TOPIC: New Motors from TSP Modelar

I have now had a chance to put the 'CE' TSP L-1, L-2 and L-2 HP motors on the test rig. Most measurents were done in duplicate just to check the first run. I estimated the usable 'burn time by the sound the motor made, waiting for the moment I would actually launch a model on the flying field. Here are my results:

L-1 133 +- 13 mN 10 sec
L-2 183 +- 17 mN 12 sec
L-2HP 335 +- 33 mN 12 sec

These results are not too dissimilar to Terry's results (but note the 'burn times' which are, I admit, somwhat subjective and shorter than Terry's) . My L-1's appear a bit more powerful than Terry's. Though this is pleasing (this thrust is just perfect for my profile F-100 Super sabre) I wondered what the effect of boring out the nozzle from 2mm to 2.5mm, to (hopefully) make these TSP L-1s sutable for, say, a Jetex Wren. This gave

L- 1 (2.5mm nozzle 1) 120 +- 22 mN 12 sec.

This was 'interesting', so I tried a TSP L-2 with a 2.5mm nozzle:

L-2 (2.5mm nozzle) 133 +- 17.5 mN 14 sec.

Such a performance is perfect for some of the classic Jetex scale designs, and I look forward to Terry's more comprehensive 'boring out' experiments.

General observations:
The run times are distinctly shorter than we have got used to with Rapiers and Piotr's 'pre CE' motors. This is an inevitable consequence of a larger nozzle diameter resulting in of a lower Specific Impulse. This we can live with - there will be no more wretched 'burn throughs' - and (a) it will keep our models in smaller flying fields and away from trees etc and (b) us old guys will have less far to walk to retrieve models

Another consequence of the lager nozzles is a rather fiercer exhaust flame:



Above: a TSP CE motor on song. It was a dull on the day of the tests and the exhaust flame is bright. Hmmm ... We may find ourselves changing our motor trough linings and thrust tabs more often with these motors!

Motors did not always ignite using just a fuse: some abraision of the propellant with a 1mm screwdriver helped a lot. Ignition using a modified Cord Zap with four AA batteries worked every time.

As Terry has noted, the consistency of the motors during a run and the repeatability of examples (note the acceptable standard deviations) was good and far better than we have seen with Rapiers.

I'm looking forward to trying these motors on the flying field. I shall be soon writing an article for' Aeromodeller' about all these exciting developments - new motors, reliable distribution, new suitable models from both VMC and Piotr Tendera to suite these motors, progress with igniters. So, if you want me to include your own comments and observations in said article, start posting!

Here are the graphs of the measurements I made last week. Just to be clear, these are for each of the new CE standard Tendera motors, namely:
L1, L2, L2HP, L3 and L4. I did three runs of each type and as you will see the performance for motors is pretty consistent.


As a slight difference from previous published graphs the graph starts at the first second after the start of thrust AND a full second has elapsed. In each case I set the test rig ready, light the new green fuse and let the rig measure the data. The data gets sent to my lapbook so I can capture it and save it in a spreadsheet. The graphs are then drawn, automatically, by the spreadsheet. The rig is calibrated by turning it through 90 degrees so that a (known) hanging weight deflects the strain guage in the same sense that the measured thrust does.

In the next days I'll try and make some measurements of L2s that I've modified for a wider nozzle diameter. (2.1mm, 2,2mm etc) I'm looking forward to seeing how the L2 behaves with such a modification.

The latest email from the Vintage Model Company had this:


they can now be ordered and delivered by courier:



This is all to the good, and VMC are to be applauded for this venture which is (for them) into unknown territory.
It is unfortunate then, that they spoil it with this comment:
"They are (in our humble opinion) quite expensive. We've cut the recommended price as low as we can and I think we're cheaper than our European counterparts, but any lower and we wouldn't make any money."

I got quite fed up with these sorts of comments, then about Rapier motors, at meetings. especially as they tended to be made by guys as the got into their Range Rovers, on the back of which was a sticker proclaiming the driver belonged to a posh golf club!
That our motors are expensive is a judgement, not an objective fact. Expensive in relation to what?
When you consider all the research that has gone into these motors, the background expertise, the extensive testing and the cost of certification, these motors represent excellent value.

Yes, they do cost more than Rapiers, but TSP motors come in nice packets that give pride of ownership and I trust them more than Rapiers.

If you want to fly rocket planes, with all their attendant thrills and frustrations today then there are two options:
(a) TSP motors
(b) genuine Jetex.

I do both, usually sourcing Jetex stuff from eBay. I know which is the cheaper (and less frustrating) option!

Rant over.

Actually, flying rocket planes can get quite expensive, here's why.

Way back when we were flying Rapier planes at Taft, we would go through many motors in a day. After a flight it was a simple matter to change out the used motor for a new one, light it off and make another flight. Most of our models had sheet balsa wings, or were scale replicas, the glide wasn't the best so we didn't have far to walk to retrieve. One could easily fly a dozen flights in an hour, or until the supply of rocket motors ran out..
Here's hoping someone can find a way to import the new motors into the USA. I will be first in line to buy some.

John in Prescott, Arizona

Roger adds:

Great to hear from you John, and you are right about getting through a lot of motors in a day! A good session with Rapiers could easily put you back 60 pounds or so. But it is a lot of fun and still cheapr than, say golf or fly fishing

You could contact Bernard Guest This email address is being protected from spambots. You need JavaScript enabled to view it. importing TSP motors into the US. There surely (don't call me Shirley) must be a way.

Here are some test runs I made today with L2s modified with incremental nozzle sizes.

The 2.4mm nozzle hits the sweet spot of 139mN for 18 seconds. (Or, 1/2 oz of thrust if, like Darth Vader, you prefer Imperial measure. ) That is the notional rating of a Jetex 50 anyways.

But I was seeing some burn throughs. I'm going to try again soon with several motors modified to 2.4mm and see what happens.

Oops, I've now been advised by Piotr that the nozzle starting size is 2.2mm so my first three plots can be ignored! The nozzles are effectively unmodified.

So here's another plot with the unmodified traces removed.



And I'll do a few more tests with several motors with 2.4mm nozzles.

Roger adds: I measured the noxxle diameters of my CE TSP L-2 motors with a micrometer. The range was 2.08-2.11, say average of 2.1 mm. This would explain why your trace for '2.2mm' is a bit down on the unmodified motor and 2.3mm looks 'just right.

The consistency is impressive!

Did the motor casing actually burn through completely in a way that would endanger a model?