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Author Topic: Any way to adjust startup speed  (Read 4908 times)

justinhow

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Any way to adjust startup speed
« on: October 12, 2016, 01:00:33 PM »

In about 2002/3 I built the Model Slipway Yorkshireman tug which is still going strong. Built with Decaperms etc
I have now decided the time is right to do another and I am getting the Model Slipway Tamar RNLI boat (2 x 40mm prop), so I am on the lookout for build photos on these forums and elsewhere - I have some already but pointers to more would be appreciated.
I have also decided to go brushless and my initial shopping list looks like:
  • 2 x Turnigy D3536/8 1000KV Brushless Outrunner Motor, 430watts, OR Turnigy D3542/6 1000KV Brushless Outrunner Motor 665watts
  • 2 x Hobby King brushless car ESC 2S-4S 60A w/Reverse (7.4v-14.8V)
  • Action Electronics P40E Marine Motor Mixer
  • 2 x Turnigy Heavy Duty 5000mAh 3S 60C Lipo Pack
  • Bow thruster?
Does this seem reasonable?
Which motor of the two above (assuming either is appropriate)?

It will be controlled through a Frsky Taranis X9D RC system so I have great flexibility on setting max power, power curves etc.
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Ron Rees

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Re: After a long long break - its time for another model
« Reply #1 on: October 13, 2016, 01:32:16 PM »

The best guy I know for Lifeboat photos is Canterbury Coxswain, you could probably link up with him on his Shannon build, on this Forum. Proceeds from his photos go to the RNLI. Quality and detail is superb.


At 40mm diameter props I assume you mean the 1/12th Tamar kit? Both of the motors you mention would be OK but brushless motors like to run at nearly the speeds they are designed for, in this case 3S, 5000 li-Po x 1000kv equals 11,000 rpm each which is a bit fast for 40mm diameter props and the escs could get hot and reduce your running time. It may (and this only my opinion) be better to slightly reduce them down by running them through belt drives ie. 1 1/2 to one or even 2:1. Which will enable them to handle the bigger props better. I use MXL pulleys and belts from Motionco to do this and it does make a difference. I note the radio you are planning to use and this set gives you the option to reduce the speeds etc down a bit anyway from the TX.


Action mixers work well with brushless motors, I have used them a lot.


From my experience trying out HK car and Buggy Escapes, I have had trouble with them, setting them up and running as a pair. Alex Engel do some very nice brushless Escapes. they are totally waterproof and can be water cooled.(Parts included) They are automatically set up for forward (100%) and reverse (50%) (But can be re-programmed if you wish) Hobbyking do an identical version under its Escapes for boats section. I think they do 60amp ones but those motors, properly set up should only draw 10amps max normal running, so the 30Amp Turnigy 74071 w/c B/L should be OK at 22.00 each or so, worth a look anyway. I've never had a problem with any of them.


Other people will suggest other ways of doing it, so read as much as possible before parting with your cash....sounds good, good luck.


Ron.

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justinhow

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Re: After a long long break - its time for another model
« Reply #2 on: October 14, 2016, 08:47:35 AM »


Thanks for your insight - I will consider it all!
Interestingly I don't think I need a mixer as the FrSky Taranis OpenTX software can do pretty much the same thing on the receiver
I set up the main throttle stick to drive 2 channels and therefore each ESC has a dedicated channel. This can then be programmed (mixed) to reduce/increase the power on each channel (and therefore ESC) depending upon the left and right movement of the steering stick. You can even use "curves" so that there is very little effect when modest left/right movements are made, but gets more aggressive when moving towards the extremes of left/right.

Re controlling too much power (as I may have) - I can use one of the rotary pots on the receiver to set the overall gain on the throttle channels, so if I have too much power (and therefore the stick is only is usable in 50% travel) I can just dial it down.
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justinhow

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Any way to adjust startup speed
« Reply #3 on: October 23, 2016, 11:48:12 PM »

I am new to brushless motors and ESCs and have got the following:
  • Hobby King brushless car ESC 2S-4S 60A w/Reverse (7.4v-14.8V) details here
  • Turnigy D3639-1100 motors details here
  • 11.1v LiPo
All is going pretty well with testing but I have found that the initial startup speed for the motors is quite high (about 3000rpm). Once started I can then reduce the speed quite a bit.
This appears to be a limitation imposed by the ESC as if I use a 6V battery the startup speed is considerably reduced so the motor is capable of slower startup speeds.
Is there any way to reduce this other than just using a lower voltage battery or a gearbox - settings on the ESC etc?
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knoby

