BT-20 Nose cone fit problems

[khabuda]

Does anyone have any leads on BT-20 nosecones that don't overhang the tube? I ordered tubes and some of the PNC-18 nosecones from Apogee, and the OD of the nosecones is pretty significantly larger than the OD of the tubes. I ordered some of the white ones from Rocketarium to see if those fit any better, but I'm looking for any tips. The yellow ones are kind of a pain to sand down to a perfect fit, but if that's what everyone does, then I'll just work on a better process for that.

 

[Art Upton]

Have you tried fitting a white Estes nose cone? Never seen yellow ones for BT-20

 

[RocketTree]

The Rocketarium ones you ordered should be a good (or exact) fit for thin wall BT-20 tubes. The one in your photo looks like it was made for a thick wall tube.

 

[BABAR]

Does anyone have any leads on BT-20 nosecones that don't overhang the tube? I ordered tubes and some of the PNC-18 nosecones from Apogee, and the OD of the nosecones is pretty significantly larger than the OD of the tubes. I ordered some of the white ones from Rocketarium to see if those fit any better, but I'm looking for any tips. The yellow ones are kind of a pain to sand down to a perfect fit, but if that's what everyone does, then I'll just work on a better process for that.

Maybe contact Apogee customer service?

is this a standard BT-20 (I am guessing yes)

also take a look at the specs for the nose cone on the Apogee site, did they SAY the outer diameter was not a match? If not, I’d say they owe you some replacements. At least if you let them know they can update it on their site so no one else has to go down same rabbit hole.


I just looked at the web site, and the yellow nose cone outside diameter is listed as 0.736”

https://www.apogeerockets.com/Building_Supplies/Nose_Cones/Low_Mid_Power_Nose_Cones/PNC-18B
which IS also the listed outside diameter of the BT-20.

https://www.apogeerockets.com/Build...er_Tubes/18mm_x_18_Body_Tube_Estes_BT-20_size
curious if this is a manufacturer QC Problem or the manufacturer mold maker just messed up. In any case, would be curious to see what Apogee says when you contact them.

straight trails (unless you build like me, then I wish you a straight trajectory with cool corkscrew trails!)

 

[SolarYellow]

Is that the B or D version? Can you measure the OD with calipers and tell us to 0.001" what it measures?

It looks like it might work well on ST-7.

ST-7

Centuri Standard Tube 7

BNB-7 BTC-7 HTC-7

BC-7

0.759

0.715

0.022

18

12.4

The Estes PNC-20 cone family generally fits with less overhang than that. Buy them in the nose cone pack, as a bulk pack of Vikings, or as a ten-pack of nose cones only from AC Supply.

 

[mh9162013]

The yellow ones from Apogee are likely designed for thick-walled main body tubes. I know this is true for the nose cone that comes with the Apprentice (a BT-50 rocket), as its main body tube is thick-walled and using an Estes cone with it leaves a somewhat noticeable shoulder/edge.

If you're looking for a plastic nose cone for BT-20 rockets, you're basically stuck with whatever Apogee and Estes have. Estes has a decent selection with its variety pack that fits regular thickness BT-20 tubing just fine.

 

[khabuda]

Is that the B or D version? Can you measure the OD with calipers and tell us to 0.001" what it measures?

It looks like it might work well on ST-7.

ST-7

Centuri Standard Tube 7

BNB-7 BTC-7 HTC-7

BC-7

0.759

0.715

0.022

18

12.4

The Estes PNC-20 cone family generally fits with less overhang than that. Buy them in the nose cone pack, as a bulk pack of Vikings, or as a ten-pack of nose cones only from AC Supply.

Thank you for the tip on AC supply. I'll give those a shot if the rocketarium ones don't fit well. I'll have to measure the ones I have from Apogee later.

 

[khabuda]

The yellow ones from Apogee are likely designed for thick-walled main body tubes. I know this is true for the nose cone that comes with the Apprentice (a BT-50 rocket), as its main body tube is thick-walled and using an Estes cone with it leaves a somewhat noticeable shoulder/edge.

If you're looking for a plastic nose cone for BT-20 rockets, you're basically stuck with whatever Apogee and Estes have. Estes has a decent selection with its variety pack that fits regular thickness BT-20 tubing just fine.

The

Maybe contact Apogee customer service?

is this a standard BT-20 (I am guessing yes)

also take a look at the specs for the nose cone on the Apogee site, did they SAY the outer diameter was not a match? If not, I’d say they owe you some replacements. At least if you let them know they can update it on their site so no one else has to go down same rabbit hole.


I just looked at the web site, and the yellow nose cone outside diameter is listed as 0.736”

https://www.apogeerockets.com/Building_Supplies/Nose_Cones/Low_Mid_Power_Nose_Cones/PNC-18B
which IS also the listed outside diameter of the BT-20.

https://www.apogeerockets.com/Build...er_Tubes/18mm_x_18_Body_Tube_Estes_BT-20_size
curious if this is a manufacturer QC Problem or the manufacturer mold maker just messed up. In any case, would be curious to see what Apogee says when you contact them.

straight trails (unless you build like me, then I wish you a straight trajectory with cool corkscrew trails!)

