Tail Exploded!!!

[DaveB]

It always happens to someone else right? Wrong!!  

I just finished fitting an H8 motor to my ECO 8 and thought I'd check for vibration and set the throttle etc. before I put the main blades back on... Well, thank God I did... Had it spun up on the garage floor when bang...





So, I guess I now see the need for thrust bearings on this thing... although soon there won't be much original ECO8 left.

Would someone in the UK please be kind enough to tell me what I need to order for both the tail rotor and main rotor ally head please.

Thanks,

[salk31]

Dave,

Do you run it at higher than normal revs?

Is it just the photo or is the side of the bearing pretty
flimsy?

Sorry, no help just questions.

Cheers

Sam

[Malcolm]

It seems the QC of Ikarus parts these days are getting worse.

I've been running MS carbon tr blades since I got my Eco 8 some 4 years ago, however I did replace all the bearings with ones from Model Fixings which might be worth doing rather  than replace with stock Ikarus parts again

[DaveB]

It is possible the revs were higher than they've ever been as the main blades weren't on and it's an H8 brushless motor. However, they certainly weren't higher than it should be able to cope with. This actually happened at about half throttle. First the bearing gave up, which left the tail blade held on by only the pitch control arm (plastic ball joint). Now I don't know what sequence this happened in, but the result is that the pitch control arm itself is split and the plastic ball joint split the full length of the screw thread. This all happened in less than a second. I am just grateful the blade, screw and/or ball joint didn't hit me in my eye.

On inspecting the bearing in the blade that was still attached in the photo, there is very discernible play between the inner and outer rings and so that is obviously on it's way out too.

I am still very much a learner having only got to the nose in hover stage with my heli's and so this hasn't got many hours on it and it's never been flown agressively. The tail has never hit the ground and so the only thing that can account for this is poor manufacture and/or the bearings simply aren't up to the job. Most of the force must be outward from the center of the bearing and so the only cure I can see is to fit thrust bearings. I've looked at old posts and Rads site etc. but unfortunately all the links for thrust bearings don't seem to exist or are for the head and not the tail.

I've spent an absolute fortune on this thing and now it still it needs more. I don't give up on things easily, but when this happened I did mutter to myself, "what's the point?". While not wishing to stirr up any past bad blood with Ikarus... They sell the ECO8 and they sell the H8 motor for it. Nowhere do they say the ECO8 will self destruct if you fit this motor  

I bought an H8 and Lexors controller from Ikarus because I figured they would be perfectly matched. One of the reasons I was testing this without the main blades is because I couldn't believe the speed the motor starts at. It doesn't start until 1/4 throttle which according to the controller instructions is correct, but when it does, it does it very suddenly and at quite high speed. This is with the thottle curve set back to 25% at 1/4 throttle. I am convinced that when I have it's tail rebuilt and finally put the main blades on to test that I soon as I spool up, the blades will twist in the head and it will self destruct on the ground. I have tried setting the throttle to 10% at 1/4 throttle, but the only result there is that the motor doesn't start. It is obviously capable of running at very slow speed because once it has started I can slow it down to a crawl, so can anyone suggest why it starts so agressively in the first place?

If everything doesn't work properly after I've fixed this and fitted yet more non standard kit (thrust bearings), there will be another ECO8 for sale... I don't have any of these problems with my Raptor.

Sorry for the long post... I'm not happy about this.  

Regards,

[Vince]

Dave,

Did you say you spun it up with out the main blades on? May be without the load of the main blades the head speed was quite high and this caused the tail to explode due to too much force? I always thought it was bad practise to spool up a unloaded head or is it OK with governed brushless motors  

I got a full set of bearings from Modelfixings including the tail & head thrust bearings. The only thing that I could not get was the "T" nuts for the head thrust bearings, these I got from fxaeromodels in the states.

Vince

PS. I hate it when it takes me ages to reply and the thread changes in that time  

[salk31]

Dave,

My skills have been the weakest link so far but it is
not comforting to think the tail could explode because
it is only held on with a thin lip of tin.

A full rebuild/check with model fixings bearings seems like
a good idea.

