Here is a list of all the postings Gareth Jones has made in our forums. Click on a thread name to jump to the thread.
|Thread: Mtronik 15 amp ESC|
This is going back to the very first post in the thread. Maybe its a bit late to do this now, but here goes anyway.
I ran my PT boat for quite some time with the set up as described in the first post. In my case I had two 25 amp Mtroniks controllers connected to the receiver with a Y lead. One of the controllers had the red positive wire disconnected so that the other controller was the only one to power the receiver. I had no failures of the controllers in this set up, but I did occasionally have a different problem.
Each controller was supplied from a 7.2 volt NiMh battery. The motors took a lot of current at high power settings, greater than 20 amps. As the batteries approached the 'flat' condition, using sustained high power settings would drop the battery voltage below the minimum required by the receiver and the boat could not be controlled. I resolved the problem by disconnecting both controller red wires , i.e. both BECs and ran the receiver from a separate 4.8 volt pack.
Maybe my previous post about mixers was a bit too complicated so I will summarise my feelings. From a personal point of view I would recommend a mixer in a low speed twin prop boat such as a tug or workboat where manoeuverability is important. However I would not use one in a high speed launch of lifeboat as I think the behaviour in high speed turns just looks wrong.
I have used the Mtroniks W tail mixer in a number of configurations and it has always worked as well as can be expected - as I will qualify in a minute.
I used it in an Elco PT boat in the following configurations all with Mtroniks Viper speed controllers and all with a separate 4.8 volt battery pack to supply the receiver, i.e all the BEC leads disconnected.
1. Three Speed 500 motors with all three outputs from the mixer connected to three individual speed controllers - abandoned this because the boat was too heavy and underpowered. The mixer worked fine except that when you went into a fast turn at full throttle the inner motor slowed down as expected but the outer one could not speed up as was being demanded, because the speed controller was already at full power. Hence the boat markedly slowed down and then speeded up as it came out of the turn.
At low speed the mixer worked fine.
2. Two Speed 600 motors with the centre motor output from the mixer disconnected and the other two outputs to two speed controllers. Worked fine except that the boat was still underpowered and when you went into a fast turn at full throttle the inner motor slowed down as expected but the outer one could not speed up as was being demanded because the speed controller was already at full power as in 1 above.
3. Two Speed 600 motors and a centre Speed 500 as a booster. All three mixer outputs connected to three speed controllers. However the centre controller had reverse inhibited and the neutral point set at about 80% of full forward using the setting button on the speed controller. Hence the centre motor only ran when at high power settings on the other two motors. This worked quite well but it still had the same disadvantage as 1 and 2 above. I am not sure that it is still possible to inhibit reverse on the latest Mtroniks Vipers, I have not bought one for a couple of years and I think they are now pre set with reverse operational.
4. The final configuration I continue to use is two Speed 700 motors and no mixer.
Apart from the high power issue the W tail mixer worked well, no need to set it up, just connect the correct leads to the correct receiver channels and control devices. Its a bit hit and miss which way round you connect the leads but trial and error works and you cant damage the mixer by wrongly connecting it, you just get some wierd and wonderful combinations of motor and rudder operation..
|Thread: Shemarah II|
The stiffening flanges for the rear part of the bulwarks have now been made from 1/32 ply and glued in position. The drawing does not show any of these flanges around the stern but Jim Pottinger was kind enough to lend me the photographs he took for the original article in Model Boats magazine and these show a great deal of additional useful detail. With his permission I have copied his photos and together with pictures from the internet it is possible to clarify or correct the drawings as necessary.
The vertical channel (a piece of white plastic section on the model) is used to locate a number of substantial wooden planks which close off the stern when the vessel is not deploying or recovering its fishing gear.
The next job has been to continue adding the half round reinforcing bars on the rear of the hull sides. As on the transom, a short piece of ply taped in position has been used to keep the bars parallel and spaced equally apart.
