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ffkiwi -> RE: letmo 0.06 diesel (5/5/2012 2:05 AM)
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OK gents here's a comparison of both of them side by side-the 2.5 is wearing an 11x4, and the 0.6 an 8x4. The mount for the 0.6 is entirely my own effort-but the only logical way to do it-once you start cutting clearance holes in the front of models and THROUGH firewalls, you're setting yourself up for grief down the track.........far better to use a 'standard' firewall radial mount setup-especially and these engines vibrate a bit-the 2.5 especially!
The mount details (I made it a decade ago, when I had fewer machining skills than now, so its a bit rough!) are: standoffs 3/16" dia aly, 30mm long [you could make them shorter-but then you can't get a finger in to choke the engine!], tapped 2mm at each end. The flange is 1-3/8" dia Delrin, ~5mm thick, with the rear screwheads (skt hd) countersunk flush. There is an angled scallop filed in the top flange to allow easier finger access for choking.
A couple of words of warning to users-as I indicated a bit further up-both engines vibrate a bit. [due to totally inadequate counterbalancing, exacerbated by a heavy piston]. I haven't experimented with unbalanced props, which is sometimes a cure in this situation. What is a minor nuisance though, is that both have screw-in front housings, which can loosen up under vibration. You need either a custom made pin spanner [which AFAIK MP Jet don't offer as an accessory-though they'd have had to use one for assembly]-or a pair of special soft jaw pliers [which you can get from Micromark!.....see item #85161] to tighten it up. I've had the 2.5 come undone during bench running, but not the 0.6-though it remains a potential fault with the latter. Secondly, the venturi assembly is a PUSH FIT in the casting, it is not screwed in-so use caution if you need to re-position it in the event of side or inverted mounting-if you loosen the fit, you'll have no option but to glue the assembly in place-which is less than ideal! Thirdly-in the case of the 0.6, the tank is in three pieces-simply pressed together-again, don't loosen the fit!
Now I will revisit the 2.5 mount one day-with a view to milling one from solid Delrin bar-with a big U-shaped channel for tank clearance. I think this is a situation where going for a minimalist approach on the mount is not going to work. I did make one from aly rod similar to the 0.6 one shown in the photos, but can't find it at present to photograph it.
For Johnvb-I think a 12x6 is probably a bit much load-I use an 11x4 for FF and I'd use a 10x6 for RC as a starting point-I'd expect these engines to peak around 7000 or 8,000-so at 4,000 rpm on a 12x6 you're probably getting less than half the power the engine is capable of-unless of course you're flying Texaco or similar and going for low fuel consumption. My Letmos will be going on a full size 'Simplex' and the KK 1/2A Texaco Playboy respectively-in due course.........which at my current rate of building could be several years away..........
Otherwise I reiterate what the others have said-MP Jet produce great engines, to a very high standard, and from good materials-so they last. It's great that they have resumed diesel production again after nearly a decade of producing electrics.
ChrisM
'ffkiwi'
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