Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines
The Regular Stuff: Chat, Buy, Sell, Off Topic, etc. => General Discussion - Scale Model Gas Engines - Hit & Miss - Throttle Governed - Non-Compression – etc => Topic started by: eec1910 on February 06, 2020, 09:08:58 am
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Thanks for the advice Tom but for the time being i'll leave things as they are and see how they go.
Cheers Trevor.
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Hi Trevor, you might continue to experience occasional flywheel loosening even with well to9oòrqued typical hardened set screws as the flywheel-crankshaft interface receives hard impulse hits. Hardened, serrated tipped self-locking type set screws grip the shaft better. Unless you drill & tap a new set screw hole about 90° to 100° separation, you're stuck with the Worst case, inferrior, 180° set screw locations. You might consider using Loctite Red on the set screws & glueing the flywheels to crank shaft with "on demand" debondable adhesive since after sorting out the crankshaft bearing issues flywheels seldom need removal. Have fun improving the beast, ...tom.
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Glad you got her running Trevor ;D
Kind regards
Ade
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The engine is now running again with a new piston and ring , two new main bearings thanks to Ade(Yozhek) , and new hardened grub screws on the flywheels . New governor springs have been ordered as well , as the original ones had stretched to far , my fault . It's running on temporary springs
which will do for now.
Thanks for everyone's help in getting my engine running again .
Regards Trevor.
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Hi Trevor,
I have sent you an email
Kind regards
Ade
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Hello Ade,
Here's some photos of the crank and bearings,the drive side appears to have flattened out when I reassembled everything and the other one now has a score going round as well as across itself.
Looks like new bearings may be needed, if you can email me on trram@tiscali.co.uk i'll send you my address,and take up your offer for some bearings.
It also looks as though the inside edges are wearing down any idea what could be causing this ?.
Regards Trevor
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Hi Trevor,
Can you post a picture of the bearing and the crank?
Kind regards
Ade
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Thanks for the offer Ade but I've already ordered some hardened grub screws will wait and see if that cures the problem.
The score marks on the bearings run across the outside , the drive side is worse than the other and quite deep running the whole depth of the bearing ,
does this suggest any particular problem ?.
Regards Trevor.
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Hi Trevor,
Glad you bit the bullet, hope you find the cause.
The score marks are on the outside of the needle bearing case? are they lines across the bearing or lines around the bearing? I ask because those bearing cases are usually hardened steel so it would take quite a pinch from and aluminium crankcase to mark them, however if the score marks run around the bearing it may indicate they seized and turned in the cranckcase.
Not trying to insult your intellengence here, i'm just really curious and interested to find the issue you have :-)
I probably have a couple of bearings and can send you some hard grub screws if you PM me your address
Kind regards
Aded
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Have stripped the engine to check the needle bearings and apart from two score marks on the outside of each one they seem fine, they look like pinch points when the crankcase is tightened up.Put the engine back together with new flywheel grub screws,the flywheels have a slight wobble after finally pulling them off and first firing there loose again, will have to try some hardened ones as Ade suggested.Still no idea why the engine stops any help would be welcome.Thanks Trevor.
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Hi Paul,
I guess the M91 suffers from its enclosed crankcase design and does not encourage user lubrication like the M90 does? no offence Trevor, i'm not saying you did not lubricate, just a general hypothesis.
Even with poor instruction and the weaknesses i still think they are good for the money.
Kind regards
Ade
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I had the intention of saving money to purchase one of these engines but seeing the problems that people have
had with them has changed my mind. They seem very troublesome. Are they really as unreliable as they have been
described? My M90 is ok, but are these engines ( M91) worth the trouble? Was the development of the M91 rushed to put it
on the market before the design was ready?
Paul .
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Hi Trevor,
If the engine is stopping suddenly enough to work the flywheels loose then i guess something is wrong internally, personally i would strip the engine and have a look. I think the crankcases split horizontally on the M91? If so try to remove the crank, bearings and flywheels as one unit, this may make it easier to remove the flywheels. You could try a hot air paintstripper gun to warm the flywheel centre and try to twist it off, some penetrating oil helps here too, but be careful not to twist or bend the crankshaft.
