Laser Engines - Technical questions

[Don Fry]

I would reinforce Jon's comments. It needs to be balanced. There is a bloke on the net, American with a Polish name, who describes a very nice method to ensure a centered lathe.

I've not done heavy weights, but I made a 300 gram spinner nut, for a friend, what clamped down on a commercial backplate/prop housing. Prop was a 18/6 APC. It ran nicely. Tickover was very smooth. The engine mounting was rigid.

[Martin McIntosh]

Here is a pic. of my Hurricane spinner. 1.33kg.

[Jon H]

I have been a little conflicted on this for a few days as i see this from two sides and know Martin personally. In this post i have been forced to take off my modelling hat and replace it firmly with my manufacturer hat so the following is not a personal attack against anyone.

As a manufacturer my official position is that we (Laser) do not recommend filling spinners with lead. Certainly your warranty will go out of the window and in the case of a failure of some sort you risk doing serious damage to the engine and model. There is also the issue that a very heavy spinner being thrown off a model could be lethal if it hits someone, be that in the pits or falling from a great height. Given the potential balance and resonance issues the chance of a failure is quite high.

As a result of these issues lead filled spinners are not recommended or supported by us. We also do not recommend anything else (eg crankshaft extension) that adds significant mass to the end of the crankshaft.

This is not a topic i am willing to debate as i have made my position clear above and wont be changing it.

[Paul james 8]

Absolutely agree with your sentiments Jon.

Adding mass to the spinner, given the way it is attached to the crankshaft is very dicey indeed.

[Martin McIntosh]

Don`t blame you for stating as above Jon. I was just saying what worked for me on that motor but cannot recommend it. I did try this briefly on a 180 but it was a lousy pressed spinner and, shall we say, did not like it.

[Frank Skilbeck]

Posted by Frank Skilbeck on 05/11/2019 10:30:01:

Posted by Frank Skilbeck on 25/10/2019 13:40:15:

Last year I acquired a 2nd hand Laser 150, the version with the vertical plug and Irvine carb, it runs great but spews oil out of the front bearing. I remember the seller telling me the bearings had been replaced but I think the front bearing must be faulty. Before I strip the engine down is there anything else that could cause this to happen?

Lastly any recommendations on replacement bearings.

Thanks.

OK, I've removed the back plate and front housing, breather is clear, bore and piston look good (compression is excellent) and all parts were lightly oiled and oil was clean. Going to pull the prop hub off later today and replace the bearings, which is best for the front bearing, metal or rubber seal?

Also going to do an old 62 I acquired up that was all gummed up with notchy bearings, will then bring my Laser collection to 5

OK replaced the front bearing on my 150 and also put on a slightly larger pipe on the breather (previous one had fuel tube connected to a further brass tube), couple of 10 min flights on Saturday, engine ran fine and no oil in the cowl. Hopefully cured it.

Not had a chance to run the 62 yet.

Edited By Frank Skilbeck on 18/11/2019 16:55:33

[Alan Hilton]

I have made several heavy sleeved prop nuts / spinner adapters out of 19 mm hex section and a matching prop washer out of 22 mm bright steel bar,about 10 mm thick .This adds quite a bit of weight ,and have no problems.

Alan

[Paul james 8]

Nice one Frank!! I tend to run 2RS bearings in the front and just take out the inner seal. Can't see any point in just using ZZ for this application.

If you have a real gunky one once you've fully stripped it I can thoroughly recommend cleaning all the parts in hot water with Arial Biological washing powder, couple of before and after photos if you are interested, gets them all clean without the risk of corrosion.

This is my 62....

[wingcoax]

The use of Ariel powder is much better at getting them clean than other powders that tend to give you a matt grey finish.

[Paul james 8]

Posted by wingcoax on 18/11/2019 18:17:29:

The use of Ariel powder is much better at getting them clean than other powders that tend to give you a matt grey finish.

It certainly is, I tried all sorts to get my engines clean and this is my favourite.

I collect and refurbish engines and find that many have quite old castor residue to get rid of, most need new bearings and are then as good as new!

[Jon H]

For all enquires about cam timing ask Paul as he seems to have it right

I might give the washing powder idea a go myself. Many of the engines that come back for service are in a mind blowing condition and it can take half an hour of cleaning just to unearth the blasted thing.

Should your engine become a lawn dart at some point please do me a favour and give it a clean before sending it in. Im not an archaeologist and the next clump of mud i get back is likely to go in the bin even if there is a fossilised engine inside :P

Oh and while we are at it, if you never actually take a peek inside the cowl of your model and never clean your engine dont get all grumpy when i give you a large repair bill due to debris in the cylinder causing all sorts of damage. The two most common faults i see are bearing failure and debris ingestion. Both are caused by simple neglect and lack of maintenance. Its totally preventable and a little pro active maintenance is well worth while. Sending it back after metal flakes start coming from the exhausts is too late, its already broken!

Perhaps i should start a rogues gallery of neglected engines and the horror within?

[bert baker]

Perhaps i should start a rogues gallery of neglected engines and the horror within?

Nooooooooo don’t do that

[Chris Walby]

The rogues gallery should be a list of people who have bought engines and are not using them.

On an annual basis owners should declare the number of hours the engine/s have run and if not sufficient then returned to Jon for resale.

I am guilty of an 80 in a box for a couple of years, but it will be in a ARTF for next year honest....and if I ever get time I'll build the model it was intended for.

[Paul james 8]

Posted by Jon - Laser Engines on 18/11/2019 18:57:54:

For all enquires about cam timing ask Paul as he seems to have it right

I might give the washing powder idea a go myself. Many of the engines that come back for service are in a mind blowing condition and it can take half an hour of cleaning just to unearth the blasted thing.

