Weird Tube Size of Estes Olympus

[brockrwood]

I picked up an Olympus kit at my local Hobby Lobby a few months ago. It seemed like a low price for a big rocket with a clear payload bay.

I recently examind it more closely. The body tube is 1.8 inches in diameter. That is not a BT-60. That is not a BT-70. It is somewhere between a BT-60 and a BT-70. Odd. Is this a new Estes tube size? Is it a re-introduction of some long ago discontinued tube size?

See pics.

 

[jmasterj]

I don't have an answer for you, but it's the same size as the Green Eggs. The Olympus doesn't have through-wall fins, though.

 

[brockrwood]

I don't have an answer for you, but it's the same size as the Green Eggs. The Olympus doesn't have through-wall fins, though.

Is there any reliable way to cut fin slots into an LPR body tube that does not come with pre-cut slots? I have considered just marking the tube and then cutting a thin slit with a hobby knife. Then, with a mini-file, very carefully and slowly enlarging the slit all the way down the slit. What do you think? My fear is that if I cut my own slots for fins, I will mess it up and ruin the tube. I guess ruining one LPR tube is not the end of the world.

 

[mh9162013]

Is there any reliable way to cut fin slots into an LPR body tube that does not come with pre-cut slots?

I've never used that method, but it comes from TVM at Apogee, so the method comes from a reputable source. If I were inclined to cut my own fin slots, that's the method I'd try.

 

[jmasterj]

I haven't done it myself, but if you get a payload bay marking guide and take the cutting slow I think it would be fine. I'm planning on using my angle iron to try to keep things straight whenever I get to trying it.

 

[DigBaddy]

Sounds like BT-65....

 

[samb]

There is a BT-65 not very well documented on the website. TARC rules say the payload (egg) must be 45mm or less in diameter. Coincidence? I don't think so.

https://estesrockets.com/?s=tarc&search_id=1

 

[SecondRow]

I picked up an Olympus kit at my local Hobby Lobby a few months ago. It seemed like a low price for a big rocket with a clear payload bay.

I recently examind it more closely. The body tube is 1.8 inches in diameter. That is not a BT-60. That is not a BT-70. It is somewhere between a BT-60 and a BT-70. Odd. Is this a new Estes tube size? Is it a re-introduction of some long ago discontinued tube size?

See pics.

View attachment 524171

View attachment 524172

View attachment 524173

Maybe a Centuri ST-18 tube? It wouldn't be unheard of for Estes to use Centuri tubes. For example, the Mercury Redstone uses the Centuri ST-20, which is a 2 inch tube.

 

[SecondRow]

Here's the link for the Estes BT65 tube coupler. O.D. of the coupler is 1.744 in.

https://estesrockets.com/product/030182-bt-65-tube-coupler/

 

[rharshberger]

I have a Olympus (unbuilt) but have not measured the airframe, sounds like it could be similar to the T188-34 airframe tube that Balsa Machining Service sells.

 

[brockrwood]

I've never used that method, but it comes from TVM at Apogee, so the method comes from a reputable source. If I were inclined to cut my own fin slots, that's the method I'd try.

Hmm. The core of Tim’s method seems to be to cut the two ends of the slot (3/32”, 1/8”, or what not). Then you use the angle aluminum to get a nice, straight cut down both sides of the slot with the hobby knife. Makes sense. Patience and a steady hand required.

I guess it is time to invest in some angle aluminum. I have one long strip (not sure of the size) for medium to small tubes. I need some other sizes. I also need to find my hacksaw.

 

[brockrwood]

Maybe a Centuri ST-18 tube? It wouldn't be unheard of for Estes to use Centuri tubes. For example, the Mercury Redstone uses the Centuri ST-20, which is a 2 inch tube.

It seems like the Olympus tube is a hair smaller than the diameter of a Centuri ST-18 based on the erockets website.

 

[brockrwood]

Here's the link for the Estes BT65 tube coupler. O.D. of the coupler is 1.744 in.

https://estesrockets.com/product/030182-bt-65-tube-coupler/

I think you nailed it. This coupler for a “BT-65” body tube, whatever that is, looks like it is just a hair smaller than the Olympus “1.8 inch” body tube.

