Quicksilver

[quicksilver-wsr]

We had a successful test of Quicksilver's electric throttle yesterday. It is the first time we have run the electric linear actuator and PLC controller together to drive the Spey's throttle mechanism, and it was great to see everything moving as it should through the full range of throttle settings.

The current installation has Dexion supporting the actuator, as there's no point in committing to the pukka machined mountings which attach the actuator to the front underside edge of the engine casing until we are satisfied that everything is working exactly the way we want it to. Also, the system at the moment is activated by striking keys on a laptop, rather than pushing and pulling a lever in the cockpit, but a throttle lever will be one of the next things we add.

There are many benefits, for us, in using an electric throttle set-up rather than a mechanical system. One is that we don't have to put in an eight-foot-long mechanical linkage between the cockpit and engine, which would also have to negotiate two 90-degree corners. Instead, there is just a single strand of electrical wiring. This saves a lot of weight and complexity, yet ensures that there will be no play whatsoever anywhere in the system.

Yesterday's test took place in the workshop. We are looking forward to testing it on a running engine when the opportunity arises. We have had a mechanical system on the boat for quite some time, and that will be used for the first few static engine runs, then we will disconnect that and try out the electric version.

[quicksilver-wsr]

Yes, Mike - a good question. I've been so wrapped up in the testing that it's easy to lose touch with how these things "scan" when put down as the printed word on a forum.

We will have a lever initially. That's been the plan for quite a while. For workshop testing, and for static engine-running tests at Bruntingthorpe. Then, when we get the boat on the water in its initial form - in what we call "Dash 1" form - for trials to see how it turns and burns, and whether it can get on the plane, we will in all likelihood continue with that lever, which will be on the left side of the cockpit, as with the Buccaneer (although, for various reasons, we currently have the lever for the mechanical throttle on the right side).

I don't have a worry about having only one hand on the steering wheel at the lower speeds we'll see with Dash 1. But for the much higher speeds, with the boat upgraded to "record level" - as Dash 2 - we plan to have a foot throttle.

I was counting-up, the other day, the total number of systems on the boat - if you count the throttle as one, the steering system as another, the radio communications as another, and so on. There are 14 in all, by my reckoning. Of these, there is only one system for which no hardware currently exists, and that is the water-brake.

Thirteen out of 14 ain't bad, but there is still a lot of work to do. Some of the systems, like the electrical power-generation system, are done - finished. Others, like the telemetry system, are just starting out.

[Renegadenemo]

There are many benefits, for us, in using an electric throttle set-up rather than a mechanical system. One is that we don't have to put in an eight-foot-long mechanical linkage between the cockpit and engine, which would also have to negotiate two 90-degree corners. Instead, there is just a single strand of electrical wiring. This saves a lot of weight and complexity, yet ensures that there will be no play whatsoever anywhere in the system.

I'd have thought a control cable for an outboard would have done nicely... It's clever to design complexity, it's a damn-sight cleverer to design simplicity. (Some chief designer on the Vulcan said that)

[quicksilver-wsr]

We had that, Bill, but we weren't happy with it. We tried a Bowden-cable-operated throttle system lifted straight off a powerboat, complete with the powerboat throttle quadrant and throttle lever. We found that there was slightly more play in the system than what we need for Quicksilver, so it was turfed into a corner - with some regret, since we'd paid good money for it.

As I have said before on this thread, we don't go for complexity for complexity's sake. What's the point?

"We don't use a camera if we can use a mirror."

Visible proof of the fact that we use "simple" if "simple" works best is our current, mechanical throttle system. It uses two lengths of cable and two wheels from a baby's pushchair, taken from a rubbish tip. Yes, you read it right - pram wheels! Bright yellow plastic. And the throttle quadrant is made of wood!

Like I said, we just want the best solution to each problem, and if the solution is easy we'll go the easy route, and if we can do it better with something more complex we go the complex route.

[Renegadenemo]

Nigel, you should shop with these guys. I have for years.

http://www.ondrives.com/index.php

You could buy all the bits over the counter to build a deliciously precise linkage to go around as many corners as you like and have it built in a day.

[quicksilver-wsr]

I can see I'm not going to be able to convert you to a love of fly-by-wire any time soon, Bill, but thanks very much for the web link. That's an interesting site and there is some kit there that we may be able to use.