Again supplementary photos have been useful, as the position and number of the bars is not completely accurate on the drawings. I reckon that by the time I have finished I will have glued in place about 40 feet of 2.5 mm half round bar (bit of a conflict of units there, but you no doubt get the idea).
|In response to Neil's comments I perhaps need to clarify one point. It was not a guy who came up with the idea but a gal - my wife Elizabeth, who also built it. I can't say any more as there will be an article featuring more of her wild and wacky ideas in a forthcoming edition of Model Boats magazine and I have been sworn to secrecy by the editor.|
|Thread: Exciting development!|
To avoid hijacking Bob's excellent story with too much frivolity, please see the separate Mouseboat thread in the Scratch build part of the forum.
Edited By Gareth Jones on 08/11/2011 12:40:59
My wife Elizabeth has built a couple of Springer hulls and a range of interchangeable 'lids' one of which is the Mouseboat and since it seems to attract a lot of interest here is how it was done.
The hull is a standard Springer size with a coaming on which the lid locates.
The lid is built up in 3 mm liteply and the wheel is a standard hamster wheel from a pet shop.
The wheel is attached to the lid using four tieraps. The drive pulley is made from two servo drive disks with a 3 mm ply disk sandwiched between them. The pully is stuck on the side of the wheel using araldite.
The drive motor and reduction gearbox was cannibalised from one of our son's toys. A similar drive pulley was attached to the output shaft, again using araldite, A Tamiya connector is used to connect the motor to the speed controller. The wheel motor is just wired in parallel with the main propellor drive motor using a common speed controller.
A rubber band transmits the drive between the two pulleys through a slot in the lid.
The wheelhouse is made up from liteply with suitable cheese wrapper on top.
Mice were cat toys from Pets at Home, scaredy cat was from a dolls house shop.
The faster the boat goes the faster the wheel rotates. From a distance it looks quite convincing. Elizabeth was threatend with reporting to the RSPCA when sailing in Rowntrees Park in York.
Edited By Gareth Jones on 08/11/2011 12:43:10
|Thread: Exciting development!|
Just in case you are still worried Bob, here is a close up of the mouse.
|Thread: Shemarah II|
I have found a way to sucessfully shape the curved parts of the bulwarks in 1/16 ply and here's the method I used. I found it was impossible to put two bends in a piece of ply and get them spaced accurately where required. Hence the only option seemed to be to make each 90 degree bend independently and glue them on to the straight sections with butt joints.
The bulwarks are 38 mm high so I cut a piece of ply slightly wider, in my case 40 mm. and 100 mm long. The grain runs parallel to the short edge to make it easier to bend. I drew a line across the middle of the piece, dividing it into two sides, each 40 x 50 mm. This piece of ply was then boiled in a kettle for abut 15 minutes then pulled out with pliers and wrapped around a short length of dowel 15 mm diameter. The ends of the ply piece are matched together so that the corners meet accurately. This makes sure the bend will be true and there is no twist in the finished pieces. The ends are then clamped with a bulldog clip and the whole lot put back in the kettle for another 15 minutes.
The parts were left on the radiator to dry overnight and then lightly clamped in a vice and the ply cut along the line drawn across the middle. This leaves you with two pieces, one end with a neat 90 degree bend, the other with a slightly reflex curve.
If necessary put the 90 degree bend end in a vice and gently bend it so that the end face is true to the rest of the main part of the bend to be used. Then trim off the end with the reflex bend so you have a short straight section about 20 mm long on one side of the 90 degree bend. Clamp this to the side of a wooden block and glue on the next section of straight bulwark using superglue. A piece of newspaper underneath stops the whole thing sticking to your bench.
You can then sand the joint smooth and if necessary apply a bit more glue or filler if you can still feel the joint. Repeat this process for the next bend and the bulwarks are built up accurately and square. Finally sand off the surplus height of the bends so that the whole length sits flat on the deck. Using the 15 mm diameter dowel I ended up with curved sections which were around 10 mm radius.
This method works quite well and the superglued butt joints are quite strong. Here is the finished section on one side, still to be glued on to the hull and the vertical stiffners added. Although 1/16 ply is thicker than true scale, when the capping rail is fitted the edge will be hidden so it wont show up on the finished model.
|Thread: Exciting development!|
Just for Phil's benefit, the wheel does go round, its driven by a small geared motor cannibalised from one of our sons old toys. The motor is run in parallel with the propeller drive motor via the same speed controller, the faster the boat goes the faster the wheel goes round. The mouse's tail catches in the treads of the wheel as it rotates and looks just like its running. If you select reverse, the wheel changes direction of rotation and by a brilliant stroke of design (luck) the mouse (usually) turns round and runs in the opposite direction.
