PeterF
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Posts posted by PeterF
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1 hour ago, Phil B said:
Looks like the industry recommends much thicker cable for these currents.
As noted above, industry ratings are for continuous operations. The other key factor is these will be ratings for PVC insulation which is typically max 85degC insulation temperature, in models we are using silicone insulation which is typically 180-200degC so we can run much higher current without the risk of insulation breakdown. I have planes with 100-110Amp through 10g wire and the wire is warm on landing 30-40degC.
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1 minute ago, Ron Gray said:
For what? (I’m interested in this as it’s coming up to club committee membership!)
For example if a member is climbing over a stile that is the clubs and the stile collapsed and the member was injured, the member would have a claim against the club and its officers. Most clubs are not limited companies where the directors are not personally liable. The BMFA insurance covers the club officers.
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Drone cover club insurance limited to below 7kg model weight and flight below 400ft. Quite restrictive. It appears it is flyer only insurance. As a club officials I am happy that I am covered by the BMFA insurance also covering me acting as club Secretary. We also get club cabin contents insurance. If you are going down non BMFA club route these are things that need to be purchased separately. Personally I would not want to be a club official without insurance in place for club officers.
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I do not agree on using throttle travel to limit the ESC. I have always understood that part throttle causes more heating of the ESC because the FETs are switching on and off when compared to full throttle. Limiting it in this way will always mean more switching for the same current than if you just put a smaller prop on.
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You just have to admire Chris Golds' extensive back catalogue of plans of unusual planes. That looks a treat.
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Flying today, in sight of the north east coast with a cool north easterly blowing in. Got the thermal gloves out for the first time.
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14 minutes ago, PatMc said:
You're example is a measure of the input, have you measured the output, i.e. rpm ?
A very valid question, if they are all the same rpm then the efficiency will be very low and that is a lot of heat for an ESC to dissipate.
A 3% difference in rpm will be a 10% difference in power given the cubic power law of fans.
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3 hours ago, Chris Walby said:
Is there any telemetry out there with the capability of measuring individual cell voltages? Ok in this case it would be 12 inputs, but it could be handy on the low cell set-ups to see if one cell is on its way out (like EDF set-ups that have high current draw)?
Jeti can do this with their MULI sensor, one sensor measures up to 6S. , They can be connected in series for higher cell packs but as far as I can make out when used for higher than 6S each sensor only does 5 cells. I have not used them for more than 6S.
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Interestingly, I have looked at Overlander 35C Supersport batteries from Overlander. 3S 2,200mAh = £21. 6S 6,250mAh = £145. If you purchased 6 of the 3S 2,200mAh packs you could form a 6S 6,600mAh battery for £126, cheaper and higher capacity than the large pack. This illustrates either (1) the economies of scale or (2) increased competition in the marketplace for the smaller batteries.
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17 hours ago, alan p said:
Hi Simon
Assuming the waxy appearance means they are blown
The waxy substance may well be a thermal paste to improve conduction of heat from the MOSFET to the heat sink.
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Walker Midgley of Sheffield do model engineering insurance for fire / theft from your workshop for both models and equipment plus transport of models. I believe they will do this for RC modelling as well.
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11 minutes ago, martin collins 1 said:
Very nice model Peter, i am just finishing off a Chris Golds KI-61 mini fun fighter, he seems to have been very prolific in his drawing of scale plans, is there a list somewhere of what is available of his designs? I enjoyed building this one and would like some more similar ones.
I believe that the description "prolific" is an understatement. I do not know if there is a single list, I have seen such a list requested on RC Groups to no avail. A lot of his stuff was in "Quiet & Electric Flight" and "RC Model World" which have ended up with Sarik Hobbies which is where I bought my plan and short kit from, but he also published plans in "Flying Scale Models" which are not available from Sarik, most notably an 84" Canberra for 2 x 90mm EDF. A lot of his prototypes ended up having posts written on RC Groups by his colleague Robert May. So you have to search around a bit.
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Shorts Sperrin from the Chris Golds plan, 74" wingspan. 4 x 55mm Vasa fans, running on 6S, 53,000rpm producing over 800g of thrust each and using 450W. Successfully maidened today. Will take off from grass runway (not bowling green smooth) but would be better of tarmac. Will happily cruise around on 150W per fan so 9 minutes flights are possible.
