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Looking through the 1974 parts catalog, it appears that the BT-65 is 1.796” in diameter. It is only listed in the balsa nose cone section.
I ordered some of the Semroc BT-65 clear tubing and it is too small for the Estes BT-65 nose cone and payload bay fitting. I tried heating the Semroc tubing but couldn’t get it over the Estes fittings.This info might help you,
https://www.keepandshare.com/doc10/29636/scrambler-instructions-ikv-34-pdf-940k?da=yhttps://www.erockets.biz/semroc-clear-plastic-body-tube-bt-65-5-0-long-sem-pst-65r/https://www.erockets.biz/semroc-clear-plastic-body-tube-bt-65-10-0-long-sem-pst-65l/https://www.payloadbay.com/index.php?page=Tools&action=SLOTGUIDE
I have to second another commenter: I like the BT-65 diameter tube. It fits nicely between the BT-60 and the BT-70 in the Estes tube selection. There is a fairly big jump in diameter from a BT-60 to a BT-70. I hope that Estes makes the BT-65 tubes available in a two-pack or three-pack, as is done for the BT-60 and BT-70.@brockrwood,
It looks like you have the right answer by now, but both Green Eggs and Olympus use a BT-65 tube. It is 1.796" in Diameter. My own measurement of the wall thickness is 0.022", but it could be single sample variance.
With a 0.022" wall, ID = 1.752"
With a more to Estes standard 0.021" wall, ID=1.754"
I've attached the press release from the Old rocket forum post.
Here are some corroborating links.
https://www.oldrocketforum.com/showthread.php?t=18149&page=1&pp=10&highlight=olympushttp://modelrocketbuilding.blogspot.com/2019/11/another-new-estes-kit.htmlhttp://modelrocketbuilding.blogspot.com/2020/08/estes-green-eggs-7301-build-part-1-parts.html
@Scott_650,
The tubes in the 2281 TARC small parts assortment were BT-56, not BT-65, which as I'm sure you are aware, is the same as Centuri ST-13 (OD 1.34") I ordered one specifically because it was the only way to get 18" ST-13 at the time. The current page for that item number has been removed from the current Estes website, but the wayback machine captured a parts list from the 2017 Estes website. The egg carrying portion of the small TARC assortment is ST-20 (2.04" OD).
http://web.archive.org/web/20170628...ckets/tarc/002281-tarc-small-parts-assortment
As for the PST-65 clear tubes on eRockets, if the dimensions listed are correct, then it is NOT true BT-65. It is sized more closely to the BT-65 coupler than the tube. At an OD of 1.74", it would slip fit inside BT-65.
Interestingly, BalsaMachining sells 34" coupler material for Aerotech 1.88" tube that matches BT-65 external diameter of 1.796". It does have a much thicker wall, however, at 0.034".
Here is a list of ~1.8" tubes:
BT-65 OD=1.796" (found on Scrambler, Green Eggs, and Olympus)
HBT-1800 OD=1.8" (found exclusively on Estes #2037 1:5 D-Region Tomahawk)
ST-18 OD=1.84" (Centuri tube, found on Semroc and Odd'l kits--currently seems to be unavailable in longer lengths)
LT-175 OD=1.84" (Centuri/Semroc heavy wall SLS tubing. 1.75" ID)
Aerotech 1.88" OD-1.88" (closer to 1.9" than 1.8")
@ZoomieG What's the length of the Green Eggs paper BT-65 tube? I want to put an entry in the OR parts database. If you have a suitable scale a mass measurement would be great too. TIA!!
Egg years?Interesting evolution here. In the classic era (1970s-1980s), the only 65 series tube that Estes made was the plastic PST-65 in 5.0" length, which was listed in the 1974 regular catalog as OD 1.796", ID 1.750", implying an 0.023" wall. This was used in the original K-37 Scrambler. I have a note that the notoriously error-filled 1974 custom parts catalog listed PST-65 with OD 1.641, which is patently bogus. The later #2072 Scrambler had a different design with a short section of ST-20.
I've got no idea why the Semroc clear 65 series tube has the OD set at the ID of the Estes one, basically making it coupler tube size. They do list the smaller dimensions on their site, but calling it PST-65 is a mistake because those dimensions are not at all compatible.
