# Launch Lug Dimensions

#### jqavins

##### Слава Україні
TRF Supporter
I'm looking for the actual dimensions of a 3/32" launch lug. Let's say an Estes 2/32" lug.

The ID has to be a little smidgeon more than 3/32", since it slides easily onto and off of a 3/32 rod. And it's really the OD I'm interested in.

I would take a reasonable guess, or measure one, which is easier said than done since they are so crushable in calipers. I tried estesrockets.com to no avail. So does anyone happen to know?

#### neil_w

##### OpenRocketeer
TRF Supporter
Don't have one in front of me to measure, but the OR parts database (which is now using @caveduck 's excellent parts library) lists OD/ID for the Estes 3/16" lug at 0.227"/0.210". (I assume you mean 3/16").

Balsa Machining's is slightly larger at 0.240"/0.219".

#### jqavins

##### Слава Україні
TRF Supporter
Yes, 3/16". Thanks. The gap between three circles of equal diameter, pushed up together, can accommodate an inscribed circle of about 0.155 times the larger circles' size. So, to fit a 3/16 launch lug in the space between tube fins in a typical 6 tube arrangement, the tubes' ODs must be 0.240" ÷ 0.155 = 1.548". To do without the lug at all, i.e. it the circle inscribed on the gap has the ID of the lug that isn't there, the tube OD has to be 0.219" ÷ 0.155 = 1.413". A BT-60's OD is 1.64", so a lug would fit inside the gap, but would need a wee bit of filler.

A BT-55's OD is 1.33", so too small. A 1/8" lug would probably fit.

(0.155 is not a calculated figure, but one I found by trial and error using a Visio drawing. I could calculate it if I were in the mood. Come to think of it, I could probably have looked it up; d'oh.)

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