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ASP 61FS Just Stopped !!

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Stuphedd11/01/2019 17:16:57
616 forum posts
320 photos

dscf6694.jpgdscf6693.jpgMy pals ASP 61FS in his Magnatilla just stopped in the air on Sunday but the prop still turned .

I took it to bits and found that the crank pin had sheared off ?? Looks like a classic fatigue failure , Is this common ?? and are Just engines the only source of spares ??dscf6692.jpg

cymaz11/01/2019 18:07:16
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8267 forum posts
1144 photos

Yep, that would stop. I had the same a few years back surprise

Jon - Laser Engines11/01/2019 18:13:52
4411 forum posts
162 photos

Not unheard of. In future make sure the engine is not knocking at all as this can be contributory. I have no idea what fuel or prop you were using but dont use too much nitro and dont use a small prop. 12x6 is about the minimum i would use on one of those

Paul C.11/01/2019 18:24:31
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545 forum posts
123 photos

Hi Jon, I have been using 11×7 on my 52 and 61 ASP FS but recently started using 12×6 and found that the slow running has improved and no difference in performance . Not sure if I should go for a larger diameter or not ! Has anyone any experience.

Paul.

GrahamWh11/01/2019 21:32:59
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313 forum posts
35 photos

Paul I have fitted an MA S2 series 14x6 to my ASP FS 61 AR and get 9,000 rpm on the ground with Optifuel 5%. (With an MA K series 14x6 it only gave about 8,500 and the throttle seemed a bit unresponsive above 2/3 in the air so probably a bit too much load). Only just started with this though so I don't know how it will be long term.

My ASP FS 70 AR has been pulling around a puppeteer for 5 years or so with the K series 14x6 and goes very well - overpowered of course in that plane, but that's nice when you want a blast.

Pete - do you know what prop and fuel he was using on the Magnatilla?

 

 

Edited By GrahamWh on 11/01/2019 21:54:32

Paul C.11/01/2019 21:44:49
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545 forum posts
123 photos

I am a weston prosynth 10% user and have been realy happy with the product , over power is never a problem so long as you have a throttle 😉 within reason 👍

Engine Doctor11/01/2019 21:49:49
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2164 forum posts
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I re-built an ASP 61 last year for a club mate. that had sheared the crank pin . You can buy a roller from a bearing supplier and press it in but you will have too cut down the length. I believe its a 1/4 roller. If you know anyone with a old OS 52 Surpass then the crank shaft is direct replacement as ASP copied the OS and bored it out to a 61. I used the OS crank as I had a motor with a broken Cyl Head. A new ASP crank is about £30 . I still have some OS 52 spares and may still have Crankshaft . If interested PM me and I'll check it out .

Paul C.11/01/2019 21:56:33
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545 forum posts
123 photos

Oops pressed post too early, I have ASP 52, 61, 91 and 120 , up to yet have encountered no issues with either. Having said that not having payed OS price/quality I did not expect the same quality from a 'budget priced' engine, so up to yet I am happy with my purchases , time will tell I guess.

Paul.

Paul C.11/01/2019 22:01:57
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545 forum posts
123 photos

Hi engine doctor, do you have any info on the reported ASP engine factory move that has been rumoured, been looking for reliable info but not found a thing ?

Paul.

Martin Harris11/01/2019 23:53:19
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8219 forum posts
206 photos

Crankpin failure is relatively common - and not confined to budget engines. I have a suspicion that rust can start a crack at the sharp edge between the web and the pin - I've seen early failures after extended storage - which is subject to a rocking couple due to the unsupported end.

John Stainforth12/01/2019 00:09:13
282 forum posts
38 photos

Is it possible that the engine has been forcibly turned over when it has been hydraulically locked? That might lead to such fatigue.

Jon, could a high nitromethane content really lead to that kind of fatigue?

Jon - Laser Engines12/01/2019 01:01:30
4411 forum posts
162 photos
Posted by John Stainforth on 12/01/2019 00:09:13:

Jon, could a high nitromethane content really lead to that kind of fatigue?

Anything that contributes to the engine knocking can cause this and some engines like less compression with higher nitro. I think Enya used to supply a shim for this exact reason.

If you think of a knock as a hard crack on the crank pin 300 times a second it wont take much to expose any flaw in the material. In extreme cases a knock will throw the prop off so you can imagine the forces are pretty high.

