty of them. Those are TRA rules.

Art

[Anonymous]

I understand the sentiment here, and for my TRA records I never used modified closures. In fact, in retrospect, there were no “closures” as they were single use motors. I have flown tailcones on some other rockets.

That aside, I wonder… did Rouse certify tapped and untapped forward closures? Plugged vs. unplugged? (i.e. closures suitable for motor ejection). My guess is that Rouse, Dr. Rocket, etc. did NOT certify all closures. If they didn’t, then I don’t see why an aft closure that is smoothed down should be tossed out.

Along the same lines — If you fill the knurling with putty (so it is smoothed out and creates less drag) is it “modified”? I don’t know. It would be an interesting question of TRA.

[new2hprParticipant]

You might give Mr. Rouse a call. I thought I read something on TRF about him doing an aft closure with the OD matching the tubing, specifically for staged projects, but it didn’t go to market. I’ll try to find the thread.

Ken

[slipstick]

I contacted Tom Rouse and he said they make flush rear closures and they are currently in stock and do not affect the certifications.

I also contacted Robert DeHate at AMW about removing their aft thrust ring and that is OK as well.

So… the need for this thread no longer exists, other than as a reference for others that are wishing to do the same thing. I don’t need any special machining or exo-couplers at this time.

Thanks for everyone chiming in.

[Warren B. MusselmanModerator]

By the official rules, ANY modification of a motor casing or closures is forbidden. This means that the many flyers who have drilled and tapped plugged forward closures for eyebolts or who have had custom rear closures made or turned down from factory closures are essentially flying “illegally”.

If a manufacturer makes the part, it’s OK – if you make it, NOT OK. That said, no one is checking on such things and the rule is in place to make Tripoli’s and NAR’s insurance companies happy.

However, such things as custom rear-closure tailcones, while not a problem at NCR launches can be a big problem at other launches if the RSO is a stickler for the rules and if used in the context of a contest, might cause some grumbling from those flying without such an advantage. I would expect this to be a particular problem with NAR contests.

Again, all that said, I will gladly turn down the knurling on rear closures or center drill and tap plugged forward closures for eyebolts.

Warren

[Jeffrey Joe HintonModerator]

Happy to have helped out. Thanks Mike.

[AdrianParticipant]

I emailed Tom Rouse to see if I can get some flush aft closures in 38mm. They would be not only good as a sustainer coupler, but should help with base drag in altitude shots.

With a flush aft closure, it should also be possible to make a miminum diameter rocket with an integrated tailcone, into which the motor is loaded from the front. 🙂

[edwardModerator]

Instead of front loading, wouldn’t it be easier to turn down the retainer to a tailcone and then fly it on a research day?

Edward

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