A light weight 250 build.

[HeliLust]

Almost 3 years later I'm back at it with the 250 again. It still suffers most of the same old issues its had. Tail problems, yo-yo in the collective and the pinion will slip after a good beating. I've flown it little and wrenched on it a lot over the past few years.

I was going to replace it with an O2 but heli funds this year are few and far between and the cash I get is going into the 700 and possibly a 550. The only thing going for the 250 is now it's fairly indestructible and the past 4 time it's taken the dirt nap has suffered no dammage and I have lots of parts to keep it going for a while.

First things first though I need to get the tail sorted for good hopefully. It has been working for the most part but is sloppy as ever and needs work yet again. After scoping the lynx 180 tail that has recently popped up I thought that would be a good way to go but the cost and availability put it out of the question for me. I think I may have come up with a fix for it now by building a new custom pitch slider and lever. The good news is all the slop is gone from the mess that was. I still need to fab up new pitch links for it to correct some geometry problems it has and think I may have it close to in the bag.

While it's down I have to replace some bearings in the head and sort out the main gear and OWB. For some strange reason it eats OWB's for breakfast and spits out pinions in defiance. Its probably mostly because I beat on it and over speed it in the hope that one day it will explode and nothing will be left of it. Long ago I discovered that I can hamfist the OWB locked solid and this fixes the yo-yo problems but would like to find a better fix for it if I can. Lastly I'm going to swap out the pinion for the bigger on 16t I think it is as the time is right now being that it spit one out last time I flew it.

It's been so long since I've updated my 250 thread and its changed so much I'll give a quick run down of it as it sits today.

300g AUW ready to fly
3050's cyclic
3060 on the tail
250 mx motor
Talon 15 ESC
3s 850 battery
Belt tail
Raked skid mod to keep the tail out of the dirt
Deceased, modded kbar with integrated sat
Plastic mains
DFC head

If I can manage to get it sorted out and reliable I may consider doing a few other things to update it a bit more. For now I have a whole lot of fab work, balancing and maintaining going on in the hope I can sort it out for a while.

[Tech 4 9]

Welcome back.
Do your servo ball studs rub the tops of the h3050s?

[HeliLust]

Originally Posted by Tech 4 9

Welcome back.
Do your servo ball studs rub the tops of the h3050s?

There is plenty of room for them but I probably changed the balls as I have many different ones in my hardware assortment. Even still the geometry isn't perfect but works well enough.

Heres a pic of the new tail parts I made up. The slider is a stock unit with the plastic and bearings removed. The new bearings came off OWB hubs as they are a bit thinner that the originals. In between is a ball link end that has been thinned down a bit and I also left a bit of the end on it to keep it from rotating.

The pitch lever was made from a random piece of plastic and is the 3rd one I made. The first wasn't quite good enough for my liking. The second was painstakingly made from aluminum and tapping the holes I broke my cheesium tap on the last one. It was a huge disappointment for me. For the 3rd one I decided to go back to plastic fantastic because they are easy enough to make fairly quickly and lighter overall.

The only slop left is from the pitch links which I'm going to fab up new ones that are a little longer to fix some of the geometry that's still lacking. Possibly the pro versions maybe a bit longer as well. If they are I will probably go that route.

The grips have the double bearing mod to them and that tightens up well enough. I still have to back cut them in the weight area so they dont get hung up on the pitch slider, a problem I was having previously that was causing tail kick on punch outs.

There is still lots of work left to do and I'm keeping my fingers crossed it will all be worth it in the end but I'm not holding my breath.






Edit, sadly I cant post pics for some reason the forum wont allow me into the attachments section. I probably will have to use the pos enhanced view to get it done.

[Tech 4 9]

Sounds interesting. To bad about the pics.

I'm trying to get my head around this owb thing causing the yo-yo.
If main gear was slipping on main shaft, wouldn't it be more obvious than 'mystery ballooning'?
If one was using the 0 to 100 linear throttle curve, I can see how main gear and shaft would always be changing relationship but if one was running a flat, governed 80% throttle curve there would be a more constant tension on the gear/shaft. Owb/main shaft slippage would seem way more obvious than 'mystery ballooning'. Heck, I would think it would even be audible and would definitely cause yaw twitches along with it..grabbing and letting go like it would.

Maybe I have a different issue.
I need to strap it down and watch head/swash under load.

From memory, it feels like when main shaft is loose vertically..or when blades are outta track and it fights pitch changes until it 'pops' from neg to pos and then visa versa. But theres not much vertical play in mine.

[HeliLust]

Hold the main gear firmly and twist the head toward lock up and notice it's not a solid lock up and has a bit of spring to it. It's usually prominent after a crash that locks the OWB up tight. A new one will fix it for me, but I like to over speed lots and can eat one in less than a flight and get the yo-yo after 2 or 3 over speeds. OWB is pointless to me on a heli this small.

[HeliLust]

I made some new pitch links for the tail today. I ended up with the ball link arrangement sort of by chance as there is barely enough room to get the job done and making ball links is a difficult process. Also posted is my failed bits I made that were not good enough to use.

I still need to get it all nice and smooth and do a bit of fitting and sizing on the links but its shaping up nice now and there is very little slop in the mechanics left and what is there is in the grips now. Even with the double bearing mod to the grips it's still going to have a little that I can't get out.

[Tech 4 9]

Nice enginuity on the tail parts.

There's a uBrian2 on its way for mine. Lookin at the savox sh-0255MG digital servos for it soon. Talon 25 with hw rpm sensor.

(shrug)
-All in