A chap killed one of our 180's once by using a very large prop and running the engine hot on high nitro with a hot plug. The 180 is a long stroke/high compression engine and it did not take kindly to this. Eventually the gudgeon pin broke and then the piston cracked...which was fortunate as the engine kept going for quite some time with the gudgeon pin broken and it was only when the piston cracked and compression reduced that the chap noticed the problem!

Anyway, if you look for info on knocking/detonation on car/aircraft engines there is loads of info on it.

Martin your rust theory is exactly what wipes out valve springs. A small dot of rust focuses the energy in the spring and thats all she wrote.

John Stainforth12/01/2019 11:22:20
282 forum posts
38 photos

Jon,

Thanks for info.

Cuban812/01/2019 12:01:10
2342 forum posts
8 photos

Same thing on an ASP 120FS. Cost me my lovely YT Spitfire some time ago. Rebuilt the engine and its been faultless in my H9 P47. Probably 'monkey metal' in the first one. Only ASP to ever fail on me and cost me dearly. Character forming.

Edited By Cuban8 on 12/01/2019 12:04:21

Martin Harris12/01/2019 12:12:14
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8219 forum posts
206 photos
Posted by Engine Doctor on 11/01/2019 21:49:49:

I re-built an ASP 61 last year for a club mate. that had sheared the crank pin . You can buy a roller from a bearing supplier and press it in but you will have too cut down the length. I believe its a 1/4 roller. If you know anyone with a old OS 52 Surpass then the crank shaft is direct replacement as ASP copied the OS and bored it out to a 61. I used the OS crank as I had a motor with a broken Cyl Head. A new ASP crank is about £30 . I still have some OS 52 spares and may still have Crankshaft . If interested PM me and I'll check it out .

Interesting - I had an SC61 fail recently and inspired by your post, I've pressed out the broken crankpin - but it's an odd size - possibly 5.8mm although my metric micrometer shows it fractionally over this and it's a tighter fit through the mic than when measuring a 5.8mm drill shank. It's 0.2275" which isn't 7/32" but all I can say with certainty is that it isn't an easily obtainable 1/4" roller. Was yours definitely that size, ED?

Engine Doctor12/01/2019 13:44:52
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2164 forum posts
20 photos

From memory yes. The rollers are easily available but as the ASP crankshaft was such a badly machined thing I replaced it with the OS crank ,straight swap.

Re the snapping . It can be caused by pre ignition. Even ana incorrect glow plug ( to hot ) can cause the problem by advancing the ignition point. If your engine knocks then try adding a second washer under the plug this effectively regards the ignition a little.

Engine Doctor12/01/2019 15:07:36
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2164 forum posts
20 photos
Posted by Paul C. on 11/01/2019 22:01:57:

Hi engine doctor, do you have any info on the reported ASP engine factory move that has been rumoured, been looking for reliable info but not found a thing ?

Paul.

Haven't heard anything as yet .

Martin Re the roller bearing . have a look here . I have thrown the old crank away now so cant confirm size .

Martin Harris12/01/2019 19:32:16
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8219 forum posts
206 photos

Thanks ED - I'd already checked them as they are my first call for bearings (they've already supplied the bearings for this engine!) but they don't list anything in 5.8mm diameter. I have found one place but the postage charges are a bit unreasonable so, with the slight doubt over the measurement, I'm wondering whether to bother at the moment (engine saved from the club bonfire and no home waiting with an empty engine bay). It was a useful exercise pressing out the pin which will definitely be borne in mind if I have a similar problem with one of my "working" engines...or find a need for a 61.

Edited By Martin Harris on 12/01/2019 19:44:04

Steve Hargreaves - Moderator12/01/2019 21:34:10
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Moderator
6689 forum posts
185 photos

My ASP91 did the same last Autumn.....destroyed the conrod & the backplate & rear bearing....sad

wp_20180609_15_46_04_pro.jpg

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Edited By Steve Hargreaves - Moderator on 12/01/2019 21:35:07

Stuphedd13/01/2019 19:58:56
616 forum posts
320 photos

Found out what the "specs " were on the 61 failure .

fuel was Prosynth 2000 10%

and Prop 12x6

Cheers

Pete W

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