Roger Simmonds

Roger Simmonds, owner of Jetex.org

Rapier Motors 2014 - a Users' Guide

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I have now tested some of the latest L-2 and L-1 motors collected from Dr Zigmund by our very own 'Nighthawk'. 

Dr Z's  nominal thrust ratings are:

70Mn for L1
130Mn for L2
150Mn for L2X
200+Mn for L2HP
 
We have, as yet, no examples of the 2014 'L-2 HP' or L-3 motors.  
 
In actual tests, and these were in duplicate or triplicate to be sure I wasn't measuring a 'one off' rogue motor, this is what I found for the motors we do have in stock:
 
L12014 thrust
 
 
Above: note the 2013 L-1 motor tested with the others.  Thrust is a bit down from when I tested these in 2013, but still very usable.
 
 
L2 2014 thrust
 
 
 
L2 X2014 thrust
 
 
 
The first thing thing to be said is that these thrusts bear little relation to dr Z's 'nominal'  ratings, and I really don't know how Dr Z arrives at his figures.  But mine are what I found, and I have the videos of the thrust rig to prove it!
 
 
 
However, the good news is that the output of the 2014 L-1 motors is healthy, a bit higher than those from 2013, but great for  profile scale models of 8-10" span.
 
The 'standard' L-2 motors are disappointing, the thrust is low, and though the run time is gratifying, the motor cases did come close to 'burning through':
 
L2 2014
 
 
They are of too low a thrust for the old 'Flying Scale' models and though suitable for profile models, I did find them difficult to light.  They needed extensive 'boring out' with a 1mm reamer and the addition of 'fairy dust' (ground up match heads) to get going.  I would advise these are used with caution.  In the right (light!) model the long burn time could give a splendid flight and a long walk!
 
I hope that when Dr Z visits in July he can bring some standard L-2's of a more useful specification.
 
 
The good news is that the 2014 'L-2X' motors are quite close to what I found for the 2013 examples:
 
L2X Blog
 
Above:  L-2 X motors tested in 2013.  This graph is included for comparison.  Ace flyers like Mike Suart found them very useful, and my larger F-100 Super Sabre liked these motors a lot!
 
 

 

Note the  shorter, though still acceptable, burn time of the 2014 motors.  The 2013 L-2X  motors worked well in built up models, and  larger profile ans semi profile models (like my F-100) and I hope these 2014 motors will be the same.

 

The less than good news is that stocks of these 2014 L-2 X's are limited - so order now.  

 

For those who want to fly Rapiers this year, and are starting out - my advice would be to buy some L-1's (of which I have good stocks ) and put it them in a (colourful) profile model (see the Jetex.org store!).

 

I hope  talk to Dr Z in July  so we can get some good L-2 motors of 120-130 mN, but until then we do have to, as in years gone by, work with what we've got!

 

As an 'addendum' to the above, here are some photos taken during the actual tests, just to prove I'm not making any of  this up!L2 test

 

Above: a standard L-2 in the middle its run.  Note the reading hovers on '11 grams'.  The weight of the motor at this point can be calculated to be about 3-4 grams.  The exhaust is barely visible.

 

L2 2014 thrust end

 

Above: a standard L-2 at  the end of its run.  Note the reading, seen through the smoke, is now '0 grams'.

 

By subtracting the weight of the motor at each time point (the motor looses about 5-7 grams during the power run ) it ca readily be calculated that the thrust of these standard L-2 motors is, at best, below 100 mN.  Note the charred motor case.

 

L-2X thrust

 

Above: an L-2 at mid run.  Note the reading hovers on '27 grams'  If the motor at this point weighs about 4 or do  grams it means the (static) thrust is over 200 mn.  

This is a useful amount of grunt, but not the 150 mN' specified.  Note the rather impressive glowing exhaust which contrasts with the more feeble exhaust of the 'standard' L-2.  The L-2 X was a lot louder, too!

 

I must emphasise that these simple static thrusts  are useful in the comparing of motors, and the thrust in a model in high speed flight will be different.

 

 

 

 

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Comments

  • Roger Simmonds
    Roger Simmonds Wednesday, 23 April 2014

    I have had a word with 'Nighthawk'. it may be Dr Zigmund has sent us 'L-2 LT' motors instead of the requested standard L2 motors. The good news is that we still have stocks of the 2013 L-2 motors.

  • Howard Metcalfe
    Howard Metcalfe Wednesday, 23 April 2014

    I found the L2 LT to be just right for my Supermarine 508 profile and I recon that they will be perfect in my Slinki so all is not lost if this year's L2's turn out to be L2 LT's instead, in which case there will definitely be a run on L2 X's. I look forward to meeting Neil at M/W if the weather eases a bit more this weekend. Thanks for compiling all these figures, very useful, hopefully Dr Z will eventually tighten up his act.
    Howard

  • Rob Mcconaghy
    Rob Mcconaghy Wednesday, 30 April 2014

    Thanks for the test results! I am surprised at the variability of thrust over the engine runs; have you ever tested Jetex engines in this fashion? A comparison would be interesting. I last ran a Jetex in 1965 or so. My memory is that the thrust was fairly even, but- that was almost 50 years ago and I may be mistaken.
    Rob

  • Guest
    Alex Sunday, 28 September 2014

    Where can I buy rapier motors in the U.S.? Are there any online retailers that sell them? How can I contact Dr. Zigmund directly so I can buy the motors from him?

  • Roger Simmonds
    Roger Simmonds Monday, 29 September 2014

    Hi Alex,
    There is no way, given the US airmail restrictions, that Rapiers can be posted to the US. Surface mail within the US may be possible.

    In the 'old days', before 9/11 and Rapiers were reclassified, Shorty's Basement in the US maintained stocks of Rapiers of all types, but no longer.

    But Dr Edward Jones of the RSI in the US is developing the 'Spadron' a Rapier analogue, and, I think, is almost ready to distribute pre-production samples.

    For the latest news about this, join Jet-Ex-Press@yahoogroups.com

    Please tell us how you get on!

  • Roger Simmonds
    Roger Simmonds Monday, 29 September 2014

    Hi Alex,

    me again. Here is a comment I posted some time ago in answer to a similar question from a guy, I think, in Australia:

    Hi Thomas,

    the short answer is 'no', and this has rather killed what could be called the previously very vibrant 'Jetex-related' flying scene in the US.

    Airmail from Europe to the US of Rapiers, which appear to be classified as explosive (they contain ammonium perchlorate) is alas verbotten even for very small batches. A real shame.

    Clandestine posting is risky. Jay Crisswell in the US has a collection of motors, but I'm not sure he posts within the US.


    Estes' black powder motors are different - Estes is a large corporation with established outlets, and black powder is viewed rather differently from AP/plastic propellants.

    But your own Dr Edward Jones is experimenting with a 'homegrown' Rapier motor with an AP or GN (guanidine nitrate) formulation.

    Please have a look at, and even join in, the forum discussion at:

    http://www.jetex.org/forum/micro-rocket-reaction-motors/21-jetex-pellet-experiments-an-nc.html

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