 

[brockrwood]

There is a BT-65 not very well documented on the website. TARC rules say the payload (egg) must be 45mm or less in diameter. Coincidence? I don't think so.

https://estesrockets.com/?s=tarc&search_id=1

I think you are onto something here. The outside diameter of the BT-65 coupler is 1.744 inches. That is 44.2976 mm. So the “BT-65” body tube would have an inside diameter of just a little more 1.744 inches. Just enough room for a 45 mm egg.

Estes is mum on the inside and outside diameter of the “BT-65” body tube but is a reasonable guess that the Olympus uses a BT-65 borrowed from the TARC parts. Makes sense. It is an egg lofter after all.

 

[neil_w]

Is there any reliable way to cut fin slots into an LPR body tube that does not come with pre-cut slots?

Just hold (or tape, or strap) a piece of aluminum angle against the tube and use it as a cutting guide. It’s incredibly easy. Err slightly on the too-small side rather than too wide if possible, although *slightly* oversized is not much of a problem.

Inserting a coupler in the tube to support it while cutting helps.

 

[BEC]

Yup - Olympus and Green Eggs have a BT-65 main tube as well as payload tube. The old Scrambler only had BT-65 for the payload tube, but the body was BT-60.

David Qualman has created a baffle for these models. They are not yet shown on this page: http://www.qualmanrocketry.com/Baffle BT plywood.html so just drop him an email. I have test-fit a pre-production version and it fits nicely.

 

[Rocketjunkie]

Done it a lot for high power and LOC tubes. Mark fin locations and the length of the tab. Using a sharp blade and multiple light passes, cut along the fin mark, then the fin thickness to one side. Repeat for the other fins making sure you cut to the same side of the marks and cut the top and bottom where the fin slot is at the end of the tab.

 

[smstachwick]

From the Estes website:

“The BT-65 Body Tube is 23.5 inches in length and can be used to create a single main body tube rocket capable of handling our 29 mm E16 or F15 model rocket engines or by incorporating the included blow molded BT-65 nose cone and tube coupler into the design, it is possible to create a TARC wining rocket that is over 4 feet tall! To power this huge rocket, we’d recommend using our 29 mm to BT-65 Laser Cut Ring Set (PN 068253) and related engine mounting components that should easily launch this rocket with hen’s egg to the TARC competition requirement of 800 feet!”

https://estesrockets.com/product/046007-bt-65-body-tube/
No dimensions, sadly, but apparently they support the BT-65 size with matching components to some degree. It just doesn’t seem to be super common. Most TARC rockets I have seen are far more advanced in construction and design and use composite motors like the AeroTech F67W instead of Estes’ in-house black powder E16s and F15s.

It also looks like they haven’t updated the page in some time, the altitude target last season was 835 (?) ft.

 

[Bruiser]

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

 

[rharshberger]

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

Aren't hens the only one that lay eggs....

 

[brockrwood]

I picked up an Olympus kit at my local Hobby Lobby a few months ago. It seemed like a low price for a big rocket with a clear payload bay.

I recently examind it more closely. The body tube is 1.8 inches in diameter. That is not a BT-60. That is not a BT-70. It is somewhere between a BT-60 and a BT-70. Odd. Is this a new Estes tube size? Is it a re-introduction of some long ago discontinued tube size?

See pics.

View attachment 524171

View attachment 524172

View attachment 524173

Slightly off-topic: See the “helping hands” magnifying glass and adjustable alligator clips in the first pic? The alligator clips are cheap and just crush and fall out. The set screws won’t twist tight enough to “set”. I wish I could find a source for a really high quality, “pro” version of the helping hands device. Anybody know of one? This is for my electronics hobby. Which sometimes overlaps with model rocketry hobby.