The Sperrin was designed late 40s early 50s as a fallback in case the Vulcan, Valiant & Victor, all revolutionary designs failed to live up to expectations. The Sperrin was very much a conventional design, rounded rectangular fuselage, basic wing with the unusual (in hindsight) stacked engines rather than side by side. 2 prototypes were built and ended up being used as test beds for other engines and for flight research.
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I printed the 3Dlabprint Stearman, the fuselage had locating tabs between sections but the wings did not. You had to use slow cyano, get them lined up in the few seconds available then give them a quick blast with kicker, a job that really needed 3 hands.
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I have used overlander lately, https://www.overlander.co.uk/, they are at the costlier end of the price range but are working well, nearly 100 flights on some packs and performance is still really good and no sign of puffing. One thing I have noticed is that for a given capacity they are smaller and about 25% lighter than Turnigy or other budget brands. Often I end up buying the same size pack and have 25% more capacity for the same weight.
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Thanks everyone.
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I have a Gloster Gladiator from a club member who has passed away and I would like to identify the kit if anybody recognises it. I have tried searching on Google but have not unearthed anything. Some pertinent details are
Wingspan 167cm = 66in which puts it at about 1:6 scale
Power 2 stroke 90
Wings built as 2 full span wings
Fuselage Fully moulded fuselage, rear section has balsa stringers glued to the outside of the fibreglass with fabric type covering over.
U/C Heavy duty piano wire soldered construction
A couple of other details are the wing retaining bolts have nylon bolts which sit inside machined inserts which sit in cups in the wings.
It needs some TLC, especially new cabane struts but it appears to be structurally sound.
Does anyone have any idea about the manufacturer.
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When you have loaded an STL file into your slicer there should be some mechanism to scale it, either right click or look for an icon. Searcg Google for your slicer. For example I run Cura, the 3rd icon down on the left like a small white cooling tower by a larger black one is the scaling function. Then you can print yoda at whatever scale you want to be your pilot.
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5 minutes ago, Paul De Tourtoulon said:
So no parachutes, plastic bombs, dropping sweets or piggy backing gliders ?.
You can drop these under the BMFA authorisation as long as you do not endanger people or property. The clause is quite clear in this respect. Outwith the BMFA authorisation, the CAA rules prohibit the dropping of articles completely.
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The BMFA Article 16 authorisation states
9. Dropping of Articles
The new regulations prohibit the dropping of any materials from a model aircraft, but our Authorisation exempts us from this requirement subject to the following condition - The remote pilot must not cause or permit any article or animal to be dropped from an unmanned aircraft so as to endanger persons or property. -
The other trouble is that the battery IR is so low that a poor connection on the balance lead can skew the results, and if it is one of the mid pins then it will give a high IR reading on two adjacent cells. It will also mean that the error is the same on both cells.
In your case were the 2 cells at 31milmohm adjacent to each other, if so could this have just been a poor connection given how different they were and it has now reverted to normal.
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6 hours ago, EarlyBird said:
Yes that's what I said so a separate UBEC is used to drive the servos.
Steve
Yes, but when I started typing my response you had only put the diagram up, so I was responding to that. At the same time as I was typing you posted about the actual function of the SPC port and that got posted before I finished typing.
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SPC port only powers up the receiver side of the board, it does not power the servo outputs, so you can not use it for the OP's purpose.
Having used the telemetry sensors, the data port is probably not on the servo power bus as the sensor stations needed their own power supply.
Yes you can Y lead together the battery and a servo, one to the tow release, the other to perhaps the throttle.
I can not comment on putting 2 heavy duty flap servos on one Y lead. Is the plane too large for a set up that is being contemplated and you should be considering one of the power box type devices where the batteries supply the power box and servos take the power from this rather than direct from the Rx.
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High current installations?
in General Electric Flight Chat
Posted
I hit a lucky point a few years ago when HobbyKing was selling off some 16,000mAh 6S 10C Lipos for just over £50 each, so I bought 6 packs, now I have a 96Ah 24V field battery that weighs less than a standard 12V 100Ah lead acid leisure battery and has much more useable capacity. OK it was 3 times the cost of the lead acid (2 times if factoring in useable capacity), but in the long run I believe it has been worth it. You could not repeat this now with the cost escalation of Lipos.