The main bearings are needle roller type and so have no sideways control, on the M90 the shell of the needle bearing acts against the crankweb to limit endfloat (bearings are positioned in the crankcase to allow clearance but little side to side play on assembly). As there is little sideways thrust this design is sufficiant. To check the health of the bearing, once you have it apart, just look for scores on the crank where the bearing runs and check the needles are running in the shell freely, not twisted and evenly spaced. They are normally a sloppy fit on the crank so some radial movement can be felt, this is by design. Normally needle bearings are very reliable and require minimal lubrication, but if they have run totally dry the cage may break up allowing the needles to twist and pinch the crank which may possibly be the root of your issues though i would not bet a weeks wages on that being the case :-)
If you need and pictures of how the parts 'should' look just give me a shout.
Hope this helps
Ade
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Thanks for that last post Ade,have tried using Loctite on the flywheel grub screws but the force of the engine stopping still loosens the flywheels.I have noticed excessive play in the main bearings sideways could this be the cause of my problems ?.Has anyone changed these bearings yet and what size are they if I need some and whats my best plan for getting the flywheels off with the least damage caused.
Here's hoping,Trevor.
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Hi Trevor,
I have had the issues with the loose flywheel burring the crank so they don't want to come off.
The flywheels distort very easily and the outer rim is just pressed on, to be honest if you can tighten them up without removing you will save yourself a lot of grief, i think a puller would buckle the flywheel before it pulls it over the burr, and the twist and pull method just gouges out the inside bore of the flywheel and it usually does not run true again when refitted... i know from bitter experience.
Hardened grub screws stop the loosening and the hexagon rounding out, i have some from RC helicopters that do the job.
I'm glad nothing is seizing :-)
Kind regards
Ade
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Thanks for that Ade,the engine is not seizing up as I thought as when it stops it will still turn.Have tried to remove both flywheels but they won't budge so
gear pullers have been ordered can only assume the loose flywheels have created a burr on the crank and yes I will be gentle.Also have removed the governor weights and arms and the grub screws holding the flywheels are loose so new ones ordered could be the problem hopefully !!!.
Cheers Trevor.
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Hi Trevor,
That doesn't sound good, the loose flywheels will make the engine stop abruptly but it should not sieze. Is it 20 seconds from cold?
If it were mine i would strip it and find the component that is picking up before any more damage occurs.
Kind regards
Ade
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New piston and ring have been fitted thanks Jin,only problem is the engine is seizing up after about 20 seconds.
The new piston has been oiled and turns freely have tried the old one and it does the same,when it stops both flywheels are loose on the crank.
Has anyone any ideas what's causing the engine to seize and how to cure it .
Thanks Trevor.
ps hope everyones bearing up under the present conditions.
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Thanks for that Jin,i've ordered one straight away.
Trevor.
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Thanks for that Jin,could you let me know when you put them on ebay.
Cheers Trevor.
https://www.ebay.co.uk/itm/373003370362
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Thanks for that Jin,could you let me know when you put them on ebay.
Cheers Trevor.
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Last message should have said that I have used the Microcosm contacts page to send a message.
Would it be possible to list the items on Ebay ?.
Thanks
Trevor.
Ok, we will be listing piston accessories at EBAY.Jin
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Last message should have said that I have used the Microcosm contacts page to send a message.
Would it be possible to list the items on Ebay ?.
Thanks
Trevor.
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Jin all other emails are getting through to me so no idea what the problem is.Have sent a message through the Microcosm contacts page to see if that makes any difference. Would it be possible to send a paypal invoice to me ?
Thanks Trevor.
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Jin don't know whats going on with emails as all others are getting through.
Can you try this one instead shirleywhirley62@icloud.com.
Thanks Trevor
We still can't send mail to your mailbox! Are you restricted?Jin
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Nick you may be right I didn't realise I put the fullstop after the email address.
