Laser Engines - Technical questions

[alan p]

Like the catcher not good if that dropped in the swarf tray😒

[Jon H]

13 minutes ago, alan p said:

Like the catcher not good if that dropped in the swarf tray😒

 

most of them do unfortunately. Some poor soul has to rescue them

[Engine Doctor]

Why start with a bar so thick ? Just made a couple for an old 75 and PTFE  can be bought in much smaller diameter . Seems a bit wasteful ? Or is the video a clip off of youtube ?

[John Rickett 102]

Here's a lesson for Laser lovers. If you change the bearings, make sure the screws are fully tight and use plenty of Loctite.

I'd changed the bearings about 10 flights ago (for stainless ones) and all was well until a noise developed immediately after take-off, the immediate plan was a tight circuit and land but there wasn't enough time before the front housing departed.

As luck would have it, the housing was found. The crankcase is a bit of a mess though the bearings and housing seem fine. There is a score on the crank pin, its probably not done much good to the conrods either.

Fortunately, a fellow club member has offered another twin that he's had sat on a shelf for some time, so the situation is recoverable.

The cowl was lost to the wheat crop, that will take the longest to remake.........apart from that it was a nice day yesterday.

 

    

[Jon H]

14 hours ago, Engine Doctor said:

Why start with a bar so thick ? Just made a couple for an old 75 and PTFE  can be bought in much smaller diameter . Seems a bit wasteful ? Or is the video a clip off of youtube ?

 

No its our video. The bar is that size as we do a larger diameter job (the rocker spacer) from the same material at the same time and it saves breaking the machine down and resetting all the chucks. That said, the boss did mention he wasnt able to get hold of the normal stuff we use and had to go larger as there are shortages of everything at the moment. 

 

Realistically these should be injection moulded. The initial cost for that is high, but over 40 years we would have more than made it back. If anyone ever invents time travel i will pop back to the 80's and mention it!

[Jon H]

1 minute ago, John Rickett 102 said:

use plenty of Loctite

 

Please do not use loctite when assembling engines. I get engines back with loctite on the screws all the time and its infuriating as it takes forever to get them apart. I also have an allen key grave yard in my scrap box thanks to loctite in engines and I regularly have to drill the heads off of bolts to get them out once my allen keys have been murdered. NO LOCTITE!! 

 

Done up properly the engines will not fall apart as the ali parts expand more than the steel bolts so the whole lot pulls together when hot. This assumes of course all of the bolts are tight in the first place. Normally at least 2 need to be loose for this sort of failure to occur. The front housing rattles about the and remaining threads are stripped from the case. 

 

If you need it repaired John pop it back to me. If the rod bushes are done we can replace them and dress the crank to tidy it up. It should be no problem. I am off today/next week but i can get into it when i get back

 

 

[J D 8]

    Plus one on the above for locktite. I replaced a bearing in an early RCV 60sp many moons ago and the whole cylinder housing came loose.  It remained together but cylinder gear ring was damaged.

  I understand Jon's dislike for Locktite above, come across the issue myself.  However this is often due to the wrong type being used. 

Blue Locktite for items to be removed again and Red Locktite for those that need to stay put. [other makes have different colours which causes confusion]  

 Blue Locktite also helps prevent corrosion in the threads.

Heat is your friend when removing screws/bolts Locktited in, Blowtorch for big, pencil flame for small and for the tiddlers a soldering iron on the screw head for a bit.

[John Rickett 102]

Ok Jon,

I understand - No Loctite.

Thanks for the offer to repair, I'll probably accept that as, apart from the damage to the crankcase front face and seating area for the O ring, the rest looks like it can be overcome with a bit of skill - it would be a shame to scrap the engine if redeemable.

I'll see what the condition is of this other engine, I guess it could do with the bearings also being replaced as its been used and has been sat around for some time.

 

As a matter of interest, how tight is tight when tightening the screws into aluminium?     

[Jon H]

I rebuilt an rcv 120sp and have not had any issues with it falling apart with no threadlocking of any kind. If screws are coming loose they likely we not sufficiently tightened to begin with. 

 

8 hours ago, John Rickett 102 said:

As a matter of interest, how tight is tight when tightening the screws into aluminium?     