 

[WillMarchant]

Slightly off-topic: See the “helping hands” magnifying glass and adjustable alligator clips in the first pic? The alligator clips are cheap and just crush and fall out. The set screws won’t twist tight enough to “set”. I wish I could find a source for a really high quality, “pro” version of the helping hands device. Anybody know of one? This is for my electronics hobby. Which sometimes overlaps with model rocketry hobby.

I got one of the Hobby Creek https://www.adafruit.com/product/3019 upgrades for my panavise. Looks like they’re our of business (sob) but Amazon has knock-offs. Try a search for “panavise 3rd hand”.

 

[Scott_650]

The now now longer available #2281 TARC Small Parts Assortment had the same sized tube - glad I bought one before Estes stopped offering the parts assortment on their website, it looks like it’ll build up into a nice looking payloader.

 

[WillMarchant]

The Green Eggs is also BT-65. I like the white/clear Olympus payload bay and replace the green/yellow stock parts on the GE.

 

[goose_in_co]

Slightly off-topic: See the “helping hands” magnifying glass and adjustable alligator clips in the first pic? The alligator clips are cheap and just crush and fall out. The set screws won’t twist tight enough to “set”. I wish I could find a source for a really high quality, “pro” version of the helping hands device. Anybody know of one? This is for my electronics hobby. Which sometimes overlaps with model rocketry hobby.

Brock, Find a brass or aluminum rod, and cut a short section to put into those alligator clips, that will keep them from crushing. Or I suppose any bolt of the proper diameter could also be used. All you are trying to do is to keep those tubes on the alligator clips from compressing, and any round metal object should do that.
Goose

 

[bjphoenix]

Is there any reliable way to cut fin slots into an LPR body tube that does not come with pre-cut slots? I have considered just marking the tube and then cutting a thin slit with a hobby knife. Then, with a mini-file, very carefully and slowly enlarging the slit all the way down the slit. What do you think? My fear is that if I cut my own slots for fins, I will mess it up and ruin the tube. I guess ruining one LPR tube is not the end of the world.

I cut some BT-60 recently to make side pods that overlap the main airframe. I used an old piece of steel angle from the hardware store, 1" x 1". I just held it in place and ran the hobby knife along the edge of the angle. I used a new sharp knife blade, the ones that fit the small diameter handle because they are thinner. It took 3 light passes to cut all the way through the tube.
Depending on the length of the slots and whether they go all the way to the end of the tube, your tubes can be hard to hold once you have cut all the way through. I did 2 things to help with this. Since I knew it would take 3 cuts to go all the way through, I made 2 light cuts along each line. Then for the last cut I started at one end and cut a short length all the way through, 1 or 2" long, both sides of the slot. Then I moved up and cut another 1 or 2", until I had completed the slot.

 

[WillMarchant]

I got one of the Hobby Creek https://www.adafruit.com/product/3019 upgrades for my panavise. Looks like they’re our of business (sob) but Amazon has knock-offs. Try a search for “panavise 3rd hand”.

Looks like https://www.digikey.com/en/products...QL-kEU6BFR-VazqDoQl8-9-QN0PGlrURoCkZ4QAvD_BwE still has some in stock.

 

[Bruiser]

Maybe they say "hen's egg's" so nobody tries to launch a dame's egg. That would result in a big goose egg for a score

But then again a female ostrich is also a hen and I don't think even the smallest ostrich egg would be successful...

-Bob

 

[brockrwood]

Looks like https://www.digikey.com/en/products/detail/adafruit-industries-llc/3019/7323618?utm_adgroup=Specialized Tools&utm_source=google&utm_medium=cpc&utm_campaign=Shopping_Product_Tools&utm_term=&utm_content=Specialized Tools&gclid=CjwKCAjwwdWVBhA4EiwAjcYJEKm4CNR8laOHe-qKiC33NtQL-kEU6BFR-VazqDoQl8-9-QN0PGlrURoCkZ4QAvD_BwE still has some in stock.

That thing looks awesome!

 

[Scott_650]

The now now longer available #2281 TARC Small Parts Assortment had the same sized tube - glad I bought one before Estes stopped offering the parts assortment on their website, it looks like it’ll build up into a nice looking payloader.