Im not sure comparison with Raptor is totally fair.  Thunder Tiger has a
bigger end price and end weight budget to play with.

Cheers

Sam

[DaveB]

Yes I spun it without the main blades on and while I agree this would enable it to rev slightly higher than normal, this was no faster than 50% throttle and so I don't believe any faster than it has spun before. I understood it was 'normal' practice to run a heli without it's main blades to track down vibrations, do set up etc.

As for Thunder Tiger costing more, I'm sorry to say my ECO8 is by far my most expensive heli. My Raptor 30 has some of the best kit on it, such as a CSM 560 gyro and Futaba digital servo and it cost me about GBP800 to build. My ECO has cost nearer to GBP1000  so far and it still has the 'standard' GWS radio gear on it. This cost has come from all the upgrades *required* to get it fly acceptably as well as one accident before it had even flown.

Thank you for the info on the bearings, I'll have a good look at their site and see if I can track down what I need.

Regards,

[DaveB]

I cannot find thrust bearings for the tail on the model fixings web site. Could someone confirm the correct size please? I think they are 6mm OD, 2mm ID and 3mm Depth, is that correct? Also, the head bearings are 10mm OD, 4mm ID and 4mm depth, is that also correct?

Many thanks,

[Vince]

Dave,

I would of thought that 50% throttle would give a very high speed. Take you car how much throttle does it take to redline it when it's in neutral? You had no load on the rotor head so 50% of your power turning nothing goes a long way, a lot further than 100% turning the load of the rotor blades. I don't know and am most likely wrong but it would answer why you tail exploded. You can get head loaders for 30 size and above and I see Dream-Models is recommending spooling up an unloaded head so I'm confused on this one. If you need any help don't forget I'm only a few miles away from you.

Vince

[Vince]

DaveB @ Sat Jun 04, 2005 4:02 pm wrote:

I cannot find thrust bearings for the tail on the model fixings web site. Could someone confirm the correct size please? I think they are 6mm OD, 2mm ID and 3mm Depth, is that correct? Also, the head bearings are 10mm OD, 4mm ID and 4mm depth, is that also correct?

Many thanks,

When I rebuilt the dunked ECO I got from HARRomeo I ordered the following from modelfixings:
MF-MFB-006 3x7x3 Flanged Radial Ball Bearing : 4 : 1.75
MF-MTB-007 4x10x4 Thrust Bearing : 2 : 6.00
MF-MB-023 4x11x4 Radial Ball Bearing : 4 : 1.50
MF-MB-003 2x6x3 Radial Ball Bearing : 10 : 1.20
MF-MB-008 3x7x3 Radial Ball Bearing : 6 : 1.20
MF-MB-091 6x12x3 Radial Ball Bearing : 2 : 1.20
MF-CB-01 6x10x12 One Way Clutch Bearing : 1 : 6.82

I also had a new set of tail thrust bearings I used but can't find where I got them from, maybe I got them with all the bits from HARRomeo  

It is posted somewhere the size, I just can't find it yet  

Vince

[DaveB]

Vince, I think you're absolutely right that the head speed was higher than it would have been without the blades. My point though, that I think is being missed (probably I didn't explain it well), is that this was not some super human phenomenal head speed. If I had to guess I would say it was around 1000 to 1200 rpm. In other words, a head speed that the tail rotor blades should be able to stand without any problems. I am utterly convinced that had the tail rotor not 'exploded' on this test, it would have done during my next flight. So, I am actually glad in a warped way that it went when it did. I still do feel however, that the standard bearings are not suitable for the task demanded of them.

I remember you asking me in a previous thread where I am in the world, but I don't remember you replying to say where you are. Please drop me a PM and let me know as I'm sure it would be good to meet up some time.

Regards,

[salk31]

Dave,

Looks like coming from Raptors set your standards higher than
the quality of the base eco 8. For me the standard eco 8 with
only a few upgrades is more than good enough (although
lots of the components do seem very dodgy). My only point
about the thunder tiger costing more was that presumably
the lower kit price gives Ikarus less room to make a profit.
The concensus seems to be that if you have standards the Mikado
helis are better value than upgrading an Eco. Sorry, 50/50 hindsight
isnt much help.

