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Old Aug 03, 2012, 04:17 AM
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check your retracts

Figured out why BECs on my stock ESCs burned down. Apparently landing gear manages to almost shortcut the circuit at the end position. BEC draws 4.8A from 12V battery for about 0.5 sec. It happens maybe one in 20 times with gear facing down.
Seems the quality of these worm retracts went down recently. I also got a replacement metal gear from HK for MIG29 and was surprised it behaved erratically. After switching to 8A bec from 2A everything worked fine.
I have a suspicion that although they consume ~0.2A during operation (each) startup/end currents are well above 5A and may last up to 0.5sec.
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Old Aug 03, 2012, 04:52 AM
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Here's the Specs on the PZ15090. The gear ratio differs but the rest is supposed to be the same.

1. 使 用 環 境 條 件
Apply Environmental Condition:
No. Item Specification
1-1 保存溫度
Storage Temperature Range
-20℃〜60℃
1-2 操作溫度
Operating Temperature Range
-10℃〜50℃
1-3 操作電壓
Operating Voltage Range
4.8V〜6.0V
2. 測 試 環 境
Standard Test Environment:
2-1 測試環境
Standard Test Environment
每一个检查必须是正常的温度和湿度进行测量,温
度25 ± 5℃,相对湿度65 ± 10%,在按照本规范的
标准测试条件下判断特征。Every test under
normal temperature and
humidity(temperature:25 ± 5℃, relative
humidity: 65 ± 10%), and characteristics are
determined under the condition of standard
test.
3. 外 觀 檢 查
Appearance Inspection:
No. Item Specification
3-1 外觀尺寸
Outline Drawing
尺寸见附件See the appendix
3-2 外觀
Appearance
无损坏,不允许影响功能No damage and mustn’t
affect functions.
Product Name
中型起落架
Model No.
PZ-15090
Version
V1
Page
1/3
文件编号:PZ15090-RD-01PS
4. 電 氣 特 性
Electrical Specification (Function of the Performance):
No. Item 4.8V 6V
4-1 空載轉速
Operating speed (at no load)
0.7±0.1sec/90° 0.55±0.1sec/90°
4-2 空載電流
Running current (at no load)
120±30mA 130±30mA
4-3 停止扭力
Stall torque (at locked)
1.8±0.1kg-cm 2±0.1kg-cm
4-4 停止電流
Stall current (at locked)
900±30mA 1000±30mA
4-5 待機電流
Idle current (at stopped)
3±1mA 3±1mA
4-6 空載寿命
Running life(at no load) >10000 次 >8000 次
注:项目4-2 定义平均值时,伺服器无负荷运行
5. 機 械 特 性
Mechanical Specification:
No. Item Specification
5-1 外觀尺寸
Overall Dimensions
见图纸See drawings
5-2 機構極限角度
Limit angle
90°
5-3 重量
Weight
32±1 grams (without servo horn)
5-4 導線規格
Connector wire gauge
#30 PVC
5-5 導線長度
Connector wire length
100 ± 5 mm
5-6 減速比
Reduction ratio
1/7.72
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Old Aug 03, 2012, 09:33 AM
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end stop protection for the main retracts

Hi,
i make a simple and easy end stop protection for the main retracts.
I think it could help an gras...
I use also the "eufi" struts.
Hope to maiden in the next weeks...

Reg, George
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Old Aug 03, 2012, 09:52 AM
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That sort of looks like a good (enough) solution....
But if that is balsa (and it looks like it is) I don't think it is going to last long term. Maybe not even short term..... like 3 landings and it will be compressed to be useless anyway.
Though you are on to a good start of an idea......

Better would be hardwood, but with a rubber surface to the oleo.
Because the retracts have slop in ALL directions, you really want to make an elongated "U" that the oleo 'parks' into. So that the total diameter of the oleo is inside that "U".
And the whole inner face of the "U" is rubber. Something like using a strip of car tire tube - or two layers. About 2mm of "medium hard" rubber would be good - to allow its compression and thus absorb the energy.

You don't want a solid block against the oleo... but at worst that would still be a passable soution too. Rubber faced (that 2mm) would just be better.

But that is a great idea as a basis!!!
I totally forgot about mine, seeing a spring system was not really viable there, plus I moved to a road runway. But now seeing that idea, it would be a very simple and quick job to make up the "U"/rubber item to go in there!!

