#1
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How to repair engine mounting system in Big Bertha
Hi all,
I'm a VERY casual builder and claim no expertise. My engine mount in my Big Bertha was damaged and needs to be replaced. I managed to get the unit out, but I don't know how to replace it. Does Estes sell replacement parts like that? Also, I can't quite remember the build. I'm assuming I just put glue on the cardboard washer things and position the unit in place to dry in the body tube. Is that right...? Thanks! |
#2
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Sand as much of the old glue and cardboard from inside the tube as possible, then rebuild the mount and slide it in. This would be a good time to upgrade the recovery system if you have a mind to with Kevlar. The parts should be easy to find. Two CR-2060 rings, an 18mm engine hook, a 520 engine block and a length of BT-20 would be all you need. As for length on the BT-20, the normal 2.75" length should work fine, but some opt for a longer piece of BT-20 to fill a little more of the Bertha body tube to make it easier for the ejection charge to push out the recovery system. Check Semroc for the parts. If you want to go the Kevlar route, PM me with your address and I'll sent you a yard. I have a "little" extra.
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Bill Eichelberger NAR 79563 http://wallyum.blogspot.com/ I miss being SAM 0058 Build floor: Centuri Mini Dactyl Estes - Low Boom SST Semroc - Marauder, Shrike, SST Shuttle In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Multi-Roc, Solar Sailer II Semroc Cyber III Ready to fly: Estes - Solar Sailer II Semroc - Earmark, Groonie Der V 1/2 |
#3
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Quote:
With that, you can fly some D motors, and maybe some E's. But it goes way up there on a D12, and about out of sight on E's, so take some young eyes with you to the rocket range Doug .
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YORF member #11 |
#4
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Not to rain on the parade,
Didn't the older/original Big Berthas have an engine mount that included a coupler between the centering rings? If you look inside and see a short length (about 2") of black phenolic or unsealed paper tubing, then you may have to go a different route replacing the engine mount. If you have such a piece in there, then I'd use a longer stuffer tube and preglue the top centering ring in place (with some kevlar like Bill suggested) and then slide this down from the top of the body tube to meet the lower centering ring glued in place at the bottom. It might be a little tricky but doable.
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NAR 79743 NARTrek Silver I miss being SAM 062 Awaiting First Launch: Too numerous to count Finishing: Zooch Saturn V; Alway/Nau BioArcas; Estes Expedition; TLP Standard Repair/Rescue: Cherokee-D (2); Centuri Nike-Smoke; MX-774 On the Bench: 2650; Dream Stage: 1/39.37 R-7 |
#5
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Quote:
A Mini-Broadsword.
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Scott D. Hansen Ye Olde Rocket Shoppe - Your One Stop BAR Shoppe! Ye Olde Rocket Plans - OOP Rocket Plans From 38 Companies! Ye Olde Rocket Forum WOOSH NAR Section #558 |
#6
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Wow! you're really going way back! for many years the Big bertha mount has been a BT-20B(8 5/8") and 2 centering rings, with a motor hook. I recall buying a Big Bertha starter set around 1990 and it having that set-up. I believe the coupler disappeared sometime circa 1980's.
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Jeffrey Deem NAR16741 CIA section 527 |
#7
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Here's what I bought then: http://www.spacemodeling.org/JimZ/estes/est1948.pdf
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Jeffrey Deem NAR16741 CIA section 527 |
#8
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Yes, Yes . . . I go waaay back . . . I know, I know. . . I'm old.
Trust me, I know.
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NAR 79743 NARTrek Silver I miss being SAM 062 Awaiting First Launch: Too numerous to count Finishing: Zooch Saturn V; Alway/Nau BioArcas; Estes Expedition; TLP Standard Repair/Rescue: Cherokee-D (2); Centuri Nike-Smoke; MX-774 On the Bench: 2650; Dream Stage: 1/39.37 R-7 |
#9
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LOL I was thinking like you do, Mark... Guess my age is showing... Later! OL JR
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The X-87B Cruise Basselope-- THE Ultimate Weapon in the arsenal of Homeland Security and only $52 million per round! |
#10
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I believe it changed in the mid 70's from the coupler style to the current style. The coupler style mount remained popular in several Centuri kits until the end.
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I love sanding. |
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