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Re: Any way to adjust startup speed
« Reply #4 on: October 24, 2016, 12:25:06 AM »

You can turn down the 'start force' on the esc, see here;


http://www.hobbyking.com/hobbyking/store/uploads/764731122X1256999X25.pdf



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justinhow

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Re: Any way to adjust startup speed
« Reply #5 on: October 24, 2016, 09:00:33 PM »

I have been playing with that - actually my ESP is slightly different and can adjust between 1 and 29% start force. However the actual effect om startup speed apears to be pretty minimal.
It looks like I will have to try a 2S battery rather than the current 3S as the slow speed running will be pretty poor I think currently. Start up revs are 5000rpm or so, and slowest absolute speed is about 3000rpm.
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imsinking

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Re: Any way to adjust startup speed
« Reply #6 on: October 25, 2016, 12:14:55 PM »

You need a program card to set up the ESC easily , if you have one make sure 'Battery low voltage Protection' is set correctly ( I use 3.4v) as sometimes the wrong settings screw up the ESC operation . . .
motor speed is given in Kv . . . in your case 1100 revs per volt  which, at 11.1v (3s) is 12,210 rpm ,  how big is the prop ?
I'm also new to LIPO & Brushless , so shoot me down if i'm talking B****ck's
Bill
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microgyros

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Re: Any way to adjust startup speed
« Reply #7 on: October 25, 2016, 12:46:31 PM »

....
Is there any way to reduce this other than just using a lower voltage battery or a gearbox - settings on the ESC etc?
Yes. With a 555 brushed motor + marine brushed esc capable of 1kHz operation.

How about you try everything that has ever been suggested to you for this model and, one by one, take aim?
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microgyros

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Re: Any way to adjust startup speed
« Reply #8 on: October 25, 2016, 01:27:55 PM »

It reads slightly differently if you begin from Oct 23rd with "Any way to adjetst startup speed"
However 555 motors can take 24 volts or 6s Lipo.
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justinhow

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Re: Any way to adjust startup speed
« Reply #9 on: October 25, 2016, 01:36:38 PM »


You need a program card to set up the ESC easily , if you have one make sure 'Battery low voltage Protection' is set correctly ( I use 3.4v) as sometimes the wrong settings screw up the ESC operation . . .
motor speed is given in Kv . . . in your case 1100 revs per volt  which, at 11.1v (3s) is 12,210 rpm ,  how big is the prop ?
I'm also new to LIPO & Brushless , so shoot me down if i'm talking B****ck's
Bill
Bit confused why this topic has now become a mix of two different threads of mine but anyway...

I have used the ESC card and it works well. Low voltage has been set.
Prop is 30mm.
Start up speed is still rather high with 11.1v - so will try 7.2v LiPo and then wait until I get the hull on the water.
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inertia

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Re: Any way to adjust startup speed
« Reply #10 on: October 25, 2016, 01:45:00 PM »

I'm not an expert in using brushless motors (yet...) but I reckon that 1000kv is way too fast for a scale workboat. You should be looking at nearer 400 kv or even lower unless, as has been suggested, you adopt a reduction drive of some sort. You might be interested to read John Redearth's thread on his recent brushless experiments; it appears elsewhere on this Forum.
Incidentally, the Model Slipway Tamar is 1/16 scale and I've known customers run them with up to 45mm 4-blade props - but not at 11,000RPM!
DM
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microgyros

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Re: Any way to adjust startup speed
« Reply #11 on: October 25, 2016, 02:07:38 PM »

Bit confused why this topic has now become a mix of two different threads of mine but anyway...

I have used the ESC card and it works well. Low voltage has been set.
Prop is 30mm.
Start up speed is still rather high with 11.1v - so will try 7.2v LiPo and then wait until I get the hull on the water.

The term used is" topic merged". You started a new topic on the 23rd of October with relevant information omitted. (the boat)
A 30mm prop, rather than 40mm prop moves the goal posts away from a high torque 555 brushed option to something like a 550.