Nice lateral thinking!!! I must have been thinking vertically (and then gave up)..... hehe
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Old Aug 03, 2012, 10:12 AM
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SU 35 shutdown

Hi this is my first time on RC Groups. I fly Heli's mostly. but i bought the SU-35 as a change of pace. I have some questions i was hoping i could get some help with.

I have a stock plane 3D with vector. I have flown it about 15 times with no problems. yesterday i went out flying and it was hot out, about 100Deg. about 3 min into the flight it starts loosing power. I had put the gear down and i noticed the power dropping, i was comming arround for a landing and it just keep loosing power at the last moment i came out of the bank and flattened it out just in time to land. not where i wanted to land but it was on the ground and no damage, so that was cool. I may not get lucky again.

First are the ESC's junk (55amp stock esc) I do have a Castle BEC Pro i can put in this, a little overkill but i already have one i'm not using. but should i replace the stock ESC's or was it just the heat? Fly on a cooler day?

Any advice would be great. I started to read through this form but ran out of time and did not see anything that would help.
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Old Aug 03, 2012, 10:16 AM
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Hi Peter,

the wood near the strut is hardwood with only a c-shape and no rubber.
The wood behind is balsa, so i can control after a few landings how much stress come to this peace... Thats the the reason why i dont use hardwood on both places.

Reg, George
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Old Aug 03, 2012, 01:02 PM
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Quote:
Originally Posted by GeorgeStyriaII View Post
Hi Peter,

the wood near the strut is hardwood with only a c-shape and no rubber.
The wood behind is balsa, so i can control after a few landings how much stress come to this peace... Thats the the reason why i dont use hardwood on both places.

Reg, George
You're on the right track but hardwood even has limited endurance. Both trunnion and housing are of hardened nylon that is harder than the ply. I even get ware with the metal trunnion as it all get loose. So you may have the same effect of it waring a groove and getting loose.
RCL adapted a metal plate for mounting their version of the PZ15090. They should be a direct fit come to think of it. And I have a binch sitting around so that's for the inspiration.

The SU is made of foam but the bump you see on the full scale where the main strut meets the side of the outer duct wall is additional support for the gear. Either that or you can add the angle tension arm. Trouble is hogging out space for it to recess and somewhere to anchor the other end to.
Good idea none the less.

Wish they would just size up to the 15091Ms. Or better yet be the first to make a scale 50*/50* strut mount actuated by a 15094.... but then thats just dreaming.... or is it
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Old Aug 03, 2012, 01:16 PM
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Originally Posted by JTAnimal View Post
..., about 100Deg. about 3 min into the flight it starts loosing power. I had put the gear down and i noticed the power dropping, i was comming arround for a landing and it just keep loosing power at the last moment.....
Most ESC's do have a heat limiter that can engage the cutout setting. If you are boarder line on amps, more gets lost to heat and the performance goes down. Thus e.g. HET sets come with a 70amp ESC instead of the 45amp because many HET models don't mount the ESC in the duct only allowing for out of fuse cooling. To make certain the ESC didn't trip out they upped the ESC. For this reason I don't fly batteries back to back on the hotter days. I let the ESC's and motor cool down a bit between flights so you don't demag or over heat the drive train.

Having said all that, no idea if it all applies to these ESC's. Guess is it probably does given that when we ask for tome instructions for the ESC's they can't give us the specifics but what they do give in manuals also shows the thermal cutout protection. So maybe what you experienced.

That's also an assumption because you would know otherwise as you recharged the batteries and checked the wiring for any faults.
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Old Aug 03, 2012, 01:48 PM
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Quote:
Originally Posted by Maxthrottle View Post
Here's the Specs on the PZ15090. The gear ratio differs but the rest is supposed to be the same.

