Rail button ?

[ewallace]

Would the PML URETHANE RAIL GUIDES for standard 1010 rails work ok for a 3" min dia rocket with a 75mm 6000 M motor? rocket with motor ready to fly is 18 pounds

 

[rfjustin]

Would the PML URETHANE RAIL GUIDES for standard 1010 rails work ok for a 3" min dia rocket with a 75mm 6000 M motor?

Sure. They might be single use, but they will work.

I prefer the aluminum conformal rail guides from GiantLeap, but the PML should work as well.



Justin

 

[Daedalus]

Sure. They might be single use, but they will work.

I prefer the aluminum conformal rail guides from GiantLeap, but the PML should work as well. Justin

The aluminium rail guides running on aluminium rails are not too good as they tend to spall and damage the rail. There are clubs and individuals that will not allow aluminium guides or buttons to be used on their rails.

 

[troj]

The aluminium rail guides running on aluminium rails are not too good as they tend to spall and damage the rail. There are clubs and individuals that will not allow aluminium guides or buttons to be used on their rails.

Aluminum guides are fine, if they are perfectly aligned. The problems occur when they're not lined up properly.

Me, I prefer delrin/nylon buttons. I've seen conformals pop off, which isn't a good thing....

-Kevin

 

[Handeman]

Would the PML URETHANE RAIL GUIDES for standard 1010 rails work ok for a 3" min dia rocket with a 75mm 6000 M motor? rocket with motor ready to fly is 18 pounds

They will work, but I would highly recommend moving up to the ones for the 1515 (Extreme) rail. Not so much for the guides, but based on the motor size and rocket weight I think you should have a heavier duty pad then what most 1010 rail pads are. Most pads are sized for the rail and the pads with 1515 rail are usually much heavyer and stronger then the pads designed for 1010 rail. With the 18 lb rocket and a level 3 motor, I would highly recommend the larger rail.

 

[hognutz63]

They will work, but I would highly recommend moving up to the ones for the 1515 (Extreme) rail. Not so much for the guides, but based on the motor size and rocket weight I think you should have a heavier duty pad then what most 1010 rail pads are. Most pads are sized for the rail and the pads with 1515 rail are usually much heavyer and stronger then the pads designed for 1010 rail. With the 18 lb rocket and a level 3 motor, I would highly recommend the larger rail.

I disagree with this. I do not see any problem with using a standard 1010 rail. I have flown a 4" 31lbs. rocket off a standard rail with an M. I saw several 3 and 4 inch min diameter rockets launch off standard 1010 rails at AIRFest the beginning of this month. Why would you want to add the additional drag of large buttons to a min diameter rocket? I add another vote for the conformal launch lugs. Just makes sure to scuff the the backside up and the bodytube and JB Weld them on. Talking with members of our club, somewhere between 40 and 50 lbs is when you really need to start looking at large rail buttons.

YMMV
Eric

 

[ewallace]

The motor is most of the weight at 12.20 pounds and the rocket at under 5 pounds ready to fly. I may need to build a tower so I don't have to put any thing on the tube that will hinder the altitude

 

[als57]

Me, I prefer delrin/nylon buttons. I've seen conformals pop off, which isn't a good thing....

-Kevin

The PML guides are drilled for a couple 6-32 screws. On a G10 rocket I drill an undersize hole and thread it. Couple of screws and they are on pretty tight. Haven't had one pop off yet.

Al

 

[GaryT]

Well you know what they say about opinions, So I'll give you mine as well.

Personally I'd go with Extreme rail buttons, Yes standard buttons would work but whats the point? just cause you can???? As for drag and altitude? You wont see any! discernible difference.

 

[Bill P]

The motor is most of the weight at 12.20 pounds and the rocket at under 5 pounds ready to fly. I may need to build a tower so I don't have to put any thing on the tube that will hinder the altitude

Fred (Fade To Black) can whip you up one.

Cackle Power!!!

 

[DAllen]

Eric,

If you are going to fly that with Michiana Rocketry I can tell you that our away pad can handle 1010 rails and the pad is quite stout. It was used in the Michiana/Team1 joint launch this past April and IIRC it handled L's and M's easily. We have a really long 1010 rail which I think is at least 10' but I can check into all that if you are interested.

-Dave

 

[Handeman]

I disagree with this. I do not see any problem with using a standard 1010 rail. I have flown a 4" 31lbs. rocket off a standard rail with an M. I saw several 3 and 4 inch min diameter rockets launch off standard 1010 rails at AIRFest the beginning of this month. Why would you want to add the additional drag of large buttons to a min diameter rocket? I add another vote for the conformal launch lugs. Just makes sure to scuff the the backside up and the bodytube and JB Weld them on. Talking with members of our club, somewhere between 40 and 50 lbs is when you really need to start looking at large rail buttons.

