Mayfly - by Peter Valentine

Here’s one for Pete
Retro helicopters
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PaulJ
Posts: 598
Joined: 16 Feb 2018, 19:01
Location: Ipswich, UK

Re: Mayfly - by Peter Valentine

Post by PaulJ »

Pete, I have a small piece of 2mm Delrin from which you could make a disc..... It is slightly flexible and no tougher plastic exists....? pm'd you.

Paul
Pchristy
Posts: 413
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: Mayfly - by Peter Valentine

Post by Pchristy »

Many thanks for your kind offer, Paul! PM sent!

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Pete
Pchristy
Posts: 413
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: Mayfly - by Peter Valentine

Post by Pchristy »

PaulJ was kind enough to send me some Delrin discs to replace the servo arm acting as a universal joint. They arrived in the lunchtime post today, and drilling them and fitting was much quicker and easier than I expected! (Its always easier, second time around! ;) )

I used the original servo arm as a template for drilling the disk, as the original holes had been perfectly aligned. There was enough residue of the original "stub" that fitted onto the servo output shaft to act as an accurate central locator in the hole in the middle of the Delrin disc, which made accurate drilling a doddle!

Once drilled, at was just a question of cleaning up any flash left behind and re-assembling. The re-assembling is always a bit fiddly because of the tiny size, but again, second time around, I knew what to expect!

ImageCoupling_3 by Peter Christy, on Flickr

ImageCoupling_4 by Peter Christy, on Flickr

The Delrin disc is quite rigid, so once again, I've left the screws a little bit loose to provide some compliance (1/4 turn loose on the 2mm allen caps, and 1/2 turn on the 6BAs).

All I have to do now is wait for the wind and rain to stop! I think it could be a long wait.....!

Many thanks to Paul!

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Pete
Tobe
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Joined: 16 Feb 2018, 06:19
Location: Varberg or Stockholm, Sweden

Re: Mayfly - by Peter Valentine

Post by Tobe »

The weather is season matter...

Allt the best Pete
Cheers,

Tobe
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Shaun
Posts: 1049
Joined: 15 Feb 2018, 21:49
Location: West Yorkshire

Re: Mayfly - by Peter Valentine

Post by Shaun »

Pete,

I may have a small new universal joint from a model boat.

Any use?

Shaun
Pchristy
Posts: 413
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: Mayfly - by Peter Valentine

Post by Pchristy »

Hi Shaun,

Thanks for the offer, but if its the type I think it is, they are not man enough for the job!

The original Lark used a sold aluminium shaft adapter at the tail rotor end. Simple and never failed! For some reason, MicroMold decided to "improve" it by adding a small u/j made by Huco. These failed quite rapidly!

I think it was UV sunlight making the plastic go brittle (boat couplings tend not to be exposed to sunlight!), but they didn't last long on a heli!

When I rebuilt the Lark for electric, I replaced a lot of the "upgrades", including that u/j. It certainly flies better and should be more reliable now its back to the original design!

;)

--
Pete
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Shaun
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Joined: 15 Feb 2018, 21:49
Location: West Yorkshire

Re: Mayfly - by Peter Valentine

Post by Shaun »

I'm away atm Pete but I'll post a pic of it on Monday.. that's assuming I can find it so you can see if it's any use.
Pchristy
Posts: 413
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: Mayfly - by Peter Valentine

Post by Pchristy »

Cheers, Shaun!

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Pete
Pchristy
Posts: 413
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: Mayfly - by Peter Valentine

Post by Pchristy »

Quick update: Managed to finally get hold of a 2500kV outrunner motor to replace the current 3000kV. It is actually slightly smaller and lighter than the 3000kV, but within the power range.

First hops indicate little or no difference in flight performance, but reduced current consumption.

The kV figure can be (sort of!) regarded in much the same way as a gear ratio, and I had felt that the reason for the ESC overheating issue was that the 3000kV was too high geared - a bit like trying to drive around town in 5th gear!

I was unable to change the gear ratio of the heli, but hopefully this reduction in the kV will be a better match. A couple of tentative hops in the fading light look promising - no shortage of power - but it was a bit gusty and the sun was in my eyes, so I couldn't carry out a prolonged hover. I may have a go tomorrow at my local "test site" if the weather is OK.

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Pete
Pchristy
Posts: 413
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: Mayfly - by Peter Valentine

Post by Pchristy »

Further update: As a result of the lockdown and the appalling weather recently, I decided to use the time for some more "fettling".

First up was to improve the mesh between the main gear and the pinion. This had always been very slack, and I suspected it was skipping occasionally. It was easy enough to remove the layshaft bearing block, after which I "Dremeled" out the holes a bit to allow for some adjustment. This has now got the mesh just about perfect, and the transmission now feels much smoother!

A side effect of this was that the belt tension was now too tight, which meant making a new motor mount. Whilst doing this, I took advantage of the opportunity to move the motor more rearwards, so that the pulley now sits better on the shaft.

A test hop on the garage roof this morning saw me achieve the target 4 mins flight time, without the ESC shutting down, and leaving 14% in the (very old!) LiPo. However, the motor and ESC were very hot after landing, which makes me think I can go even lower on the motor kV. I've found a 2200kV motor in the same can as the present one, but it is coming from Hong Kong, so will take a while to get here. Should be a quick swap when it arrives though!

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Pete
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