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Laser Engines - Technical questions

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Jon - Laser Engines07/06/2018 08:52:58
3957 forum posts
153 photos

Hi Trebor. something isn't right there as the pinion drive is not in the right place for TDC

trebor07/06/2018 10:31:41
avatar
1731 forum posts
213 photos

Well I'm stumped, it was easier fitting a replacement cam in the Landrover laugh maybe it rocked off TDC a bit before it moved the hight of my piston.

Jon - Laser Engines07/06/2018 12:59:40
3957 forum posts
153 photos

its much easier to do with the front housing removed. You can then locate and hold the pinion at tdc with your finger.

Joespeeder07/06/2018 17:43:00
40 forum posts
13 photos

Thanks Jon,

I had written a response late last night but when I went to post it I was timed out.... I gave up as I was on the iPad.

Yup, I have a lot of testing to do and I'll report what I see.

The Storch is a weird beasty. I've set it up per the guys in Germany flying the BH Storch. They cracked the correct CG for Storch like flight. There are many flying with a CG 30mm ahead of theirs but those fly faster and don't have that great Storch slow flight look as they go by. Never had a plane where I could show you videos with CGs 30mm apart and you'd think both are perfect at first look...

The German set up came from their forums and you're correct about the pitch speed. For now... I'm shooting for 50mph as top pitch speed. I will go down as needed. One of the German planes is set up as a tug also and they had a short discussion about the Storch not flying fast enough to tow. I can't see myself towing up too many Glass Slippers so I don't think that's an issue. Vintage wood wing gliders is what I'm setting things up for in this project.

Once I get this going I'm thinking I'll be able to idle around at lower rpms and have the extra speed as back up and if needed. I'll probably keep tuning till I get things matched.

More to come as I have anything useful.

Joe

Jon - Laser Engines07/06/2018 19:32:10
3957 forum posts
153 photos

I have found that many model manufacturers set the cg too far forward. They then use very large rates to compensate. Most of my models fly with c/g much further back and with probably half the control surface deflection.

With regards to pitch speed, my Stampe biplane has a max PS of 38mph at full power but as I fly it at half throttle most of the time its probably closer to 30mph in real terms.

Joespeeder08/06/2018 15:41:48
40 forum posts
13 photos

Hey Jon,

Yea, the issue with the Storch is the slats and as you're noting many of them are flying with too much pitch. 20x8 is common on lots of engines and motors. They rip around and can't get them to fly level at those speeds without going way forward. I think they may be overflying the slats to a degree that the slat becomes the leading edge of the wing. Their cg makes perfect sense if you count the slat as the leading edge.

I will probably end up closer to your 38mph.

The first videos you find when you google the BH Storch are kinda hard to watch. CG confusion and no rudder input when trying to turn.

The German set ups fly like your expect to see a Storch fly. THey do trim the ailerons down 3-5mm like a flap. The full sale dropped the ailerons (if I remember correctly) 20 degrees when the flaps were fully down at 40 degrees. Not sure if I copy the full scale or just do the 5mm as they did.

Hoping to test next week but next weekend I'm in the 7... smiley

Joe

Jon - Laser Engines08/06/2018 21:12:35
3957 forum posts
153 photos

cant say I disagree with you Joe.

I have seen the full size fly and it would fly insanely slow at high angle of attack. However, even when it was flying 'fast' it didn't fly level and always had its tail down a smidge. certainly it never flew with its nose down

Glenno6909/06/2018 11:37:14
6 forum posts
3 photos

G'day, From Perth Australia.

This is my first post to this forum, though I have been watching and reading and learning a lot.

I was recently given by a very good friend who quit modelling some years ago, now that he is flying his full size Flitzer Biplane, A Laser 100 engine and his scratch built Sopwith Camel.

The engine was seriously gummed up and grotty, ( he was using caster ) so I stripped it down to replace the bearings and De-carbon the valves etc. I am lucky to own several of the early engines such as 50, 61, 75, 90 and have rebuilt 2 or 3 of them with no problems. As well as a so far unused 80, & 150.

My questions are, I wish to remove the Rocker arm pivot pin to remove the rockers and the valves, there is a threaded screw between the rockers, which has a deep nut attached to take the rocker box retaining screw. Does this retain the pivot pin? and if so, how does one remove it, as it has no head?

Either side of the Rocker arms are a Teflon spacer one side and a rubber "O" ring the other, Is this correct? it seems to impart quite a lot of friction to the movement of the rockers, My early engines have Teflon spacers on both sides which allows them to move very freely with slight endplay side to side.

The Cylinder liner has a couple of sections of plating missing at the very top, When stripped, the engine was at TDC, so am thinking that the rings may have been stuck, Is this possible? I found no sign of the material when cleaning it though.

Hope I haven't been too long winded, and look forward to being able to return another beautiful Laser to the air

Many thanks

Glenn

Jon - Laser Engines09/06/2018 14:02:16
3957 forum posts
153 photos

Hi Glenn

The pillar nut has a stud on the bottom which holds the rocker shaft in place. Remove the nut with a small ring spanner or socket and it should all come apart. If the pillar nut has come off the stud then you might have to get a little more brutal and grab the stud with whatever you can to get it out. Don't break it off though as you will be in the poopy then. Once out, if its not too mangled clean it up and glue it back into the nut with stud lock. If its ruined, chop the head off an M2 screw of the right length and glue that in instead.