I reached out to them earlier and the reply I got was basically "we checked the stock that we have and see the same problem". I didn't ask for them to address it really since it's a cheap enough part. I've been buying everything through them since I'm in Colorado and the shipping is really fast, so the one-stop-shopping was easier. They don't advertise a thick walled BT-20 or thick walled BT-20 nose cones, so I'm assuming they're stocking these parts to be compatible. In any case, they know now, so hopefully they don't keep selling the existing stock that way. No worries though. I'm new to scratch building, and this is all a fun process even when there are hiccups.

 

[tsmith1315]

If you’re okay with balsa, check with BMS. Their service is super:

https://www.balsamachining.com/#

Great selection of tubes, as well.

 

[SolarYellow]

I asked Apogee customer service about the PNC-18C. They said, "The nose cone is roughly 2mm wider in diameter than the BT-20 tubes."

Unfortunately, that's kinda a no-man's land at 0.816". Bigger than BT-20+ and not quite as big as BT-40.

 

[khabuda]

I asked Apogee customer service about the PNC-18C. They said, "The nose cone is roughly 2mm wider in diameter than the BT-20 tubes."

Unfortunately, that's kinda a no-man's land at 0.816". Bigger than BT-20+ and not quite as big as BT-40.

I appreciate you looking at it. I ended up ordering the Estes nosecones. I am trying to work through all of the BT-20 projects I can think of, so I'm collecting a lot of parts. I'm still working on my L1 cert, but it's nice to have cheaper things to tinker with and practice modeling in openrocket, and it's even nicer to have projects to launch all day at an event rather than just my big one.

 

[SolarYellow]

I appreciate you looking at it. I ended up ordering the Estes nosecones. I am trying to work through all of the BT-20 projects I can think of, so I'm collecting a lot of parts.

You're welcome. I picked up the Viking bulk pack for just that reason - lots of white body tubes and nose cones for cheap.

 

[BABAR]

I asked Apogee customer service about the PNC-18C. They said, "The nose cone is roughly 2mm wider in diameter than the BT-20 tubes."

Unfortunately, that's kinda a no-man's land at 0.816". Bigger than BT-20+ and not quite as big as BT-40.

Apogee has a rep for being the Cadillac of stores for rocketry.

I just looked at the web site. Is this the nose cone you are talking about (PNC-18C)

https://www.apogeerockets.com/Building_Supplies/Nose_Cones/Low_Mid_Power_Nose_Cones/PNC-18C
from web site, outside diameter Outer Diameter: 0.736" (1.87 cm)

which is the same as their BT-20 body tube.

https://www.apogeerockets.com/Build...er_Tubes/18mm_x_18_Body_Tube_Estes_BT-20_size

• Outer Diameter: 0.736" (1.87 cm)

It does seem to me that, since the person said that to you, they SHOULD correct their site to reflect the error (OD 2.07 cm, not 1.87 cm), AND since it doesn't really fit the standard BT-20 (at least not well) IMO they ought to have a special note on there that it doesn't fit. Also think they should have offered to make this right for you, either refund your money or (better) send you replacement "real" 1.87OD nose cone or cones for free.

Really surprises me, I expect better from them.

 

[SolarYellow]

I'm not the one with this problem. I just got caught up in the attempt to understand it.

 

[Ez2cDave]

I asked Apogee customer service about the PNC-18C. They said, "The nose cone is roughly 2mm wider in diameter than the BT-20 tubes."

Unfortunately, that's kinda a no-man's land at 0.816". Bigger than BT-20+ and not quite as big as BT-40.

BT-30 / .765" OD / .725" ID . . .

Also, T20Q ( Quest ) .787x.748 MPC/Quest T20

Balsa Machining Service has both of them.

https://www.balsamachining.com

Dave F.

 

[Paul Howard]

Does anyone have any leads on BT-20 nosecones that don't overhang the tube? I ordered tubes and some of the PNC-18 nosecones from Apogee, and the OD of the nosecones is pretty significantly larger than the OD of the tubes. I ordered some of the white ones from Rocketarium to see if those fit any better, but I'm looking for any tips. The yellow ones are kind of a pain to sand down to a perfect fit, but if that's what everyone does, then I'll just work on a better process for that.

Interesting, for me that fit would be Perfect. I always wrap 1 or 2 layers of copy-paper rings around the top of the body tube for longevity and "zipper-resistance", so to me that extra diameter overhang would match the reinforcement wraps nicely.

That's my 2 Centavos -PTH

 

[SolarYellow]

I've discovered there's also a BT-20H out there, with standard BT-20 ID but 0.021-in wall thickness.

 

[BEC]

That yellow nose cone fits Centuri ST-7 tubing better than BT-20. According to @hcmbanjo they were originally made for/by Starlight rockets. More in a YORF thread where I research and build a clone of the original Centuri Viking (from which the Estes model is descended, but which shares no common parts) here: https://www.oldrocketforum.com/showthread.php?t=17688

 

[SolarYellow]

Thanks for posting that link. hcmbanjo's post https://www.oldrocketforum.com/showpost.php?p=226975&postcount=13 and your nose cone comparison photo are in my archives now.

I have an Estes Viking bulk pack and the fins are so bubbled/bent/curved/warped as to be worse than useless. If I had a laser cutter, I might be able to make centering rings out of them or something. Other than that, they are fodder for the recycling bin.