YMMV
Eric

I don't disagree that 1010 rail can work for large rockets. It's not the rail I would be worried about, it's the pad the rail is attached to. As long as the pad itself is stout enough, you can launch almost anything off 1010 rail. I know at our club you will not be allowed to launch a M motor off a 1010 rail because we don't have any pads strong enough with 1010 rail on them.

 

[hognutz63]

I don't disagree that 1010 rail can work for large rockets. It's not the rail I would be worried about, it's the pad the rail is attached to. As long as the pad itself is stout enough, you can launch almost anything off 1010 rail. I know at our club you will not be allowed to launch a M motor off a 1010 rail because we don't have any pads strong enough with 1010 rail on them.

Your rails are not interchangeable with pads? All our HPR pads in our club can accept anything from a 3/16" to at least 1/2" rods and we have all our rails, 1010 and 1515, attached to a ~2-3 ft. length of 1/2" rod. I am looking at this as more of a performance thing though. Big buttons on a 3" min diameter rocket vs. small buttons with a big M loaded could be as much as 1,000 or more difference according to some sims I have done with RASAero.

Eric

 

[GaryT]

Big buttons on a 3" min diameter rocket vs. small buttons with a big M loaded could be as much as 1,000 or more difference according to some sims I have done with RASAero.

Eric

Sims are just that Simulations, There is no way your going to lose a 1000' off the flight due to using extreme buttons over standard.

 

[hognutz63]

Sims are just that Simulations, There is no way your going to lose a 1000' off the flight due to using extreme buttons over standard.

It depends on how extreme your flight is. If you are only flying to 10k or so it would probably make a couple hundred feet difference. If you are flying to say 30k, it could make a thousand feet difference. It could be the difference in 30,200 ft of 29,100 ft. It is a matter of magnitude.

Eric

 

[ewallace]

on a model rocket,a lug can account for as much as 35% of the "total cd "..

skin friction drag accounts for 25-30%of the total cd with lugs
and 35-45% without lugs


an example from the book "Topics in advanced model rocketry"
showed removing the lug from a certain model rocket may reduce the drag coefficient from 0.7 to about 0.45

these figures are for a typical streamlined ,well constructed model

improper construction can alter the figures drasticall

 

[cjl]

Sims are just that Simulations, There is no way your going to lose a 1000' off the flight due to using extreme buttons over standard.

On a minimum diameter rocket going to 25k at mach 2+? I'd believe that there is a significant difference. I wouldn't be at all surprised if it were a thousand feet in some cases.

 

[GaryT]

Sorry fella's IMO/Experience not gonna happen, Also lets NOT Hi-Jack this thread with a debate on CD.

 

[madmax]

Best answer is to build a tower. That is the only way to go for altitude. They are not incredibly hard to build especially if it isn't adjustable. Get yourself a bucket and some EMT or square tubing and set the rods in there with some airframe to set the diameter, secure the tubing and pour cement around it. Make a ring for the top that ties the tubing together but it has to be big enough to clear the fins. No ring is why alot of people's tower launches end up going off axis. Coat your tubing with some sort of silicone spray or if using square stuff, there are some Delrin deals that fit right over the top so the rocket glides easily through the tower. Check the web for pictures for inspiration.

Forgot to add if you are going to use a rail, I recommend the smaller 1010 series but make sure your pad is SECURE! That Loki motor is going to hammer your bird into the air fast and if not secure can move your pad. Rails may not whip but unsecured pads can flex or bounce and launch rockets way off course under power. Check out pictures of Mike Fishers M8000 in Jack Caynon's rocket. An extreme example but it kicked the pad several feet to the side and sent the bird off on about a 30 degree angle it appears.

 

[talkin Monkey]

Aluminum guides are fine, if they are perfectly aligned. The problems occur when they're not lined up properly.

Me, I prefer delrin/nylon buttons. I've seen conformals pop off, which isn't a good thing....

-Kevin

I'll second troj on absolutely PERECT alignment.

I spent A LOT of time and concentration on alignment/mounting of the large PML rail guides on my L2 rocket.

As it turned out, I still spent about 20 minutes sanding them down at the away pad in order to get a too tight fit.

I managed to cert, but I think my altimeters would have beeped out closer 2200~2500' had the rocket not had to roast its way up the rail. 1700' is what the rocket actually acheived.

As recommended by many at the launch, some rail buttons are in my future.

 

[rfjustin]

I saw several 3 and 4 inch min diameter rockets launch off standard 1010 rails at AIRFest the beginning of this month.

One of them was mine. 75mm MD, M-1315, and the rocket did have the aluminum Acme Conformal Rail Guides. I don't have a tower at this point in time, nor do I desire to transport one 750 miles to use it. That's why I chose to sacrifice some performance for simplicity.

I agree that the ACRG's do need to lined up straight on the airframe.



Justin