Your rocker setup is correct. O rings outside, rockers, then ptfe in the middle. We changed the outer ones to O rings as the original ptfe pads did not prevent oil leaking out when the engine was inverted and the customers complained...and I cant say I blame them.

grab a photo of the liner. Its rare for the nikasil to come off (twice in 25 years rare) but the old chrome ones would wear through after about 20 years of use. In either case its finished and needs a new liner.

Glenno6909/06/2018 20:10:33
6 forum posts
3 photos

G'day Jon,

Thanks for the prompt reply, I guessed that was the case, yes the pillar nut came off the stud. I did try using a thread lock to glue on the nut to the stud and warming the head with no luck, as you say I may have to try again, or get creative!

Will try a little oil on the rockers to lubricate the O rings.

Will try and get a photo of the liner, yes I intended to replace it and the rings, No problem though as the price was right. Have been making a shopping list, but via the forum I knew about your move, so have been holding off.

Glenn

Jon - Laser Engines09/06/2018 20:44:43
3957 forum posts
153 photos

If you have one of those micro blow torches you could hit the stud with a bit of heat to try and help get it out.

As for the move, its been looooong!

Glenno6910/06/2018 02:02:24
6 forum posts
3 photos

Jon,

Will give it a go and report back. Thanks for your help and support you give.

Cheers

Glenn

Glenno6910/06/2018 13:55:48
6 forum posts
3 photos

Hi Jon,

Success, I managed to remove the Rocker pivot retaining stud, I heated the head, not with my micro torch, but with my soldering iron resting on the head adjacent the stud, as I was concerned about damaging the rocker spacers. I was then able to grip the stud with needle nose pliers, and while the head was still hot, push out the pin.

Laser 100 Head

I also managed to get some pics of the liner,

Laser 100 Cylinder

Taken from the front of the engine, ie 12 o'clock. you can see the damage at 4, 6 and 8 o'clock

Laser 100 Liner

And in close up, You can see that it seems to correspond to where the top ring stops, at the top of the bore, Incidentally the engine may have sat for possibly 8 to 10 years since its last flight!

Glenn

Jon - Laser Engines10/06/2018 22:47:44
3957 forum posts
153 photos

is that not just oil crusted on? In the first photo you can still see honing marks, or is that where you cleaned it?

If its not oil then clearly its worn though and it needs a new fin barrel

Glenno6911/06/2018 10:08:18
6 forum posts
3 photos

No it's not oil, and the hone marks would be the original finish. The engine was mounted inverted in a F4c/FAI competition Sopwith Camel, so probably did very little work.

However it did sit unused for quite a while at TDC. the only explanation I can come up with, is that due to running caster, not flushing afterwards and then leaving it for a long time, is that the top ring may have stuck to the liner.

No problem, It's an easy fix, just wanted to share the info and get your opinion. After all to me it's an interesting and enjoyable part of the hobby as I also play with and race vintage motorbikes, so I can relate the information from one to the other.

Cheers

Glenn

Jon - Laser Engines11/06/2018 10:43:05
3957 forum posts
153 photos

No worries Glenn. In truth, you could probably run the engine another 5 years before it became a problem. I have seen liners much worse than that and the engines still ran fine.

Manish Chandrayan19/06/2018 20:12:28
465 forum posts
56 photos
Question for you Jon. Over at RCG on the Laser thread, discussions have veered to whether Lasers use a bronze seat for the valves? Current opinions are that earlier engines sure had the bronze seat but this had now changed where the valves are seated in head material. This was enabled due to change in material for the head.
What would be the current position regarding use of bronze valve seats in current product. I have not yet had an occasion to open up a Laser so can't check on any of my engines
Jon - Laser Engines19/06/2018 21:11:15
3957 forum posts
153 photos

Hi Manish

The old engines did have bronze valve seats but it was found they were not required. Once we hardened the valves in 92 all engines since have run their valves straight into the ali head. The type of ali we use work hardens nicely which is why we do not recommend a long cold run in process. Its very important to get the engine up to full temperature and with high rpm to make sure the valves bed in correctly

Manish Chandrayan21/06/2018 14:16:59
465 forum posts
56 photos
Posted by Jon - Laser Engines on 19/06/2018 21:11:15:

Hi Manish

The old engines did have bronze valve seats but it was found they were not required. Once we hardened the valves in 92 all engines since have run their valves straight into the ali head. The type of ali we use work hardens nicely which is why we do not recommend a long cold run in process. Its very important to get the engine up to full temperature and with high rpm to make sure the valves bed in correctly

Thanks Jon. That settled the debateyes

Chris Walby01/07/2018 07:17:06
avatar
599 forum posts
119 photos

Question for those with either Laser or WOTs WOT XL experience or both! I was just musing, nothing definite you know......well not quite yet...but the nights are closing in...

My electric WOTS WOT flies very nice, but I have never really forgiven it for the battery falling out and it is likely to become the winter hack so leaves a gap in the hanger, honest.

Would a Laser 155 (in stock) or a 180 (out of stock) be best suited for a WOTS WOT XL, Ability to climb vertically, but not prop hanging required. I am in no massive rush although its always worth having a few projects lined up..

Posted on this thread for obvious engine selection reasons, so please keep it directly related, thanks

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