ebay accident- Mini Protos lightweight project

[dr dremel]

Hi fellas,

I have been contemplating a lightweight unstretched build for a while, but did not have the nerve to rip apart my perfectly flying stretched Mini. On the other hand I was not sure if I wanted to have another heli in the stable as I´m already cluttering the home office with various heli related stuff.

So I´ve been following an auction for a Mini Protos last week and in the last seconds I put in a bid so low I´d never expected to win this, but I did win indeed. So here I am with a 2nd Mini Protos

It supposedly only had 30 flights and from the first look it really is brand new. It´s stretched but with 325mm SABs, low FBL head, alu pulleys, stock motor and esc. It seems to be carefully built, although it will be stripped down just for peace of mind.

I don´t know how long it will take me to build this up as I´m swamped with work right now and I rather fly the other birds in my spare time than wrench, but I´ll follow spoofman with his build of his 2nd Mini and update this thread as I move along.

Cheers
Dr

[Epoweredrc]

Nice! I am a Ebay Addict LOL

[dr dremel]

Small update: Spooled it up without blades to check if motor/esc are ok, they apparently are. I´m currently waiting for the unstretched tail/belt and will start the strip down when they arrive.

Can someone please measure the unstretched boom supports for me? Don´t know how long the carbon rod should be.

I noticed some transport damage to one of the blades. I filled the cracked tip with epoxy (used a needle to reach down into the crack) and clamped it slightly down overnight. Anti- sticky paper was used to prevent epoxy from glueing to the clamping surfaces. After a bit of sanding tip is straight and smoooth again

[Aryemis]

Originally Posted by dr dremel

Small update: Spooled it up without blades to check if motor/esc are ok, they apparently are. I´m currently waiting for the unstretched tail/belt and will start the strip down when they arrive.

Can someone please measure the unstretched boom supports for me? Don´t know how long the carbon rod should be.

I noticed some transport damage to one of the blades. I filled the cracked tip with epoxy (used a needle to reach down into the crack) and clamped it slightly down overnight. Anti- sticky paper was used to prevent epoxy from glueing to the clamping surfaces. After a bit of sanding tip is straight and smoooth again

The boom supports are the same for stretched and stock, the difference is on the tail control rod only, though you can use the stock one on both stretched and stock length boom (I use stock length on stretch boom to put the CG further backwards).

[dr dremel]

Ah, thanks for clarifying, thought they were different. I will see what length for the control rod I´ll need as I´m still undecided what servo to use.

[dr dremel]

Strip down now nearly finished as parts finally arrived from Fast Lad. Disassembled everything but the head. I only found 2 problems so far:

1st was a mismatched bearing in one of the frame´s belt pulleys, obviously it´s a bearing from the tail pulley.

2nd issue were gritty main shaft bearings. So maybe the heli only had 30 flights, but also at least one crash. Kind of expected this and got me some EZO bearings beforehand. Compared to new MSH bearings they definitely feel smoother, but I don´t know if it will make a difference. They´re normally 5 bucks/piece, but my car mechanic buddy managed to get them for free, so I won´t complain I also got some for the Scorpion motor, but as the motor bearings checked out ok on this bird, they went into my 1st MiniP, which had shot bearings.

[rdlohr]

Excellent. Looking forward to watching your build. Mine is so smooth and quiet I'm really liking it.

Rick

[dr dremel]

I hope this one will be as smooth.

As I hinted in the 1st post this will be my lightweight project, so here are some weights (apologies for my scales, only accurate to 1g).

Biggest saving on the airframe so far is achieved by going with the hollow main shaft.

Surprisingly the stretched airframe is only 3g heavier (not including blades) than non-stretched. Belt is nearly the same, boom 2g heavier, the rest will be the tail control rod I suppose. But weight savings is not the main goal for me to go unstretched, I´m mainly just curious as my 1st Mini was always stretched.

Aluminum belt pulleys may be a hair heavier, but do not register on my scales, so they stay on the bird. The CNC 3rd bearing support is a bit more, so it is already "upgraded" to the plastic part. I know, only 4 g, but it will add up!

[dr dremel]

Bad weather the last days, so I had a little time to do the first "lightweight mods".

First was just to remove the IMO needless (except for looks) horizontal fin.

Also had a crash with my 1st MiniP and cracked a boom support. I stole the supports from the 2nd Mini and salvaged the ends from the cracked one by heating up the epoxy on the ends and thus being able to remove the remnants of the 3mm carbon tubes. As Aryemis pointed out before, the supports are the same length for stretch and unstretch, so I figured it could do no harm to shorten the supports for the now unstretched Mini a bit.

Lastly I could not stand to look at the empty holes on the boom support clamp after removing the horizontal fin. I fabbed up a blocking plate from 0.5mm CF scrap I had lying around and glued it in place. Much easier on my eyes now!

All in all 5g less to fly around, not too bad.

[dr dremel]

Got distracted by my Gaui "X1" project, but I´m back at it.