The brushless esc starts in brute force mode until the motor reaches sufficient rpm to be detected by its esc so you are not going to get a slow start up speed on your present tack. Sensorless brushless powered cars do by virtue of a reduction gearbox. Sensorless brushless motors need a minimum initial rpm in order for the esc to control speed where brushed motors do not.
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justinhow

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Re: Any way to adjust startup speed
« Reply #12 on: October 25, 2016, 03:59:42 PM »

I understand on the thread merge.
A number of other people on this forum do use motors in the 800-1400kv range including for lifeboats, and I do want a reasonably fast lifeboat (I currently have a tug).
I am now aware of the start-up issues with brushless sensor less motors. I did a test with a 6v Lead Acid battery (as I did not have smaller LiPo at the time) and start up speed appeared to be a lot slower - so I think the motor is capable of a slower start-up than it is currently doing (indeed in reverse it is a lot slower [set to 25% power]), but the ESC is not letting it with the 11.1v LiPo.
I went into this knowing that I had a steep learning curve as I have never done brushless before and it has been very interesting.
I will shortly know what it is like with the 7.2v LiPo I have just got hold of and feedback
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microgyros

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Re: Any way to adjust startup speed
« Reply #13 on: October 25, 2016, 04:46:03 PM »

...but the ESC is not letting it with the 11.1v LiPo.
A steep slope, but I think you will get there.
Perhaps ending up with with a reduction gear and scale props but it looks like you have hit the buffers with that esc.
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justinhow

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Re: Any way to adjust startup speed
« Reply #14 on: October 25, 2016, 09:44:31 PM »

OK - so I have replaced the 11.1v LiPos with the 7.4v LiPos and tested again
It has meant that the start up speed has dropped to around 1700rpm (from circa 3200 rpm) and still goes up to over 7000rpm. Minimum speed (once started) can go down to a little under 1000rpm.
I think this will probably be fine although time will tell. As a way of comparison my Yorkshireman tug with 50mm props had props that went up to 3300rpm (Decaparms with 2.6:1 gears) and I would want the lifeboat to go noticeably faster than that.
Now I am awaiting the delivery of the Model Slipway Tamar and the build proper can start.
One of the lessons I have learnt is that with sensor less brushless motors, the speed range (min to max) is not as great (as many multiples) as a brushed motor because they can generally run at lower speeds. However I also realise the ESC can play a large role in the start-up speed, and it is difficult to know before purchase as this info is not really reflected in specifications.
My son who has just got brushed 540 motors which can go from a few hundred rpm to circa 15000 rpm approx (not measured yet though).
All the above rpm figures are in free air running so may well change when in water!
Thanks for all the input on this.
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kinmel

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Re: Any way to adjust startup speed
« Reply #15 on: October 26, 2016, 09:44:29 AM »

Have a read of this thread where people started using brushless motors in the Slipway Tamar....   http://www.modelboatmayhem.co.uk/forum/index.php/topic,36465.msg364162.html#msg364162
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justinhow

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Re: Any way to adjust startup speed
« Reply #16 on: October 26, 2016, 12:13:22 PM »

Have a read of this thread where people started using brushless motors in the Slipway Tamar....   http://www.modelboatmayhem.co.uk/forum/index.php/topic,36465.msg364162.html#msg364162
Yes I remember looking at this thread - it was useful in forming my shopping list. I also noted the person who says he dropped from 3S to 2S but the 3S was rather more fun. At the time I thought why not just adjust it on the RC kit, but now, having played with it myself, it makes more sense.
I also note that someone says they run LiPo's in parallel. I didn't know that was OK and it is an interesting way of getting greater running time.
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inertia

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Re: Any way to adjust startup speed
« Reply #17 on: October 26, 2016, 12:41:35 PM »

I also note that someone says they run LiPo's in parallel. I didn't know that was OK and it is an interesting way of getting greater running time.

Not the best idea I've heard this year. In slightly different states of charge, one pack will try to charge the other up. The current involved would be very high. In an extreme case with NiMH batteries this could be spectacular; with LiPo's it could be fatal - and not just for the pack and the model.
My strong advice is not to do it unless you are 100% certain of what you are doing and the risks involved. If you want longer running time then a) don't hold full-speed for so long; b) take a spare pack with you, or c) fit a larger-capacity pack to start with.

However, as I frequently say, you're blissfully free to follow advice or ignore it - suit yourself.

Dave M
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justinhow

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Re: Any way to adjust startup speed
« Reply #18 on: October 26, 2016, 01:39:24 PM »

Well, as LiPo's somewhat scare the living daylights out of me, I will heed your advice.
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Ron Rees

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Re: Any way to adjust startup speed
« Reply #19 on: October 27, 2016, 07:09:36 PM »

LiPo's are great!!!, I've got loads of them..in Tugs, as well as fast models....And they really are not as dangerous as people keep saying.