 

Depends on the aluminium, and bolt etc. I just do 'em up!

[Mike Mc]

Compression Ratio?

 

In the US were having a conversation about the compression ratio of various 4-stroke engine. Just curious about the compression ratio of Laser engines. I have a new 70 and a FT160 and FT200.

 

Has the compression ratio changed much over the years?

 

[Jon H]

Every engine has a different compression ratio as we only have two bore sizes and just keep adding to the stroke. The 70, 80, 100 and twin derivatives share a bore, head, cam timing etc. Its the same for the 120, 150, 155, 180 and twin's derived from them. Old 120's and 240's had high compression heads, but we stopped that as it made no real difference and was just another part to make. 

 

I do tweak the squish area a bit to adjust the c/r on some engines, but i do not have it calculated and worked out. I just know that 100's run better with 40 thou squish rather than 30. 180's run about 40, 155's nearer 30, 70's 30 etc. +- 5 thou makes very litter difference mind you. 

[Paul De Tourtoulon]

Going into politics, Jon ?.😄

[Jon H]

52 minutes ago, Paul De Tourtoulon said:

Going into politics, Jon ?.😄

 

Crossing the international punchline there Paul. No clue what you are talking about im afraid

[Paul De Tourtoulon]

7 minutes ago, Jon - Laser Engines said:

 

Crossing the international punchline there Paul. No clue what you are talking about im afraid

Mike's question was

 

" Compression Ratio? "

[Jon H]

yeaaa...and i answered him..

 

[Chris Walby]

Paul and Mike, if you really want to know then measure it, if not take the subtle hint that the manufacturer does not feel its important for you to know.

 Its a pointless discussion without knowing all the other factors that go into producing a powerful and reliable engine.

 

Fuel, tune and fly...then repeat until you have worn it out, good luck 🤣

 

 

[Ron Gray]

3 hours ago, Mike Mc said:

Just curious about the compression ratio of Laser engines

Enough.

[Paul De Tourtoulon]

Here we go again,🤢 another Laser engine owner looking for what he has just got hold of, this time on fb, It would be nice if Laser engines addressed this problem of identifying their engines, a page on their official site with the dimensions and weight of their engine's would stop this never ending list of 'what is it ?' might stop.🤢

 

[Eric Robson]

Paul,If you click on the engines on the Laser website all the information is there for all current engines

[Martin Harris - Moderator]

As far as I'm aware, Jon addressed this problem several years ago and new engines are stamped with their capacity.

[Jon H]

2002 laser 150 with metric crank. I was still at school when that was built so why are you yelling at me like its my fault? 

 

 

 

 

 

[Paul De Tourtoulon]

6 hours ago, Eric Robson said:

Paul,If you click on the engines on the Laser website all the information is there for all current engines

It isn't for me, it's on the Laser fb site, all the older engines, still it does keep the forum alive,,,😄

[Paul De Tourtoulon]

49 minutes ago, Jon - Laser Engines said:

2002 laser 150 with metric crank. I was still at school when that was built so why are you yelling at me like its my fault? 

 

 

 

 

 

Your name wasn't mentioned, unless you are the boss.

[Jon H]

13 minutes ago, Paul De Tourtoulon said:

Your name wasn't mentioned

 

Seriously? That's how this is gonna go is it. Just own it Paul, your meaning was clear. 

[Martin Harris - Moderator]

Let’s not fall out over this chaps.  Jon is Mr. Laser as far as production, development and support is concerned but he’s an employee who has taken on the mantle after the effective retirement of the co-founder/owner. 
 

We’re lucky that Jon is interested enough to answer enquiries about defunct products - there’s not much information (i.e. nothing) on the car I bought in 2002 on its manufacturer’s website - I also doubt that a full range of spares are available from them too. 
 

I do appreciate that Paul is suggesting that a web page identifying old models could save Jon some enquiries but I suspect that it wouldn’t be as simple as saying look for a couple of dimensions or fittings to confirm it’s a 1990 Laser 62 or a 1993 70.  Cataloguing and publishing every change and variation in a useable format is probably a far more complex task than using personal experience to answer the occasional query?