So the correct email should be trram@tiscali.co.uk
or shirleywhirley62@icloud .com
Could you try these Jin
Thanks Trevor.
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Jin don't know whats going on with emails as all others are getting through.
Can you try this one instead shirleywhirley62@icloud.com.
Thanks Trevor
Maybe Jin is copying the period at the end?? (after: .com)
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Jin don't know whats going on with emails as all others are getting through.
Can you try this one instead shirleywhirley62@icloud.com.
Thanks Trevor
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A message to Jin,have sent two emails to the address you gave but no reply.
Can you email me with a price inc. any postage to trram@tiscali.co.uk .
Thanks Trevor
Hi, I replied to my email twice and it was returned by your mailbox. What's going on?
Jin
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Hi Trevor, Please try to keep in mind that Jin is extremely busy right now trying to get caught up after a forced 6 week shut down.
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A message to Jin,have sent two emails to the address you gave but no reply.
Can you email me with a price inc. any postage to trram@tiscali.co.uk .
Thanks Trevor
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Thanks for the email address Jin,i sent you a reply at midday UK time yesterday have you received it yet.
Cheers Trevor
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This is a message for Jin,glad to see your back in business .I sent another message beginning of last week to your microcosm site for the price of a new piston and ring for my M91 engine but have had no reply,so i'm hoping this will get through to you.
Thanks Trevor.
Hi,
This is my email address: 163413fc@163.com
You can reach me the fastest through it.
Jin
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This is a message for Jin,glad to see your back in business .I sent another message beginning of last week to your microcosm site for the price of a new piston and ring for my M91 engine but have had no reply,so i'm hoping this will get through to you.
Thanks Trevor.
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Thanks for the info Gil ,I am using Marvil Mystery Oil but at a lot less than 15:1 so it will be increased for the future.I've actually turned the piston 180 degrees and the engine now works and runs the dynamo which it powers.Will still need a new piston and ring though.
thanks Trevor.
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Jin's holiday is extended not by choice but by the effort to contain the spread of the coronavirus. His work place will remain closed for a couple more weeks.
As for the piston, sorry to hear you are having problems.
This will not happen if you set up your engine properly and use a lot of marvel mystery oil in your fuel. 15 to 1 is a good mix.
The fuel should be Coleman fuel (white gas) or ethanol free fuel such as 100 LL aircraft fuel or another pure fuel.
Also retard the timing to top dead center and reduce the spring tension on the governor. This will get it slowed down.
You can run with just one slightly stretched spring or put two fresh but much softer springs on your governor weights.
You must also remove the crank case vent plug to run it. This way it will freewheel longer between hits and run much cooler.
I also like to shave 100/1000 off the piston top to reduce the compression and put a small chamfer on the top edge and the skirt.
I run mine alot and there are virtually no visible signs of wear.
Gil
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Thanks for the quick replies and enjoy your holiday JIN.
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Hello to everyone,this is my first posting and a shout out to Jin.The piston on my M91 engine has become badly scored and needs replacing along with a new piston ring as it's blowing fuel out of the crankcase vent.I have emailed Jin through his contact page on the Microcosm web site but have had no reply.
So i'm hoping Jin sees this and can tell me what it would cost for these parts to be sent to the UK.Many thanks Trevor(eec1910}
Hi, I'm sorry because there are still vacations. At least until the end of this month to work properly. Jin
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I believe Gil mentioned that Jin is on vacation right now? This post will alert him @JinMachine
By the way, Welcome to the forum from Minnesota, USA
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Hello to everyone,this is my first posting and a shout out to Jin.The piston on my M91 engine has become badly scored and needs replacing along with a new piston ring as it's blowing fuel out of the crankcase vent.I have emailed Jin through his contact page on the Microcosm web site but have had no reply.
So i'm hoping Jin sees this and can tell me what it would cost for these parts to be sent to the UK.Many thanks Trevor(eec1910}