I often test without the main blades. I usually run at higher than
normal revs to check that in normal flight have margin of safety.
The speed controller algorithms are not obvious to me. In governor
mode Im not sure how they establish what 100% revs is. My best guess
is continual approximation.  Im sure you would have been able to hear
if the revs were stupidly high during your test. I was asking about your
normal flying revs. Lot of people seem to favour much higher than
standard revs.

Cheers

Sam

[TMorita]

Based on prior experience, the headspeed is about 10% lower at hovering pitch than at zero pitch.

So, I don't think the tail should have overreved.

Toshi

[Vince]

Dave,

Years ago I had a tail blade let go while I was hover a blinged Shuttle ZXX. I had never whacked the tail but the grass was a bit long in the cow field so I put it down to that. When I turned my stock ECO into the 2 blinged ECO's I now have I made the discission to go thrust bearings in head and tail on both.

IMHO the ECO is crap as stock but once blinged seems to be a great little bird but not for beginners. I'm having fun with my 2 just getting them flying nicely.

I'm also having fun flying my XRB Lama round the house, annoying the kids with it and herding them like sheep  

Vince

[Vince]

TMorita @ Sat Jun 04, 2005 4:45 pm wrote:

Based on prior experience, the headspeed is about 10% lower at hovering pitch than at zero pitch.

So, I don't think the tail should have overreved.

Toshi

By your reasoning the load of 0 pitched blades is a lot greater than the load of no blades. So a possible higher head speed          

Vince

[DaveB]

salk31 @ 4th June 2005 wrote:

Looks like coming from Raptors set your standards higher than the quality of the base eco 8.

Sam,

My ECO 8  is my second heli after a micro Twister FP that I initially taught myself to hover with (tail in). I bought the Raptor after having lessons on one as my third heli. I've a lot of experience now with the ECO and this latest incident is just the latest in a list of things that aren't right with it. The base price of an ECO 8 kit and a Raptor 30 kit aren't actually that different. The difference seems to be that when you've built the Raptor you can just fly it, time and time again. The ECO 8 on the other hand has to have essential upgrades added (Auto hub, tail boom support to name just two). Then you find that while it will fly, you have to spend even more on it to get it to fly with any reliability, predictability and performance. Bottom line, in my opinion of course, they should stop selling the current ECO 8 kit and start selling it with the required upgrades for more money... including thrust bearings!!!  

I agree that hindesight is a wonderful thing and I've given the same advice to other people thinking of buying an ECO. Will it fly out of the box? Yes. Will it fly well? No. How much will one cost? GBP600+

Regards,

[Silvashadow]

Dave,

I got my tail blade thrust bearings from http://www.smbbearings.com/. You are quite right in that they are 2 x 6 x 3mm and SMB's part number is  F2-6 EZO. You will need to use 2 x 12mm cap head bolts to attach the tail blade holders, the thrust bearing will rest on the outside of the existing radial bearing. Make sure you use the black oxide coated hardend type bolts. There will be some slop in the blade holders, but don't worry about it as under load it all goes rigid.

Hope this helps.

Graham S.

[DaveB]

Graham,

Thanks for that. I ordered the bearings for both the tail and head from SMB today... excellent service. I've also already got some suitable bolts (hardened steel) for the tail but I am having the devils own job finding the 'T' nuts for the head. FX say they're out of stock and have no idea when they will get some. A search on T nuts only finds wood working ones with spikey bits... anyone any other suggestions?

Thanks,

[Vince]

You will also need the cups for the bearing. If you can't get any I can always strip the ones from my spare bird so you can get some made locally.

Vince

[DaveB]

That's a very kind offer Vince, and something I hadn't thought of. Do I need them for both the tail and the head or only the head? Hopefully I can find the right thing somewhere.

Thanks,

[scoot]

you dont neccesarily need thrust bearings for the tail, I have been running 2 radial bearings (instead of the stock 1) since I got my Eco8 and have never had any issues with the tail.  You will need longer bolts though.

