Rail tolerances and a goofup of mine

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Bill S

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I have a rocket I'm building, and the forward rail button is a bit off - I had drilled the hole in the tube, and noticed it had wandered a bit off the desired position. I had intended to wallow out the hole a bit in the correct direction, but my son distracted me and I forgot, epoxying the rail button flange in the tube, only to notice later that it is crooked. I estimate it is off about 1/32nd or so, not quite an 1/16th. Maybe 3-4 degrees misaligned?

So my question is this: how tolerant of misalignment are 1010 rails? I don't have a rail section on hand to try and see for myself. I'd hate to have to somehow remove the button flange, patch up the hole with a patch on the tube interior, and re-do it in a different location.
 
It is fairly tolerant. Unistrut is much less tolerant than 1010 and 1515. I keep a small 2-foot section of each type to test.
 
It is fairly tolerant. Unistrut is much less tolerant than 1010 and 1515. I keep a small 2-foot section of each type to test.

I had previously thought to buy a 3 or 4' section to keep on hand for testing, but the shipping was more than the cost of the rail. I can see that I really need to keep a section on hand.

Lesson learned: check and recheck alignment before breaking out the epoxy, and recheck everything after the boy distracts me. :)

As I haven't yet glued the tube to the fin/motor can yet, I think I may be able to widen the fin slots on one side and rotate the tube a little. I'll report back on that later today.
 
First, ad a pic or 2 for us to see. As chuck said a 1010 rail has some slop in it for the buttons we use. And if you order from Grainger and pick up there, shipping way cheaper than home delivery.
 
I ended up sucking it up and ordered 3' of 1010 rail from 80/20.net. Close to $40 for a 3' sectionf (Grainger only had 6' sections, which is way too long for me, as I fly at club launches and don't even have an launch pad or controller, etc). MSC had a 4' section for a very similar price. Ugh.

It looks like my idea of wallowing out the rear button hole, and trimming a tiny bit of body tube material on one side of the fin slots should work, so that's what I am going to do.
 
Most 1010 buttons work on 1515 rails with no issues (obviously, this varies with the button/rail combo, so not universally true). Anecdotally, all the 1010 buttons I have work on the 1515 rails at MDRA, METRA and URRG. That would give you plenty of slop if your buttons are slightly misaligned. This also helps when you are at a crowded launch and there is a 2 hour wait for the 1010 rails, but the 1515 rails are empty :)
 
Which I do not get. We have folks trying to fly a 40 pound rocket on 1010 buttons.

Yeah, never understood this. At Red Glare last year, there was literally a 2 hour wait in the "chute" for the B rack (1010 rails) and the C rack was barely used for most of the iterations. I have tried mentoring and educating on this, but it always happens, so I just tend to default to the 1515 rails and let the battle for the 1010 rails resolve itself.
 
The same thing happened at NSL 2022. We had seven open pads at high power on the left. I am not sure if it was laziness to walk another 100+ feet or just not thinking.
 
Which I do not get. We have folks trying to fly a 40 pound rocket on 1010 buttons.
40# rocket no sweat with 1010 buttons/rail, BTW.

Most clubs probably have fewer 1515 rails vs. 1010 due to cost and usage and heavier pads needed depending upon your infrastructure.

If you have flyers waiting to get pad access due to shortage of rails, buy more. That's what we have done. Use your TRA PIP for this. That's why they provide it.

Flyers tend to want to fly off rails that are needlessly long. 12' rails aren't needed when an 8' will do. That right there is where the education needs to occur.

--Lance.
 
I discovered that part of my problem was that the piece of wood that I had glued the rear rail button flange to, then glued to the rear centering ring was a few degrees off. The rail button flange shaft was 3-5 degrees off. So that wasn't helping either...

After going through the hassle of widening the fin slots on one side, and sanding, etc, only to have little to no difference evident, I looked at the rear mount more closely. Ugh.

So I removed the rear flange (mount is really stuck on the rear ring, not going anywhere w/o damaging something. I'll be using a piece of BT-80 coupler, cut down to fit between the fin tabs, and up against the main body tube so as to strengthen it so the flange won't rip out due to bad luck or something. Then re-drill the hole for the rear button an inch ahead of the first one.

Wow, what a hassle. My previous rocket, in which I didn't do a removeable fin can, was a lot easier; drill 2 holes, insert flanges and glue in with buttons tightened down, done.
 
40# rocket no sweat with 1010 buttons/rail, BTW.

Most clubs probably have fewer 1515 rails vs. 1010 due to cost and usage and heavier pads needed depending upon your infrastructure.

If you have flyers waiting to get pad access due to shortage of rails, buy more. That's what we have done. Use your TRA PIP for this. That's why they provide it.

Flyers tend to want to fly off rails that are needlessly long. 12' rails aren't needed when an 8' will do. That right there is where the education needs to occur.

--Lance.
We have 64 pads and 15-20 1010 rails. That is plenty.
 