As there really is no lightweight servo for the tail and I had a TGY 306 lying around I decided to use this. Also to help it a bit with speed I did this mod:

https://www.helifreak.com/showthread.php?t=616095

The gears did fit no problem. Moving the servo horn by hand feels a little tight, but no different than with the "original" gears. I could not note a difference regarding speed on the bench, curious how it will work in flight.

[jmtyndall]

I had a 306 on my tail before. It was great until I started learning backwards flight. It never locked in. Always felt loose, even with a good amount of gain

[dr dremel]

Yes, I´ve also read that this servo doesn´t work for some, that´s why I´ll try it with this mod.

If this does not work out, has someone a suggestion for a light micro tail servo? Or is the DS95i still the best bet? I´ve done a bit of research, but most of the micro tails seem a bit dated (Futaba 3154 for example)?


Going on with the build, the heli came with a pristine 16T pinion. But as I know from my other MiniP I prefer the 15T. I had a spare almost new 15T, which had a defective OWB right out of the package (got a replacement from my dealer, but they let me keep the defective one). The pinion/aluminum part was perfectly fine though. The OWB in the 16T was ok, so I decided to change them.

I removed the bearings from the pinions and tapped the OWBs out with the aid of a wrench and a plastic ring, which fit the outer diameter of the pinion. Gently tapping on them was enough to get them out. To get the good OWB into the right position I inserted one bearing into the pinion and then pressed/tapped the OWB all the way until the bearing sat flush.

I tested it on the bench and it engages/releases smoothly, although it remains to be seen if it´s ok during flight/normal use. If not I´m going to try the new ones MSH is releasing.

[dr dremel]

Next round of weight savings by direct soldering the motor/esc connection. It gives the added benefit of a little bit more room under the battery tray.

I briefly considered Eflite DS76 servos for cyclic, but came to my senses and found a good deal on Hitec 5065s. Still pretty light @11g in comparison to the 21g of the now popular metal cased micro servos.

[MiataJohn]

The 5065 should work well as opposed to the very weak 76's. A lot of complaints about them.

[corrosionate]

It's amazing what some weight savings can do on this little heli. I switched from mks servos to some plastic case Futabas and was able to ditch the external BEC that the MKS's needed and lost 4 ounces off my mini p stretch. It made a huge difference in the feel of the heli it feels more like a 500-550 now than a 450. The only thing I haven't done is switch to a micro tail servo. I'm still using a mini, but it works awesome so I don't want to change it.

It's crazy how light this thing flies, and I couldn't tell the difference in servos at all. The futabas are crazy fast and powerful. Precise and crisp. Those other servos were awesome, but were just added weight for nothing. They'd be better suited to another heli maybe.


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[flyingw]

Corrosionate,

To which Futaba servos did you switch for cyclic?

Thanks,

Paul

[dr dremel]

Corrosionate, this is what I figured also. 1 ounce saved in servos alone in comparison to the Turnigy metal case servos. I have those on my stretched Mini and before them Savöx. TBH I couldn´t tell any difference in flight except that the new servos were not sloppy.

The Hitecs arrived and I did some testing. They do indeed require much less force to stall than the Turnigy, but I guess they will be sufficient. Heck, DoubleCH is flying the Turnigys on his 500, so I guess they are a bit overkill on a 450.

Re micro tail: In comparison to the Savöx mini tail servo I have on my 1st Mini the metal case micro servo saves 5g. Would like to try something even lighter though.

I also got some time on the weekend to decase the FBL unit and put together a nice combo with the Lemon satellite. Weight before was 16g with cases and the stock sat cable, so 7g were saved.

[corrosionate]

Originally Posted by flyingw

Corrosionate,

To which Futaba servos did you switch for cyclic?

Thanks,

Paul

S3156 is what I'm using now. They're smaller and lighter than the MKS ds92a+. Not sure how the other specs compare, but I don't care. These are way quicker than my thumbs are, and plenty powerful for my 6s stretch mini P. And they're running off my YGE60 BEC. MKS recommends a 10A+ continuous BEC for those which added about an ounce alone for me.

This was one of the smartest moves I ever made in this hobby. The MKS's were stripped off me Warp360 when I realized I don't like heavy helis. It could maybe benefit from the extra power in the servos because it's so much bigger and heavier, but the mini P is little and light. None of that big monster stuff required.


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[flyingw]

Corrosionate,

Those S-3156MGs are very intriguing little machines. They're about half the weight of the popular MKS DS-92/93/95 servos and have about 3/4 of the torque. They are a little slower in transit speed, but I'm not sure how that would affect the flying. They are less expensive too.

I applaud your bold choice; thanks for sharing the idea.

Paul

[corrosionate]

Well thanx. And I'm glad to share, though the idea came from a flying buddy at my field. He suggested them and I said what the heck, I'll give em a shot. As soon as I flew it, my MKS's were on the for sale forum. I don't know who has the skills to require faster servos, but I certainly don't. And my flying buddy who recommended them was happy with them too on his 3s mini p. He's quite the 3d pilot


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