Weird Tube Size of Estes Olympus

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TigerHawk said:
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
Click to expand...
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.
 
I scratch built the Scrambler and parts list included a 60 to 65 balsa adapter and a clear payload section of 65.
Although not that common, that size has been around quite along time. Finding that size clear plastic for the payload bay was a challenge.
I can't remember now where I found it. Apogee had it listed at the time, but out of stock.

While catering to TARC, I'm willing to bet a minimum order is required for any size BT. Estes is probably putting that tube to use instead of having it sit around for years. TARC probably only uses a small percentage of a minimum order each year. So we end up with something different in size on the market for us. Personally, I like that size. I am also partial to the 56 size.

Since the new owners are hard at work doing what we all wish for as fast as they can, perhaps they are expanding sizes some too.
The diameter difference between a 60 and 70 is substantial, so I look forward to 65 if it becomes more common. It will allow greater designs working with adapters for 60 & 70. More variations on clusters, and be lighter. Yes, I would like to see the 65 readily available.
 
@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")
 

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ZoomieG said:
@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")
Click to expand...
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.

Bill Stine, are you reading this thread? Estes customers are asking Estes to make an accessories pack with two or three BT-65's in it! :)
 
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!!
 
Last edited:
caveduck said:
@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!!
Click to expand...

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.
 
caveduck said:
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!!
Click to expand...
Egg years?
 
ZoomieG said:
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.
Click to expand...
The Green Eggs tube I just measured is 12".
 
ZoomieG said:
@brockrwood,
I've attached the press release from the Old rocket forum post.
Click to expand...

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 built mine).
 
Last edited:
Spitfire222 said:
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).
Click to expand...
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.
 
Bruiser said:
It's almost perfect scale to build a 1/10th scale Patriot :) I have an Olmypus kit as a donor for just that someday :)
Click to expand...

Forgot to touch on this earlier: assuming you are talking about the MIM-104 Patriot Surface-to-Air Missile, it's diameter is 16". BT-65 tubing, at 1.8", is too large to be 1/10th.

Estes makes a 1/10 scale patriot. As it is BT-60 based, it's not perfect, but it's close.
https://estesrockets.com/product/002056-u-s-army-patriot-m-104/
 
"Forgot to touch on this earlier: assuming you are talking about the MIM-104 Patriot Surface-to-Air Missile, it's diameter is 16"

I realized that later that evening. I happened to review the size of the Patriot and I realized I remembered it wrong. It wasn't because of the tube diameter that it would make it (the Olympus) a good Patriot bash. It was the nose cone diameter to length ratio.

The nose cone is too long on the Estes kit, there's no boat tail, the oversize fins, and 18mm engines???. I know it's not supposed to be museum scale but I would call it "fun scale".

The Olympus would make a good bash with ply fins, 24mm "E" mount, boat tail and conduits. I'd call it "sport scale". Oh, and the JLCR would fit in the BT65 tube better.

You caught me, lol!

-Bob
 
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Bruiser said:
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
Click to expand...
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).
 
BEC said:
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.
Click to expand...
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.
 
George Rachor said:
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).
Click to expand...
The motor tube should be fairly easy. For example: semroc-body-tube-lt-115-bth-52-29mm-motor-tube-5-5-long-sem-lt-11555

I asked David Qualman over in Washougal to create a version of his baffle for the Green Eggs/Olympus and he has, though it is not yet listed on his site here: http://qualmanrocketry.com/Baffle BT plywood.html He certainly could make you the centering rings you need.

Another possible source might be James Cramton at Rocketry Works on Tucson.

It would be an ask for a new or custom part from either one.

Otherwise it's careful work with a Dremel sanding drum to enlarge the holes in the thin kit-supplied rings....not fun, but could be done.

There were parts that would have done it in a TARC parts assortment several years ago, but that seems to have disappeared from the Estes web site.
 
Last edited:
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 seems to just drop the item from the website when they run out, The standard 3" pro series nose cone is also missing.

It used to be much easier to find all the pro series parts as they had their own tab but then Estes re-did the website to make it easier :)

-Bob
 
Bruiser said:
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
Click to expand...

I've been mildly Goblin-obsessed lately. I look at that nose cone and it looks perfect for a modest upscale Goblin. And even comes with an ebay housing big enough for a Quark to do dual deployment!
 

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