I discovered that part of my problem was that the piece of wood that I had glued the rear rail button flange to, then glued to the rear centering ring was a few degrees off. The rail button flange shaft was 3-5 degrees off. So that wasn't helping either...

After going through the hassle of widening the fin slots on one side, and sanding, etc, only to have little to no difference evident, I looked at the rear mount more closely. Ugh.

So I removed the rear flange (mount is really stuck on the rear ring, not going anywhere w/o damaging something. I'll be using a piece of BT-80 coupler, cut down to fit between the fin tabs, and up against the main body tube so as to strengthen it so the flange won't rip out due to bad luck or something. Then re-drill the hole for the rear button an inch ahead of the first one.

Wow, what a hassle. My previous rocket, in which I didn't do a removeable fin can, was a lot easier; drill 2 holes, insert flanges and glue in with buttons tightened down, done.
Glad to see you have a solution.
 
Yeah, never understood this. At Red Glare last year, there was literally a 2 hour wait in the "chute" for the B rack (1010 rails) and the C rack was barely used for most of the iterations. I have tried mentoring and educating on this, but it always happens, so I just tend to default to the 1515 rails and let the battle for the 1010 rails resolve itself.
Thanks, I need to remember that at Red Glare this year.
And remember to try my 1010 buttons on the 1515 rails at the next MDRA launch (February 4th).
 
Thanks, I need to remember that at Red Glare this year.
And remember to try my 1010 buttons on the 1515 rails at the next MDRA launch (February 4th).

Good luck Walt - the winter launches are great times to experiment when there are relatively few people there and you often have the run of the place.
 
At Red Glare last year, there was literally a 2 hour wait in the "chute" for the B rack (1010 rails) and the C rack was barely used for most of the iterations. I have tried mentoring and educating on this, but it always happens, so I just tend to default to the 1515 rails and let the battle for the 1010 rails resolve itself.

This is part of the reason I am not sure I even want to bother going to Red Glare this year. Long wait to use the 1010 rails, plus only ONE 1/4" rod pad available. We had a couple rockets (Executioner, Super Big Bertha) that were still using 1/4" launch lugs, as converting them to 1010 buttons was going to be pretty challenging. Long wait, we got in like 4-5 launches each, despite being there all day Saturday. That and the launch system not being very reliable on the A pads... when you have a fail to launch, igniter didn't ignite, clips were clean and solidly attached, we had to think what the heck? We never did get either of those rockets launched, due to multiple fail to launches, and only one 1/4" pad available.
 
Yeah, never understood this. At Red Glare last year, there was literally a 2 hour wait in the "chute" for the B rack (1010 rails) and the C rack was barely used for most of the iterations. I have tried mentoring and educating on this, but it always happens, so I just tend to default to the 1515 rails and let the battle for the 1010 rails resolve itself.
Ugh, pad and que management at RG last year was the worst I've ever seen it. I even volunteered to assist que management Saturday afternoon and Sunday, was turned down both days. More folks being released to pad up than pads available turned the field into somewhat of a foot race and lots of not-so-soft angry mutterings. And less than 1 HP launch an hour with as sparsely attended as it was, especially Sunday.....sucked.

At Bayboro, they've switched to new pads with 1010 and 1515 rails paired up so there's never a wait, other than needing the middle pads because of necessary safety stand off distance. Just have to loosen the bottom bolt and turn the rail and lock it back down again.

I've decided from now on that I'll only use 8-32 screw backers for my rail buttons and source 1010 and 1515 buttons that use the #8 so I can switch on the fly as necessary.
 
This is part of the reason I am not sure I even want to bother going to Red Glare this year. Long wait to use the 1010 rails, plus only ONE 1/4" rod pad available. We had a couple rockets (Executioner, Super Big Bertha) that were still using 1/4" launch lugs, as converting them to 1010 buttons was going to be pretty challenging. Long wait, we got in like 4-5 launches each, despite being there all day Saturday. That and the launch system not being very reliable on the A pads... when you have a fail to launch, igniter didn't ignite, clips were clean and solidly attached, we had to think what the heck? We never did get either of those rockets launched, due to multiple fail to launches, and only one 1/4" pad available.

I believe there are several 1/4" rods in the box, you just have to swap out a rail for one yourself. I didn't try it at Red Glare, but I've done it several times for my son's Mean Machine because the default launch setup doesn't include any 1/4" rods.

You could also consider some 3D printed rail lugs, which are very easy to attach post-construction. I'd be happy to send you a few BT-80 conformal ones (no charge). If you're interested, send me a PM.
 
Which I do not get. We have folks trying to fly a 40 pound rocket on 1010 buttons.
I agree, it probably shouldn't be done. It's not that 1010 buttons can't handle the weight, most pads with 1010 rails can't handle that weight. Our 1010 pads are good for about 20 lbs. and after that we need to send them out to the 1515 pads.
 
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