Stall current (at locked)
900±30mA 1000±30mA
I have several of them from an early batch when these devices just appeared. They work really smooth and without problems on a 2A BEC. It's the latest releases that I find strange. (f.ex. you often need to cylce them after power up to syncronize).
There are end point contacts that are supposed to switch off motor without any overcurrent. I have a feeling they are of a poor quality now and shutoff often happens by overcurrent protection instead. If 2 or 3 of them decide to do it simultaneously you get 10-15A draw for 0.3-0.5 sec.
FW retracts are of even worse tolerance that HK. If they have a 1mm play what would you expect from the contacts indide...
From now on I'll operate retracts only in leveled slightly accending flight in case of blackout.
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Old Aug 03, 2012, 02:35 PM
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Originally Posted by Sockrat View Post
I have several of them from an early batch when these devices just appeared. They work really smooth and without problems on a 2A BEC. It's the latest releases that I find strange. (f.ex. you often need to cylce them after power up to syncronize).
There are end point contacts that are supposed to switch off motor without any overcurrent. I have a feeling they are of a poor quality now and shutoff often happens by overcurrent protection instead. If 2 or 3 of them decide to do it simultaneously you get 10-15A draw for 0.3-0.5 sec.
FW retracts are of even worse tolerance that HK. If they have a 1mm play what would you expect from the contacts indide...
From now on I'll operate retracts only in leveled slightly accending flight in case of blackout.
Its one of the reasons why 6V comes in handy. When I used them at 4.8V especially with slowers or sequencers, they would alter the usec or % travel point to engage transition such that they would get further out of sink. Upped the voltage and it happened less.

But you are absolutely right, which is why in some of the electric retract threads, those who set their gear to aways stall in the retracted position, I cautioned them because about their setups and the stall amps available from their BECs and the RX brown out levels. When they crashed the kept insisting it was something else because when the metered their setups in transition they didn't always see high enough amp draws to indicate a concern. But then they are using cheap watt meters that just didn't seem to detect the manufacturers posted stall amps.

So ya I figure on the hot summer days with some of the internal BECs and very hot ESC may have lead to past unexplained brown outs on takeoff and landings around the time of the gear cycle. Hasn't happened to me yet but who knows.
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Old Aug 03, 2012, 02:46 PM
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Quote:
Originally Posted by Maxthrottle View Post
Most ESC's do have a heat limiter that can engage the cutout setting. If you are boarder line on amps, more gets lost to heat and the performance goes down. Thus e.g. HET sets come with a 70amp ESC instead of the 45amp because many HET models don't mount the ESC in the duct only allowing for out of fuse cooling. To make certain the ESC didn't trip out they upped the ESC. For this reason I don't fly batteries back to back on the hotter days. I let the ESC's and motor cool down a bit between flights so you don't demag or over heat the drive train.

Having said all that, no idea if it all applies to these ESC's. Guess is it probably does given that when we ask for tome instructions for the ESC's they can't give us the specifics but what they do give in manuals also shows the thermal cutout protection. So maybe what you experienced.

That's also an assumption because you would know otherwise as you recharged the batteries and checked the wiring for any faults.
Thanks for the reply. I did check all wires and nothing was out of wack. the battery was a TP 5000 65C and had 60% still in when the power loss happened. It was the first flght so i wasn't pushing my luck. I agree, when it's hot i don't fly back to back.

What upgrades are you guys doing on this bird that seem to be worth the cost? new ESC's 70 amp, new fan units? how about the Change Sun 10 blade fans, are they worth the change?

I like this plane but my problem now is i dont trust it. the first few flights i thought it was very cool. but that was a close call yesterday and I'm not sure i will fly this untill i figure out what went wrong.
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Old Aug 03, 2012, 03:06 PM
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Flat spins are getting easier now that I am remembering to not use ailerons but just elevator and full rudder once I am at the top of the stall. Did about 3 today. I really like the SU and would be hard pressed to choose between the F-18 and the SU-35 if something happens to this one. The guys at the airfield are always commenting and asking questions about it.
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Old Aug 03, 2012, 03:27 PM
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That's a hard call. I'd run it hard a few times on the ground to see if the even hotter conditions of being static trips anything. If it does either cooler days or up the ESC's.
CS, I think only Pete and Flipflop have officially flow CS in these that have given a limited report. Flipflops video show they are good for speed passes. He said it was getting close to 1:1 but he didn't really post anything after that about it... in fact he posted this plane in the CS thread not here.

Pete crashed so not sure what he observed. He used ExtremeRCs CS/2W30 setup with alloy housing so his set up was heavier than factory. But like my ExtremeRC Wemo midi Wemo/2W25 plastic housing, he burned about 60+ amps for who knows what since when I last read anything he said he was estimating. Wish he would just post some actuals since its on many peoples minds. My particular reason for details is though on the bench both perform the same numbers, the CS delivers a different performance curve in theory since none post specifics... that is CS accelerates a fraction slower and has a reputations of losing more depending on the tubes effect.

