Mounting advice for Featherweight Tracker

Hi all.

I have a couple of 54mm mid-powers (Aerotech Strong Arm and PM AGM-256 Pit Bull) on which I’d like to mount a Featherweight Tracker. I only have one tracker so it would need to be fairly easy to switch between rockets.

Neither of these rockets have e-bays, and the PM in particular does not have a ton of room inside. It seems like the best approach might be a nose cone mount but I’m not sure on how best to do that.

Any advice would be much appreciated. Thanks!

I have been using a 3D printed nosecone bay mount for my Featherweight Trackers. In spite of its simplicity, it's very robust and reliable.

Voyager1 said:

I have been using a 3D printed nosecone bay mount for my Featherweight Trackers. In spite of its simplicity, it's very robust and reliable.

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That's super cool. Your fancy screw-together nose cone got me looking at payload nose cones. The PM Intelli-cones look good, but they're expensive. Also the 65mm (I wrote 54mm above, incorrectly) Intelli-cone is the same length as the stock Pit Bull cone but about 2" shorter than the Strong Arm cone, so it would throw off the lines some.

I wasn't able to find payload nose cones from any other source. I understand I can just add a standard payload bay and tightly fit the existing nose cone, but I don't want to change the rocket length if I can avoid it.

Thanks!

The nosecone avbay kits are available from MAC Performance Rocketry at

https://macperformancerocketry.com/collections/nosecone-bay-kits/products/pinnacle-nosecone-bay-kits

I use them in all my nosecones. They are quite cheap, but very good.

I make my own out of aircraft grade plywood using a Dremel with the circle cutting attachment. The cuts can be a little rough (and they're not as pretty as 3D printed), but a little sanding and good epoxy and they fit like a glove. I've attached a design diagram for a 4" nose cone. The inner fixed bulkhead nestles up against the NC shoulder and is epoxied in place; I inject epoxy on the back side of that bulkhead so it's epoxied on both sides. The removable bulkhead is attached to the fixed bulkhead using brad mounted t-nuts (I add screws on the bigger bulkheads, don't on the smaller ones) and the appropriate sized machine screws. Lock nuts are epoxied on the back of the weld nuts. A forged eye bolt is attached in the center of the removable bulkhead for recovery harness attachment. Dimensions of parts for various NC sizes:

2.6" to 3" NC- 3/16" plywood, 6-32 t-nuts, 1/4" eye bolt
4" NC - 1/4" plywood, 8-32 t-nuts, 1/4" eye bolt
5" - 6" NC - 5/16"plywood, 10-24 t-nuts, 5/16" eye bolt
> 6" NC - not there yet...go bigger!

I would do 3D printed components but I don't have a printer and having them printed can be pricey, especially if I miss the dimension measurements by even a small amount (and have to re-jigger and get printed again - been there, done that).

If you have a Dremel it's a cheap way to go; I'm making these for all of my nose cones going forward (I can add weight (washers) as well as a tracker in any design this way. An Eggfinder fits nicely into this design.)

Try Lab Rat Rocketry. He has 3D printed products just for this.

Voyager1 said:

The nosecone avbay kits are available from MAC Performance Rocketry...I use them in all my nosecones.

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Looks very cool but I see that they offer 54mm and 3” but not 65mm.

Lab Rat Rocketry... They are great and super easy to move between your 38mm and 54mm rockets.

ABlock said:

Looks very cool but I see that they offer 54mm and 3” but not 65mm.

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I have the sled from LRR for the eggfinder, but needed a bulkhead for 65mm, which is why I rolled my own with plywood.

Thanks for the plug guys.

In stock and ready to ship: https://www.labratrocketry.com/product-page/tracker-sled-featherweight

For 66mm I recommend either going with a removal bulkhead (make from a coupler bulkhead and CR), or making a tracking tube (place a 38mm tube in the nosecone using a coupler CR, then put a plastic motor retainer on the aft end). With the tracking tube you just put the sled on a bulkhead, and use the retainer to hold it in the tube.

I have been making all my nose cone av bays with a centering ring and a motor tube (38 if < 75mm rocket and 54 if above that). at the end of the motor tube, I put on a AeroPac retainer to hold the electronics in. Makes it easy to switch between rockets. My sled has been as simple as a piece of thin plywood cut the right length to fit tight to what I use now (3D printed sleds). I use the AeroPac also for my av bay mid rocket for the Raven4. The last few flights I have been able to use a 3D printed sled with interchangable charge wells and an O-Ring for the forward seal. Simply screw it in and tighten the AeroPac. Since my AvBay only has ejection forces on it, I may try 3D printing something to replace the AeroPac on future rockets - just for cost savings - (my shock cord is epoxied to the coupler and goes all the way through the rocket).

Not sure if I'm attaching the image correctly here but will try... the base of both AvBays are sized currently for the AeroPac.

kjs said:

I have been making all my nose cone av bays with a centering ring and a motor tube (38 if < 75mm rocket and 54 if above that). at the end of the motor tube, I put on a AeroPac retainer to hold the electronics in.

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Thanks. How do you attach the shock cord to the nose cone in this case?

ABlock said:

Thanks. How do you attach the shock cord to the nose cone in this case?

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I notch the centering ring holding the motor tube in place and epoxy kevlar to it with a short loop at the end. the I attach my other kevlar lengths to that. I don't use any metal or eye bolts anymore... for the AvBay (center of the rocket), I run enough thick kevlar to give me a loop at the bottom below the av bay and enough out the top to go past the end of the body tube. I may use thinner kevlar for the shock cords but I always go heavy on these short pieces...

Pictures attached... this was a 4" rocket so 54 mm bays - and before I started using a 3D printer.

Here is possibly a better pic that also includes the 3D sled... again overkill on the short piece of kevlar but it is short - and then I can attach to it whatever I need. I am <cough> known for very long shock cords... my theory is "if you can walk in the general direction of where it landed, you should trip over your shock cord..."