As part of the planned 'beta testing' phase of what is still a new product, I have retested the batches of TSP L-1 and L-2 motors we received from the estimable Piotr Tendera in September 2021.
This gave satisfactory and some interesting, if unexpected, results.
1. One surprise was that, in contrast to Rapier motors, the Tendera motors were reluctant to ignite with a 'standard' 'Cord Zap' igniter.
To light these motors, even with 'boring out' some of the propellant, the voltage needed at least 4.5V rather than the 3V or so given by two AA batteries. The 28 SWG element really needs to be glowing.. David lane's igniter (6v or so) worked well.
2. A bigger surprise, again in contrast to Rapier motors, was that TSP motors ignited reliably with just a short length of fuse, without the need for any boring out of propellant.
3.The performance of motors was entirely as expected from experiments conducted last year (below)
L-1 motors produced a little over 100 mN for 15 sec; As received, without any boring out of nozzle or propellant; September's 'TSP L-2 HP produced a powerful 300-350 mN for 16 sec; boring out the nozzle to 1.7 mm resulted in a very nice thrust of 150-170 mN for 19-21 sec.
I would add that I also tested some of the prototype TSP L-2 motors I received in the spring of last year. These gave a nice 150 mN for 25 sec. I would be happy to share these at meetings (if we have any this year!).
I was careful to test duplicates of each motor (and blow the expense!) and it has to be said that these results are more predictable and reliable than for my Rapier motors.
This is most encouraging - we can fly with the motors we now have in stock (both Terry and I have quite a lot) and we can pass these on with a clear conscience
What I'm less happy with is selling my modified 'Cord Zaps' unless I also include an adequate supply of fuses. I shall need to liaise with Piotr about fuses, and talk to David Lane about his much more potent igniter!
You will see from Terry's recent blog that the TSP motors have achieved the long saught-after CE certification, and that Piotr has some nicely packaged examples:
Piotr has provided the following specs:
These look to be a very nice product indeed (note the inclusion of fuses) and Terry and I hope to test some examples and publish the thrust/time graphs soon.
Certification is of course only the first step to legitimate retailing of motors, and we do not know how long this process will take.
But (and this is good news) we have adequate supplies of what could be called -1 'precertification' motors. These are now tested, and bagged or boxed up and available from me, so please contact me for prices and availability.
These are reliable motors and should last us at least until supplies of the new certified motors are available.
The L-1 motors are all rated at 88-96mN for 17 sec; the 'L-2' motors are more diverse, with thrusts ranging from 180mN to (gulp!) 420mn. Thrusts can of course be tuned by boring out nozzles to suit the model. We have a few L-3 motors of higher thrust too.
I'm tempted to say, "Hurry, hurry whilst stocks last".
We still have a good supply of what could be called the 'pre-certification' TSP L-1, L-2 and L-3 motors, so please contact me if you need some for the next flying season. These motors should last us at least until supplies of the new certified motors are available, but, (and to repeat myself) "Hurry, hurry whilst stocks last!"
Though Terry and I have not yet tested the new certified motors, and we will report on them as soon as we can, this interesting news appeared in an email from the Vintage model company (VMC):
so it does appear we will soon be able to buy motors 'over the counter' instead, as now, 'under the counter'.
VMC are to be applauded for this venture and I look forward to confirmation from VMC's Tim that they have motors in stock (and how much they are!).
I then had a thought: "VMC already have built-up Jetex/Rapier kits in their catalogue, but, if they really want to promote the new motors, they need a range of easier to build and fly profile models suitable for beginners.. For instance these:
modesty prevents me from saying who is responsible for these.
but all are proven designs and can go very well indeed and are a good advertisement for our hobby.
VMC are not averse to considering these profile models as a product line, they tell me, but they are very busy and with other projects. will need convincing.
So some 'lobbying' is called for. More than an email from just me! If you would like to see a range of rocket propelled profile models, please contact VMC (there is a contact email address on their website) to encourage them so that they will realise the interest out there and the potential market.
To do that now would be a good idea! I for would like to see a 'Jetex Revival' in my lifetime.
As any regular visitor to jetex.org knows, adapting the classic Jetex designs for 'one shot motors' whether Rapiers or TSP is not not too difficult. Adapting my profile models to make them good kits for VMC will not be so easy!
Many thanks to all who contacted VMC about profile models - they seem to have got the message. them. We are at very early stages of course, but it's a start!
I've this morning completed my testing of the new CE version motors.
I fired off 3 each of the 5 types that I received samples of from Piotr. And I must say the performance of each of the samples was remarkably consistent. Admittedly these are all from the same batch but this was very pleasing.
These new CE motors do have slightly wider nozzles to accomodate the green igniter fuse that is mandated for CE qualification but they lit easily with the fuse and then perormed steadily.
Here is the average performance for the 5 types tested:
L1 109mN 13.5 sec
L2 196mN 17 sec
L2HP 351mN 16 sec
L3 539mN 18 sec
L4 1178mN 17.5 sec
What is of course lacking is an exact Jetex 50 equivelant, something on the order of 139mN would be equivelant to the Jetex 50's claimed half ounce thrust. Over the next days I will explore the possibility of widening the nozzle of a production L2 to see if it is possible to reduce the average thrust and increase the duration. We have had some success with this technique in the past but we must see if this can be done while maintaining stability of thrust and not having a tube burn through.
I must say I'm looking forward now to some test flying.
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