T nuts can be made from captive nuts no problem, cut the spikes oiff and shape the with a dremmel.  I have some captive nuts at home that would work if you want me to send you a couple.  You could always make a longer feathering shaft, that would work as well but more tricky without the right tools.

The hardest thing to find is the cups for the thrust bearings, still havnt found or made any myslef yet so if you do get some made can you do an extra set for me please.

Scott.

[DaveB]

I am wondering if I need these cups? The bearings I got from SMB appear to me to have the same size hole in the bearing itself, as the washers... that surely would keep them centered on the bolts? I assume that is the purpose of the cups? Otherwise, I'm not sure how the cups would fit? Having said all that, I came across this in another post that I wish I'd found a few days ago...

http://www.cmehobbies.com/catalog/thrust_bearing_kit_4130481.htm

If I do need to get some cups made, once I understand how they fit etc. then I will gladly get more made for other people.

Regards,

[scoot]

the cups go round the outside of the thrust race not through the middle.

it goes radial, thrust race with cup then radial again.  So does the outside radial bearing have a bigger inner diameter to take T nut?

There is a pitcure on here somewhere (this forum) of how it hangs together, I'll see if I can dig it out.

[scoot]

check this thread out for the picture, Q posted it near the bottom of the thread.

http://www.rchelispot.com/viewtopic.php?t=1814

[DaveB]

Perhaps I'm being dense (most likely) or just not seeing something... the bearings I ordered for the head are OD 10mm, ID 4mm. I'm now wondering if I got this wrong? However, in the drawing, that I have seen a number of times, I see no mention of 'cups'. As far as I understand it, the standard bearings are 10mm OD. The hole in the head blade holder is 10mm. Certainly with the bearings I've got, a cup wouldn't fit... but then I still wonder what is the purpose of the cup as the bearing is confined within the hole in the head, or tail, blade holder. Does that make sense? What am I missing? Did I get the wrong size bearings for the head?

Each bearing is a washer, bearing, washer. Certainly for the tail, the inside diameter of the bearing is 2mm, same as the washers, same as the bolt. The bearing therefore will be kept central by both the bolt and the fact the hole in the blade holder is only 6mm. I am aware that I should use a washer with a larger ID for nearest the standard bearing so it only rests on the outside ring.

Thanks.

[scoot]

yep confuses the hell out of me too which is why i probably havnt done the mod.  I want to do it but can never get my head around it.

The picture doesnt even show a cup for the thrust race, it does show that the t nut goes into the centre of the thrust race though so the ID of the thrust bearing and associated washers must be bigger than the normal radial bearings, right?  You can also see a gap between the thrust race and the blade grip, is that ok?

Can someone who has done this mod explain in very very very simple terms how it all hangs together please.  Do you need a cup round the thrust bearing assembly, does the thrust race have a larger ID to take the T nut?  Am i just being thick?

[DaveB]

OK, I spotted at least one deliberate mistake in my post above The standard head bearings and therefor the hole in the blade holder is 11mm and not 10. So I think the 10mm OD bearings I got are OK as they ideally shouldn't touch the sides. However, you've got me wondering on the 4mm ID and the T Nuts. As it is, I've just given up wondering and ordered the full kit from the above URL in the US. It looks to me as though that has everything I need.

I do think it would be really useful if someone who's done the full conversion could post the idiots guide to it, not only for me but for everyone else who will need to do this. If there aren't any volunteers, then once I've got all the bits and completed the job, I'll happily write it all up.

Regards,

[DaveB]

I just got to tell this... 15 minutes ago I ordered the thrust bearing kit from CME in the US... I put a comment on the order that I'd really appreciate them sending them as quick as possible. 2 minutes ago I got an auto notification that the order has shipped and a personal email from Chris telling me he'll send them as quick as possible... TRULY EXCELLENT SERVICE.

Wish I'd found the link at the weekend.

Regards,

[Woogie]

Can you post a link Dave

[DaveB]

Sure, it's in one of the above posts... but to save you looking...  

http://www.cmehobbies.com/catalog/thrust_bearing_kit_4130481.htm