Wemo in a plastic housing is lighter along with the motor, during which I burned 60- amps actual, producing 3.6kg thrust actual. After talking with Mark at ExtremeRC, he knew what I was shooting for and said of the two he still would go Wemo because its lighter and usually works well in various ducts. It also has better acceleration since my intent on this is 3D not fast passes; though he still said they are neck and neck in that area too. I think I'm actually getting more to be honest. The reason I know it got 3.6Kg was because I had the watt meter and a larger RX battery in it with the 5800mAh 850g battery creating that AUW. Pointing it down on my scale puts it over the scales limit so pinning it to the ceiling confirmed it at least had 1:1 but may have more. And I was surprised that they aren't that loud. My wife normally comes in and tells me to take it outside when I do runs ups but she didn't for the pair. Mark said they never really were loud especially when balanced properly.

I tested the landing gear on my very bumpy dry mixed with crab grass of a lawn and it had no issue getting up to speed with even that poor surface. And I love the steering... can turn around in under a 3' circle but the steering isn't sensitive at center without the need for extra expo.
Gonna go practise some flying ... don't want to dumb thumb this one on her maiden cause of my flying
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Old Aug 04, 2012, 03:22 AM
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I took out the Su-35 with its new HET2W30's today.... and promptly 'broke it' again. SIGH. LOL

It is FAST !!! Much faster than it was with the L2855-2100kvs!
My Dynam Meteor is 'fast' (near 160kph), and this must have been the same or faster (it is bigger so it probably 'hides' speed more so than the Meteor/Habu).

As is usual I took the GPS Logger, but totally forgot about throwing it into any planes that I wanted to log speeds from today!! sheesh.....

Maybe I was 'deaf', or having too much fun.....
It whizzed around and around - mainly at about 2/3 throttle as even that was fast - and I did some WOT low passes..... oh and the twin CS10's sound really great too! Probably a bit better than the L2855's, seeing the HET's can drive more RPM from them....
And I thought to myself "Wow, this seems to have been a long 3 minutes!...??" (timer setting)

About 15 seconds later, just as I approached mself in a low pass at about 5 metres (into the wind - the landing direction), it went "BRRRRRRRrrrrrrrrrrr"... ESC low power cutout!
Hmmm, not a great moment for that but I was quick to assess and react, and straight way banked around a tight 180deg, with a bit of climb to get some height whilst it still had a high airspeed, to come back around......
I dropped it to zero throttle, to 'reset' the ESC but I wasn't going to use power until I needed some, as the battery was probably not impressed already - I don't know (yet) why no timer alarms went off. The air speed was dropping fast and the next 180deg really taxed its remaining airspeed. I am probably lucky it didn't fall out of th air on that turn really!! Notable AoA - too much really.
"Oh oh"... it was floundering as it straightened up, still about 5 metres in the air and maybe 20 metres out from the start of the usable 'runway'/road.

It was my fault..... as in reality I probably had enough height to cover the true needed distance to touch down fine, but I had believed I needed something like 20m more first, to get to the road.... and it wasn't going to be able to do that!!
I gunned the throttle, and it tried to help me.... a bit of a weak whimper of what sounded like 30% throttle sort of thing.
Too much AoA.... too slow... the thrust helped a little bit, as it peeled off to the right and once again headed into the "rough ground/grass lumpy weedy crap" for somewhat of a pancake that I got close to level for impact.

Hmmm, a double snapped off nose.... triple really I guess.
The nose cone.... a jagged section of maybe 40mm approx.... then another similar length section right to the front of the battery....
Boy is it weak up front there!! HEHE
The rest of the plane was totally fine, so that is a nice thing.

The jigsaw puzzle nose area will need splints etc once again - it didn't break at the same joins as last time! They were too strong this time....

Aircrash Investigations are going to want to speak to the "Timer Engineeer" and work out what went amiss there!! (Or order me to have a hearing check!!)

But it was FAST whilst it lasted......
It will fly again.... next weekend.

Under higher airspeed I think the CS10's/inlets gave it better flow and proibably higher thrust than static tests. But I also think the exhaust is a bit restrictive for the CS10's too.
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Old Aug 04, 2012, 10:19 AM
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LMAO sorry for your crash, but i loved the story. Keep up the good work. What are the HET?? I couldn't find them. can someone post a link.
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Last edited by JTAnimal; Aug 04, 2012 at 10:43 AM.
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