I'm sure that, with the right kit - as you say - it would be possible to make really good mechanical linkages, and go round corners with it and so forth. But, however you slice it, a mechanical linkage is still a mechanical linkage and we don't see the benefit of having a lot of kit to push and pull and go round corners - rockers, gears, lever-arms, push-pull rods, cables and so forth - when all we need is a length of electrical cable no thicker than that on your friendly neighbourhood Hoover and the job is done.

Yes, admittedly, there needs to be a fair amount of clever kit at either end to make a fly-by-wire system work, but - overall - the benefits in terms of weight-saving, packaging within the tight confines of the cockpit, sponson-arms and hull, and so on, mean that the work needed to put that together is well worthwhile.

Don't forget that the reason we use fly-by-wire isn't just because it's easier to go around corners and through bulkheads and suchlike. That is only one benefit. There are other benefits, such as being able to change the steering ratio - to any figure within an almost infinite range - in about two seconds flat with just the press of a button on the dashboard (no hardware changes necessary at all). Another important benefit of an almost exclusively electrical control system is that we can integrate everything so that we can cope better if an emergency situation develops at high speed. Also, for data-acquisition, fly-by-wire systems create their own data-streams and serve them up "ready-made", thereby saving us the trouble of instrumenting everything.

The (twin) rudders and water-brake on Quicksilver are 30 feet away from the cockpit. It doesn't appeal to us to create two mechanical linkages to run over all that distance when it can be done with a couple of strands of wiring.

Don't get me wrong - I'm not saying fly-by-wire is the only way to go. I'm just saying that it's the way we ended up going.

As I say, though, the link you provided shows some nice kit and I will trawl through it carefully the next time we need to add something to what we're currently building up.

At the moment, with our throttle system, our next job is to replace the rather flimsy test set-up we made with something more sturdy, so we don't get engine vibration causing oscillations in the throttle linkage and engine speed. It isn't the final design, but it's certainly been a good start to prove that it will all work!

We are going to add a throttle lever now, so we don't have to use the laptop. We can use either a 0-10v or 4-20mA input signal (we have a couple of 10cm linear potentiometers that can be used as a quick fix). To drive the linear actuator, we don't need our entire PLC controller - we can just use a potentiometer to generate the 4-20mA current signal. The PLC was expensive, so, in tests, we only use it when we need to.

[Renegadenemo]

I can see I'm not going to be able to convert you to a love of fly-by-wire any time soon, Bill, but thanks very much for the web link. That's an interesting site and there is some kit there that we may be able to use.

I think fly-by-wire is a fabulous concept and in the right hands it has been made to work but I'm damn sure I'd not want a shred of wire connecting me to something as important to my throttle unless I'd lifted the whole shebang straight from a Eurofighter then had it serviced by the OEM and delivered and fitted by qualified techies.
You may be able to infinitely vary the ratio with your computer but traditionally this is why your brain is connected to your hand (or your foot) and, as for instrumenting it, fit an encoder on the shaft and have someone with a laptop reverse engineer it from there.
This is not a criticism, Nigel, it's more an outpouring of frustration because I sometimes wonder just who fills your head with all this nonsense. We all want to see your boat on the water, God knows we do, but at this rate you're going to be stepping aboard using a Zimmer. Engines have been reliably connected to throttles with string and sticky-tape a hell of a lot further away and at stranger angles than you have in mind since the fifties and now all of a sudden it's become a challenge?
Come on - stop wasting money on boffins' private flights of fancy and build a bloody boat, will you!

Rant over.

[quicksilver-wsr]

Good rant, Bill. And some valid points made. And, just so you know I don't take offence, I'm dropping you this line to say I will respond, but can't reply today as I have a load of running around to do.

I will explain some reasons/background to what we're doing - and why we're doing things this way - tomorrow. It then may make some more sense, although it may still not fit with how you see things. But that's OK.

[quicksilver-wsr]

Mike could have been referring to me. But we don't use Meccano. We use Lego, pram wheels and left-over bits of Airfix kits and radio-controlled model cars.

[Renegadenemo]

I knew I'd not offend you, Nigel. Just want to thrash a few things around for fun. You never know, some useful ideas might shake loose.