PML Linear launch lugs

[Reed Goodwin]

Does anyone have any experience with these? Do you run into any problems with alignment and binding? The seem like an excellent (albeit pricey) alternative to traditional railbuttons with the ability to have a very strong attachment to the rocket.
Thanks,
Reed

 

[Gillard]

i have not used them myself, but i know someone who has and really rates them. alignment is the only problem, so take your time.

 

[bobkrech]

Does anyone have any experience with these? Do you run into any problems with alignment and binding? The seem like an excellent (albeit pricey) alternative to traditional railbuttons with the ability to have a very strong attachment to the rocket.
Thanks,
Reed

The advantage of rail buttons is that they are self-aligning and simple to install where as linear guides are expensive, require precise, time consuming alignment.

• What leads to believe that you need a "stronger" attachment to a rail than rail buttons?
• How much strength do you need?
• How strong are rail buttons?
• How strong are the linear alternatives?
• If the linear alternative has "extra strength", it it indeed necessary?

Bob

 

[dixontj93060]

Linear lugs are a good choice for high thrust, minimum diameter designs.

 

[Scott Evil]

Reed,

I used the linear rail guides for both my L1 and L2 flights on Crapien 1 and 2. Both were QT Endeavour mods.

Crapien 1 with the 1010 guides epoxied and screwed into the quantum tube slightly crunched/separated the lower guide as I put it on the rail. My fault as I painted the rail guide, tried to cram it on a dirty and had the L1 jitters to boot.

Crapien 2...Was done with the 1515 rail guides (non-painted), screwed to 3" tapped aluminum conduit under the QT, aligned with an aluminum strait edge and triangulated by a distant post big bang quasar...

1st shameless pic is us waiting for some launches and get back to the car for some sandpaper to git downright mid-evil on the guides. 2nd pic is after about a 1/2 hour of gitting downright mid-evil on the guides. It still went on little tight, it kinda "posed" for a bit on the rail going up.

Moral of the story, great product IMHO but check your alignment with a hunk of rail if you can. ( I also wonder if temp changes/tweaks in the QT might be an issue in my case).

 

[Reed Goodwin]

The advantage of rail buttons is that they are self-aligning and simple to install where as linear guides are expensive, require precise, time consuming alignment.

• What leads to believe that you need a "stronger" attachment to a rail than rail buttons?
• How much strength do you need?
• How strong are rail buttons?
• How strong are the linear alternatives?
• If the linear alternative has "extra strength", it it indeed necessary?

Bob

Yeah, I like that rail buttons are self-aligning, I'm just concerned about the size of the rocket as I've never dealt with anything this big. The Linear lugs provide more surface area for epoxy to grip and two screws per lug, hence my assumption that they'd be stronger. I'm working on a 5" diameter, 10ft long, ~30lb rocket. I figure if I went with regular rail buttons, I'm gonna need the big ones (for the rocket size and the fact that I'm gonna want a long rail), but they're out of stock at railbuttons.com so I'm a little concerned about being able to find some.
Thanks,
Reed

 

[new2hpr]

Just like with the Acme rail guides, use a spare chunk of 1010 rail to align them before permanently mounting. Make sure the rail and the guides are securely taped in place while the adhesive sets, as they may sag during cure (don't ask how I know this). After adhesive is set, you can do mechanical mounting as well (screws) with the PML guides. Definitely tack them in place with CA first, so you can confirm the alignment before any drilling.

-Ken

 

[mikec]

I'm working on a 5" diameter, 10ft long, ~30lb rocket. I figure if I went with regular rail buttons, I'm gonna need the big ones...

Well, I'm not sure you really need them, but if you do LOC has them:

https://shop.rocketsbymelissa.com/category.sc?categoryId=22

If you use the PML guides (and I wouldn't, if glued on they break off with depressing regularity) then make sure to align them with a rail when you glue them on -- they are very hard to line up without a rail.

 

[Reed Goodwin]

Ah, thanks for that link! I didn't realize LOC carried them.
Reed

 

[als57]

I've used the PML rail guides on a number of rockets now. Mostly G10 and Quantum tubes.

I actually drill and tap holes in the tube and use 6-32x1/2" flat head SS screws to mount them. No epoxy or CA needed.

On cardboard tubes I've been using a t-nut for a backer. Do basically the same thing when using rail buttons.


Al

 

[slogfilet]

How long would a linear rail lug need to be for just ONE lug to be sufficient?

As along as the lug was long enough to prevent torque forces from tilting the rocket from vertical (and from forcibly removing the lug) it seems that 1 lug could suffice.

This would be understandably rocket-dependent, of course...

EDIT: The more I think about it, the less I like it... the single lug would need to be relatively close to the CG, thus reducing the effective length of the rail. Unless this was a loooong lug...

 

[blackjack2564]

Yeah, I like that rail buttons are self-aligning, I'm just concerned about the size of the rocket as I've never dealt with anything this big. The Linear lugs provide more surface area for epoxy to grip and two screws per lug, hence my assumption that they'd be stronger. I'm working on a 5" diameter, 10ft long, ~30lb rocket. I figure if I went with regular rail buttons, I'm gonna need the big ones (for the rocket size and the fact that I'm gonna want a long rail), but they're out of stock at railbuttons.com so I'm a little concerned about being able to find some.
Thanks,
Reed

1010 buttons are rated to 70lbs.

I have flown 6in. 11ft long, 45lb projects with L central and 3 J's on the outside without any problems. And this with just mounting to the airframe.

If worried you can always move up to1515 size.

 

[Reed Goodwin]

Jim,
That is very reassuring, thank you!
Reed

 

[JAL3]

I am not an expert with the big stuff and only have a few builds to my credit but I have been using the PML lugs exclusively on my bigger projects for the last year. I like them and have never had a problem. I don't have a reason for using them other than I liked the look.

 

[barstoolmike]

I've used the PML guides & found they bind pretty bad on the Black sky rails, but work fine on the 1010 rails from 80-20.

Mike

 

[blackjack2564]

Yeah, I like that rail buttons are self-aligning, ..................... I'm a little concerned about being able to find some.
Thanks,
Reed

Wildman has hundred's of them in stock right now. 5.00 for 2sets of 1010 and 5.00 for 1 set of 1515, with screws.
These are the good ones....one piece delrin. Not the 3 piece per button type.

 

[H_Rocket]

I like them and have never had a problem. I don't have a reason for using them other than I liked the look.

What he said. They just look like the shoe on a real rocket.

 

[troj]

The PML Linear guides are very nice, if you use screws to hold them. They don't go anywhere.

The trick of alignment is to use a straight-edge of some sort. Even for regular buttons, I'd suggest it, as you can get one button tilted off-axis, and have problems with them binding. I've seen it happen, fortunately not on my rocket.

-Kevin

 

[als57]

The PML Linear guides are very nice, if you use screws to hold them. They don't go anywhere.

The trick of alignment is to use a straight-edge of some sort. Even for regular buttons, I'd suggest it, as you can get one button tilted off-axis, and have problems with them binding. I've seen it happen, fortunately not on my rocket.

-Kevin

A 3 foot piece of 1" aluminum L from the local Lowes (or other hardware purveyor) makes a nice straight edge for this.

Al

 

[Boosterdude]

I used the Acme Linear lugs on my Patriot. No issues so far, and I like the look over the rail buttons. Aligning is as easy as anything else, non issue.