Best Rail Guides for Surface Mounting on High Velocity Rockets

[BryRocket]

Hey y'all,

I'm needing to make a decision on what rail buttons/guides to use for a 54MD rocket. I've considered using fly-away guides but have opted for permanently affixed options. I have printed my own a few times using PETG material and haven't had one fail yet but I also haven't pushed one Mach2+. I'm concerned they wouldn't survive. Does anyone have any good recommendations on such a guide that is preferably conformal, surface mounted and is durable enough for higher Mach flights? Has anyone flown PETG printed guide to high velocities? I generally attach my surface mounted guides with Proline.

 

[3stoogesrocketry]

I've machined a set of brass buttons for a 3 inch 7600 minimum diameter flight. The rocket shreaded at mach 2 ( clam shell nose cone collapsed ) but the buttons showed no sign of damage.

 

[BryRocket]

A type of metal rail guide would work good I'd assume. Do you make and sell them? I don't have any way to machine metal.

 

[mrwalsh85]

Consider the impact of metal guides on your club's equipment. Metal buttons could nick, mar, otherwise damage the rail, causing issues for other flyers. Plastic/nylon buttons are cheap compared to the cost of replacing a 12 foot stick of 1515.

 

[mikec]

I use Acme aluminum guides. If they're in good condition and aligned correctly I don't see how they could damage a rail.

 

[BMAT]

I've seen more damage to rails from sparky motors than any wear from an aluminum rail guide.

 

[3stoogesrocketry]

Consider the impact of metal guides on your club's equipment. Metal buttons could nick, mar, otherwise damage the rail, causing issues for other flyers. Plastic/nylon buttons are cheap compared to the cost of replacing a 12 foot stick of 1515.

Yellow Brass is self lubricating on a microscopic level. 6061-T6 has a Brinell hardness of 100 to 107 . Yellow Brass has a Brinell hardness of 85 to 95 . The brass will distort and get damaged before the aluminum will.

 

[rcktnut]

I have 2 1010 rails that are 15+ years old, been many Acme rail guides run thru them, they are just fine. I would say probably a good thing to run some of them thru a rail, clean all the other crap off of them. Don't know who came up with the idea that they damage the rails. If someone can say they damage the rails then I can say that using "softer" materials for guides than what the rail is will build up on the rail.

 

[BryRocket]

Alright. Thanks for the input. I ordered a set of the ACME ones. Looks like a good recommendation.

 

[SammyD]

I find the ACME guides to be awfully long for my 2", 3", and 4" rockets, so I cut them down to about 1/2" in length and bevel the leading edge (see photos). In that way they more closely resemble a rail "button" in the contact area. Why did I do that?

Moving a rocket up and down a rail by hand caused me to feel like there was too much contact area with the rail for a guide that was some 1.5" - 2" (from memory) long. Here's a photo of a 54mm diameter fiberglass kit with the ACMEs on it. The base area that attaches to the airframe is about 1/2" long while the portion that interlocks with the rail is about 1/4" to 5/16" long.

The other advantage to this is that I can get 6-8 guides out of a pair of standard ACME guides...

 

[cwbullet]

You can also 3d print Acme like rail buttons.

 

[cherokeej]

For extreme flights, there's always the tower option.

 

[Mugs914]

+100 on Acme rail guides. I do mine the same way Sammy does and have never had a problem. I think you'll like 'em.

 

[BryRocket]

You can also 3d print Acme like rail buttons.

I’ve printed a number for other projects but I was concerned about the PETG holding up in its time spent above Mach 2. Have any experience with that?

 

[BryRocket]

+100 on Acme rail guides. I do mine the same way Sammy does and have never had a problem. I think you'll like 'em.

Agree. I’m glad Sammy recommenced then.

 

[Rob702Martinez]

Full length Acme guides pinned with 3/16 steel rod sections to the airframe. Bonded with JBweld. Cut the pins to insert into airframe butted against motor tube and slightly taller then the guide. Creates a mechanical connection. Made the holes drilled very close tolerance almost having to press the pins in. They formed a nice fillet on top of the guide.

 

[Mugs914]

I do mine a little differently, but the result is similar.

I drill through the center of the rail guide (between the ears) and the tube where it will be mounted, That way the JB Weld squishes out through the holes forming a solid rivet.

To be honest, both methods are probably overkill. If the surfaces are prepped correctly the JB Weld should be plenty strong enough for anything that would use Acme guides.