MP Jet Letmo 0.6 Replica

Hello

Actually the tank is not bended, but just loose. And there's no trivial solution to thighten it back because the nozzle turns in the tank hole ! I think nothing is broken !

The NVA from the Classic MPJet cannot fit on this engine, because on the Letmo it's press fitted and screwed on the Classic (like a mills)

Vincent

Grosvince wrote:Hello

Actually the tank is not bended, but just loose. And there's no trivial solution to thighten it back because the nozzle turns in the tank hole ! I think nothing is broken !

The NVA from the Classic MPJet cannot fit on this engine, because on the Letmo it's press fitted and screwed on the Classic (like a mills)

Vincent

Well it would seem your only practical option would be to get a complete tank assembly for a Classic 040 from MP Jet, press out the jet from the top side of the Letmo venturi, fit the Classic tank top, and press the jet back in-using some kind of thread locker to ensure it stays put, as pressing it out will have loosened the fit slightly. As mentioned earlier-the Classic tank bowl screws onto the tank top, so there is no problem is reassembling the tank.

It won't be quite authentic for the Letmo-but it WILL allow the engine to be used.  If you had access to a lathe you could machine up a new tank top for the Letmo-thread part of the upper  OD of the jet piece closest to the hex or locating flange and screw the tank top in place on the jet-and then use the sidewall and base  portion of the original tank to complete the assembly-but you would have to destroy-or at the very least damage -the original tank top-in the process of disassembly. From the photo you posted I initially assumed that the jet portion had been bent, but in light of your second post I'd now guess that the original owner has enlarged the hole on the tank top by mishandling, and the entire assembly is now loose on the jet piece.

If you are exceptionally lucky and manage to get the tank apart without significant damage to the tank top-other than the enlarged central hole-I suppose it should be possible to fit a custom made rivet in this hole (which might have to be enlarged further to take it) and then drill this rivet to the original correct diameter to be a close fit on the jet, and press things back together as before.

A lot would depend on how thick the tank top material is-and how soft, as to whether this approach would work. From memory-and I haven't looked at my small Letmos for over a decade-the material thickness is fairly thin. If it was thicker i'd consider fitting a screwed bush rather than a rivet-but I doubt there is sufficient thickness to get an adequate thread.

ChrisM
'ffkiwi'

Hello,

Thank you for your advice, but the 2 engines are very different in many points, especially when it come to tank mounting/construction.

There's simply no easy way to put a Classic tank on the Letmo (as I own the 2 engines, I will take some pictures to clarify this).

Vincent

So do I -I own nearly two dozen MP Jets of all varieties-other wise I wouldn't have offered the advice in the first place. You asked for suggestions-you got them-I've provided you with a variety of possible options. You are of course entirely at liberty to reject the suggestions. I wait with interest to see what you will do in that case.

CJM

ffkiwi wrote:So do I -I own nearly two dozen MP Jets of all varieties-other wise I wouldn't have offered the advice in the first place. You asked for suggestions-you got them-I've provided you with a variety of possible options. You are of course entirely at liberty to reject the suggestions. I wait with interest to see what you will do in that case.

CJM

My apologies. You have right, the Classic tank fits on the Letmo carburettor. I must double check before to write.



Vincent

Now that you have established that-you have the option-should you want it-of fitting one of the enlarged Classic 040 tanks and getting a longer run out of the Letmo for R/C use should you desire that option. Obviously MP Jet realised some of the shortcomings of the Letmo and improved on them when they designed the Classic.....the Letmo tank set up is a right abortion of an idea-and the mounting not a whole lot better-nor the pressfit venturi-which is also on the big 2.5cc Letmo MP Jet replica.    I machined up a Cox Thermal Hopper type 'cage' mount to fit mine-both the 0.6 and the 2.5- for model use.

ChrisM
'ffkiwi'

Video showing homemade engine mount.

https://www.youtube.com/watch?v=icMDsIldse0&t=66s

Nice mount !

Does this engine runs well despite the shortcomings related by ffkiwi ?

Here in France rules are getting harder and harder for RC modellers, thus I will focus on small planes (below 800g) and this engine is a perfect fit for small oldtimers.

Regards,
Vincent

Grosvince wrote:Nice mount !

Does this engine runs well despite the shortcomings related by ffkiwi ?

Here in France rules are getting harder and harder for RC modellers, thus I will focus on small planes (below 800g) and this engine is a perfect fit for small oldtimers.

Regards,
Vincent

The mount is nothing special.
I went to the local hardware store and got the "standoff" nuts that are used for electronic boards for mounting.

Here are two Cox engines with the standoff nuts.






You should be able to do the same for the Letmo?