Should your engine become a lawn dart at some point please do me a favour and give it a clean before sending it in. Im not an archaeologist and the next clump of mud i get back is likely to go in the bin even if there is a fossilised engine inside :P

Oh and while we are at it, if you never actually take a peek inside the cowl of your model and never clean your engine dont get all grumpy when i give you a large repair bill due to debris in the cylinder causing all sorts of damage. The two most common faults i see are bearing failure and debris ingestion. Both are caused by simple neglect and lack of maintenance. Its totally preventable and a little pro active maintenance is well worth while. Sending it back after metal flakes start coming from the exhausts is too late, its already broken!

Perhaps i should start a rogues gallery of neglected engines and the horror within?

Well that bit about the valve timing is very decent of you BUT....it is because you explained to me how to set it up! LOL

They are easy to work on and I like the design, the position of the carb can make them a bit tricky to fit in some models but it is possible to make up curved inlet tracts which can help.

If you do end up with any clumps of mud, feel free to fling them in my direction for resurrection Jon, I do actually have one in my collection that was given to me as the bearings were well and truly shot.

I'm not sure why some get cross about those of us who rescue and refurbish them without immediately putting them to use, many wold just be left as scrap unless we did put them right. I've got a Flair Bristol F2b that is on my project list, that will take the older long stroke 90 and be great on that, I've got a 75 that I plan to fit into a new ARTF Acrowot but a host of other models half finished with others needing their maiden (post refurbishment) flights.

[Paul james 8]

Here is one that I got which didn't have a carb so I made up a new inlet stub and modified an Irvine carb to fir, runs very sweet

[Paul james 8]

An old 90 refurb, bearings really bad, all very dirty but soon sorted out, marks on the piston crown where the valves had touched but thankfully neither was bent and it all went back together.

Bearings!!

Both of these are 90's, the bigger one to the left is an earlier, longer stroke model.....

Edited By Paul james 8 on 18/11/2019 23:15:18

[Ron Gray]

Hey Paul, there’s some dirt on the exhaust on the one on the right.

[David Davis]

Posted by Chris Walby on 18/11/2019 21:23:13:

The rogues gallery should be a list of people who have bought engines and are not using them.

On an annual basis owners should declare the number of hours the engine/s have run and if not sufficient then returned to Jon for resale.

I am guilty of an 80 in a box for a couple of years, but it will be in a ARTF for next year honest....and if I ever get time I'll build the model it was intended for.

I plead guilty to owning eight m'lud: a 62, three 70s, an 80, a 90, a 150v and a 155, none of which are currently installed in a model in flying consition.

In mitigation, the 62 or one of the 70s will be installed in the Big Guff I am building; another of the 70s will go into an ARTF Acrowot; the 80 will go into a DB Sport and Scale Auster which only needs the fin, the rudder and the struts to be built and covered and the 150v is already installed in a WOT 4 XL which needs a recover!

[Jon H]

Paul your short 90 is actually an 80, or perhaps a very late 75 like your other example.

The 80 was just a bored out 75 and the 100 was a bored 90. A simple check is to see if the piston from the 90 fits, if so its a 75, if not its an 80

I was trying to see if there was anything stamped on the mounting lugs that would give a date of mfr and help pin down the size but the photos dont show it.

[Paul james 8]

Posted by Jon - Laser Engines on 19/11/2019 08:26:07:

Paul your short 90 is actually an 80, or perhaps a very late 75 like your other example.

The 80 was just a bored out 75 and the 100 was a bored 90. A simple check is to see if the piston from the 90 fits, if so its a 75, if not its an 80

I was trying to see if there was anything stamped on the mounting lugs that would give a date of mfr and help pin down the size but the photos dont show it.

Interesting comments Jon, I put it down to be a 90 as I carefully measured both bore and stroke while it was apart for refurbishment and it came up at 90?

Could it be an experimental one perhaps?

Edited By Paul james 8 on 19/11/2019 09:23:46

[Chris Walby]

If in doubt measure the bore and stroke and calculate the volume, job done!

[Paul james 8]

Posted by Chris Walby on 19/11/2019 10:01:05:

If in doubt measure the bore and stroke and calculate the volume, job done!

Erm, that is what I did.

[Jon H]

If memory serves the calculation for capacity is pi/4 x bore^2 x stroke.

Our 90, 100 and 150 all share the same stroke and just had a variety of bores. The same was true of the 75, 80, and 120.

The smaller engine cant be a 90 as the crankshaft will not physically fit in that crankcase although the 85 and 90 share a bore as do the 80 and 100.

So if we assume you got to a capacity of .9 by multiplying bore and stroke in inches to get

Capacity = Bore x Stroke

Stroke is constant so we get

.9 = B x .87

Work all that out and bore is 1.03 inches.

If we ignore all the rounding errors that is pretty close to the 1.04 bore size of a 75 and 90. An 80 has a bore of 1.09.

If we go back to the start and calculate capacity..

3.142/4 x 1.04^2 x 0.87 = 0.739 cu/in

call that 74 in reality but 75 sounds better for marketing

If so you have a pair of very late 75's as we didnt do many with the clips holding the carb and exhaust in place. Either of those, or the real 90 would pull the bristol without any trouble.

 

Now, time for a lie down after all that maths  

Edited By Jon - Laser Engines on 19/11/2019 10:29:01

[Paul james 8]

I've always used pi r squared x height for volume of a cylinder, I am intrigued now so will have to take the head off and measure again. Lol

[Chris Walby]

Well at least its not a twin overhead cam, chain drive with vernier cam wheels, V twin, oh the fun! LOL

Edited By Chris Walby on 19/11/2019 10:49:15