Now in the TARC era, Estes has brought in paper BT-65 size tubes, where the only authoritative mfr data (that I know of) is the specified diameter of the Green Eggs, given (to low precision) as 1.8", where there are both clear and paper tubes of that same size in the Green Eggs.
The 65 size is not ideal for TARC, where everything has settled down to BT-70 for longitudinally oriented egg years and BT-80 for sideways egg years. In those sizes you can get heavywall tubes and the Apogee foam egg protectors which are nearly foolproof.
@ZoomieG What's the length of the Green Eggs paper BT-65 tube? I want to put an entry in the OR parts database. If you have a suitable scale a mass measurement would be great too. TIA!!
The Green Eggs tube I just measured is 12".I don't actually have a Green Eggs kit. I do have an Olympus, which has a full 18" body tube. Based on the overall length differences, and the parts layouts on both the Estes website and Chris M.'s model building site, I would guess with high confidence that the Green Eggs body tube is 12" long.
Perhaps someone with a kit in hand can provide a measurement.
@brockrwood,
I've attached the press release from the Old rocket forum post.
I built one and I don't remember....but it's interesting that the instructions show what appears to be a three-fin slotted tube (as used on Green Eggs) but then no fin tabs...and of course Olympus has four fins anyway. https://estesrockets.com/wp-content/uploads/Instructions/007293_OLYMPUS.pdfInteresting that the press release states the Olympus has TTW fins, when it actually does not. (Unless they updated the kit in the 1-2 years since I build mine).
Interesting that the press release states the Olympus has TTW fins, when it actually does not. (Unless they updated the kit in the 1-2 years since I build mine).
TARC rules change each year so a team can't just refly a previous year's design. One of the changes they can make is orientation of the egg payload from lengthwise to sideways in the rocket, the latter requiring a wider body tube.Egg years?
It's almost perfect scale to build a 1/10th scale Patriot I have an Olmypus kit as a donor for just that someday
Can't find 29mm motor mount tubing or the proper 29mm Centering ring to go into the BT-65 body tube (Estes Olympus or Green Eggs).Estes has the
BT-65 body tube, https://estesrockets.com/product/046007-bt-65-body-tube/
Egg nose cone, https://estesrockets.com/product/030110-egg-capsule-nose-cone/
couplers https://estesrockets.com/product/030182-bt-65-tube-coupler/
motor mount centering rings for their 29 mm motor tube PN 068253
29mm motor tube https://estesrockets.com/product/031360-pro-series-ii-29-mm-engine-mount-tube/
They write about using them for TARC competitions to launch a hen's egg to 800 feet
It's almost perfect scale to build a 1/10th scale Patriot I have an Olmypus kit as a donor for just that someday
-Bob
I just built an Olympus (purchased 4-5 months ago) and I can confirm that the instructions show TTW fins, but it does not actually have TTW fins.I built one and I don't remember....but it's interesting that the instructions show what appears to be a three-fin slotted tube (as used on Green Eggs) but then no fin tabs...and of course Olympus has four fins anyway. https://estesrockets.com/wp-content/uploads/Instructions/007293_OLYMPUS.pdf
Green Eggs does have three TTW fins in its 12-inch-long main body tube.
The motor tube should be fairly easy. For example: semroc-body-tube-lt-115-bth-52-29mm-motor-tube-5-5-long-sem-lt-11555Can't find 29mm motor mount tubing or the proper 29mm Centering ring to go into the BT-65 body tube (Estes Olympus or Green Eggs).
Estes has the
BT-65 body tube, https://estesrockets.com/product/046007-bt-65-body-tube/
Egg nose cone, https://estesrockets.com/product/030110-egg-capsule-nose-cone/
couplers https://estesrockets.com/product/030182-bt-65-tube-coupler/
motor mount centering rings for their 29 mm motor tube PN 068253
29mm motor tube https://estesrockets.com/product/031360-pro-series-ii-29-mm-engine-mount-tube/
They write about using them for TARC competitions to launch a hen's egg to 800 feet
It's almost perfect scale to build a 1/10th scale Patriot I have an Olmypus kit as a donor for just that someday
-Bob
I like the look.I'm building an Olympus now with Partizon fins, lol...They are going the other way. Left was a goof...
Thank you. I like these rockets, unfortunately my last one(below) hangs in a tree...lolI like the look.
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