Right now you can go back to the serious stuff......
|Thread: Shemarah II|
Thank you for that Dave, I know that a Servomorph normally controls the speed of the servo to the same value in both directions, but I just wondered if there was some clever way of making one slower than the other. No point in buying another Servomorph then.
For the anchor winch I am planning to use a Hitec HS785HB sail winch servo. Its a drum type which will give me about 450 mm of travel. I will control it from the flap switch on my transmitter. That is a rotary potentiometer type and I can, to some degree at least, control the speed manually so that it drops quickly but comes up slowly. I might have to modify the drum as 450 mm of chain will take up a lot more room than 450 mm of braided cord.
I have found Servomorphs quite useful for controlling the sail winches on a couple of my wife's yachts. In that case they have not been used to control the speed but have been used to control the range of movement and end points of the sail sheets and work really well in that application. Much better than trying to limit the travel of your transmitter stick by some mechanical stop.
|Thread: Exciting development!|
Talking of hamster wheels you may be interested in my wife's Mouseboat
|Thread: Shemarah II|
I have completed the shelf for the electrical installation forward of the wheelhouse, as you can see from the photo below. This shelf slides in to a pair of channel sections leaving the centre area free to access the removable ballast and battery.
The receiver and speed controller are mounted high up on either side of the frame above the shelf. On the shelf is a 12 way terminal block which will act as a busbar and junction block. The battery leads will split at this block to give 4 separate circuits motor/receiver, sound system, lights/radar antenna motor and water pump. Each circuit has its own fuse and switch in a hatch just foward of the wheel house. The wiring for the lights on the mast will also go via the terminal block. On the real vessel this is a large hinged hatch where the catch is offloaded but on the model it will simply lift off in one piece for ease of access.
The switches and fuses are from Maplins but the terminal block has led a very long and exciting life in its past application. It was originally part of the intrumentation system in XK527, a Buccaneer low level strike aircraft that first flew in 1961. This was a development aircraft which spent its whole life on flight trials including hot weather trials in Malta and Libya, carrier trials on Ark Royal and USS Lexington, engine development and performance tests and weapons delivery testsing. It was retired from flying in the mid 1980's and cannibalised to build a ground rig for research and development of computer controlled fuel and hydraulic systems. I was the engineering manager of that final project and aquired lots of usefull bits when the aircraft was scrapped (all quite legitimately with authorised scrap notes.) I think I have enough terminal blocks to last the rest of my modelling life, unless I build something really huge and complicated like an aircraft carrier. However I can tell any interested viewers of Shemarah that at least one part of her went to sea for the first time about 45 years ago, has been up to 48,000 ft and has flown at 580 knots below 100 ft..
Edited By Gareth Jones on 05/11/2011 13:58:34
In the last week or so I have made a bit more progress with the deck and electrics. The rear part of the deck has been covered in 1.5 mm ply with a section removable over the rudder servo. I have started on the bulwarks around this part of the hull but the first attempt at the rear corners was not very good. These have a fairly small radius of around 8 mm so I am going to have a second attempt but this time steam some 1.5 mm ply to achieve the shape.
|Thread: Viper 15 Amp ESC No Reverse|
The older MTroniks speed controllers had programmable reverse and brake functions and it is possible to inhibit reverse completely. It is possible to change the programming accidentally if you press the speed controller set up button while its powered up. Have you tried going through the full set up procedure including these functions as well as the normal full forward and reverse set up, if not I can sent you the instructions to do it.
If you have already tried the full set up procedure I suggest you try returning it to MTroniks with a polite letter giving them the facts and asking them to check it out. I have had several units fail and they have replaced them all without question and been very helpful in answering any questions I have had.
Regards and good luck
Can you be a bit more specific as to which Speed 600 motor is fitted? There are lots of different variations on the same basic 600 size, some are optimised to run at high rpm and are not really suited to direct drives for boat propellers. It would help if you could quote the Graupner part number then we can identify the performance characteristics of this particular motor.