That said, if you abuse them they will bite back!!..So, 1. Never charge them in the model....2. Don't go to bed and leave one on charge....3. Don't keep topping them up after every short session at the lake, run them down to near the 3.4 volts per cell mark now and again..4...Fit a cheap audible warning and voltage indicator to the balance lead in your model...5...Trickle charge them if possible and not too many rapid high amperage charges. 6...Overwinter them at a bit over half charge.....7...Don't stick a model knife or screwdriver into the pack and protect them with a bit of foam in the boat.


If the plastic appears to be filling with air, you probably haven't stuck to rules 1 to 7 above, so bin them.   Buy decent quality ones.


These apply to nearly all our batteries though. I've never had one melt or catch fire...ever. and Iain at Component Shop and his team charge and discharge Lipos all the time, they've done thousands of them and never had a blow up or a fire (So he tells me,anyway)


Don't listen to old wives tales...They are lighter, more powerful, much smaller and can be discharged rapidly if needed for speed..the best thing since sliced bread.


(That should get the chins wagging!!!)



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justinhow

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Re: Any way to adjust startup speed
« Reply #20 on: October 27, 2016, 07:47:10 PM »

I am (somewhat) reassured!
The bottom line I guess is treat them with respect and they won't bite you in the a**e.
Reminds me of how I should have treated my wives (yes plural)! However, too late for that me thinks  %)
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inertia

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Re: Any way to adjetst startup speed
« Reply #21 on: October 27, 2016, 10:47:31 PM »

I wouldn't disagree with anything Ron has said, but his 'rules' don't cover using two packs in parallel. I would still advise against it but hey - what do I know?
And will somebody PLEASE correct the spelling of 'adjust' in the title of this thread?   >>:-(
DM


 :-))  Took some time
ken

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JimG

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Re: Any way to adjust startup speed
« Reply #22 on: October 28, 2016, 09:35:24 AM »

I have regularly used 2 Lipo packs in parallel without any problems. Both in a plane and in a fast electric boat. These were 3S 3200mAh packs used with a twin ducted fan giving around 6 minutes flight or 5 minutes running in the boat. The batteries are normally charged the night before use and any minor differences in the cells do not produce any problems when they are connected together. If you were to connect up a fully charged pack to a discharged pack then there may be problems but common sense should stop this from happening. Just keep fully charged packs seperate from used ones and use a battery checker first if you are not sure about the state of charge and you should have no problems.

Jim
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inertia

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Re: Any way to adjust startup speed
« Reply #23 on: October 28, 2016, 11:19:43 AM »

but common sense should stop this from happening.
Jim
A commodity which is evidently in short supply worldwide, Jim. I could tell you some tales...  :o
Dave M
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Ron Rees

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Re: Any way to adjust startup speed
« Reply #24 on: October 28, 2016, 06:40:55 PM »

Thanks for the vote of confidence Inertia, and you are right, I didn't answer the question.


Despite all the horror stories Li-Po's are just batteries, like any other. The source of the power is slightly different, just some strips of polythene bag like stuff and a scraping of Lithium paste etc. You wouldn't think twice about putting two NiMh packs in Series or Parallel and the same goes for Li-Po's. Ideally they should be a matched pair and charged to the same amount.
 
In fact in multiple celled  Li-Po battery packs, each cell is linked to the next in Series inside it anyway, with a common earth to all individual cells and a power lead from each cells' positive, hence the little white balance plug. Say an 11.1 volt Li-Po, then 3 positive wires and one on the end, usually black being the common negative. (The 3 positives can be any colour in fact)


Remember Series wiring, ie. daisy chaining one cells' positive to the next cells negative will increase the overall voltage but capacity (How long it lasts) will remain the same. In this sense you will use the black output wire from one pack and the red output wire from the other to connect to your speed controller. So two 11.1v x 2500 Ah batteries would supply 22.2 volts at 2500 Ah, This certainly wouldn't slow down the startup speed, which was the original question. I would suggest it is safer using a 6 cell battery (22.5v) at 2500 Ah if you want that effect.


Extending the running time without doubling the voltage ie 5000Ah at 11.1v means running them in Parallel, which I do all the time and a made up 'Y' lead which couples both cells to each other black to black and red to red is safe and works well.
 Action do some very nice connection boards with fuses etc if you decide you want to start cutting plugs off, which I don't like the idea of as then there can be charging problems.


Treat them like ordinary batteries, use the proper rated cables and good quality plugs which are soldered, lipos are capable of discharging their whole current in a split second if you short them out, that means Bonfire Night comes early if you cut both plug leads off at the same time!!


Good luck.


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