Almost certainly the propeller is too large for the motor being used, but I have not operated this particular model so I am not sure whether it would be best to change the motor or prop.
|Thread: Shemarah II|
I have spent most of my budget on a noisy thing system, I cant afford much else. I did look at the micropump website over the weekend but I can't justify that much money, even though they do look really neat little pumps.
I am still eagerly awaiting an answer to my question on page 6 of this thread (although I do apologise for spelling your name incorrectly.) Is there any way you can slow down a servo in only one direction, eg by using a Servomorph somehow?
I think my original pump gives enough flow when operating at 7.2 volts. I am not trying to simulate a jet of water from the side of the hull, just a gushing flow as shown in the photo of the real thing below. The problem is getting the white turbulent look - or maybe I am getting a bit obsessive now! Maybe I will add a bit of white paint with the odd bit of silver just below the outlets to add to the effect
I have tried another pump today in the form of a Graupner 10 volt centrifugal pump. On paper it should produce about twice the flow but in reality I dont think there is much difference at the same voltage. Maybe the pressure delivered is lower than the original gear pump but it does have the advantage that it is much quieter. However after leaving it running for around 10 minutes at 7.2 volts it was getting pretty hot and, while the Graupner instructions don't mention it, the Cornwall Model Boats website says its not recommended for continuous running. I think I will try the Graupner pump for the time being and just switch if off after a few minutes.
I have got a flow control device on one of the lines to the outlet in the stbd side. Its one of the clamp on restrictors from an old smoke system and seems to work OK by squashing the plastic pipe to a controlled degree. A reservoir might help a bit but the flow is smooth and steady now and it would only add yet more complication so I dont think I will bother.
The first tests on the simulated overboard water flows were very disappointing. At 12 volts, the pump motor was very noisy and I only got a flow from one of the outlets on the port side, nothing significant from the other 2 on that side or the one on the stbd side, see photo below.
I tried adjusting the pipe layout to get a better balance of pressure drops to even up the flow but it was still not very good. I then replaced the piping with some silicone tubing from an old fish tank. This was slightly bigger bore and gave much better performance. The picture below shows the flows from the port side with the pump motor running on 7.2 volts and much quieter operation. Unfortunately the water does not scale very well and it looks a bit more 'glassy' than the real thing.
The flow from the stbd side was comparable to the left hand outlet above so its seems reasonably well balanced and is ready for the piping to be tidied up. Heres a view of the final pipe layout before clipping. The pump is laid on its side just to give a clearer view.
I have also slightly modified the lifting handle. At the front end I have added a collar to act as a stop and a hole for a pin in front of the frame to prevent the handle sliding backwards and forwards when lifting the hull. The pin will be accessible through the hatch immediately in front of the wheelhouse.
Edited By Gareth Jones on 17/10/2011 19:04:59
Ah but, ah but, ah but, I thought about that right from the start and fitted a Raboesch propshaft with a sealed bearing!
Edited By Gareth Jones on 12/10/2011 18:29:08
The water system is purely for effect. If I had a leaky boat it would really annoy me. I suppose I could use the water flow to cool the motor but if you have to resort to water cooling on a boat like this it would really be an admission of failure.
Want the latest issue of Model Boats? Use our magazine locator link to find your nearest stockist!
Make sure you never miss out on the latest news, product reviews and competitions with our free RSS feed
We welcome well written contributions from Website members on almost any aspect of Model Boating with a particular emphasis on practical hints, tips, experience and builds.
In order to maintain a consistent standard and format, all suggestions should first be sent to me by Personal Message for approval in principle. Only a very limited amount of time is available for editing contributions into a suitable format for placing on the website so it is important that the material is well presented, lucid and free from obvious spelling errors. I think it goes without saying that contributions should be illustrated by appropriate photos. I shall be happy to give advice on this.
The Member Contribution area offers space for short informative mini articles which would not normally find a place in Model Boats magazine. It is an opportunity for Website Members to freely share their expertise and experience but I am afraid that virtue is its own reward as there is no budget to offer more material recompense!
I look forward to receiving your suggestions.
Colin Bishop - Website Editor