Letmo 0,6 cc Replica Model Diesel Engine

Design History: The Letmo engine was originally designed and manufactured in Czechoslovakia in 1949 to 1950 by Josef Pfeffer in Brno. This replica engine is made and distributed by MP Jet Engines in about 2002.  

Design Features:
Rear induction;
side port;
plain bronze main bearing;
admission is by induction of the skirt of the piston and thus the direction of rotation is unimportant.


Specifications:
displacement, 0.6 cc  (0.0366 cu. In.);
bore, 8 mm diameter. (0.315 in.);
stroke, 12 mm. (0.472 in.)

Observations visual material by YouTube Channel valic000:

Here we have a replica of a well known Letmo 2,5 diesel made by the famous Czech model engine designer Josef Pfeffer. He made so many lovely and quality engines in the past in my home country. I can only say about MP Jet engine...very well made and with perfect finish and fits. I got a filled in guarantee card when I bought some years ago a 2,5 cc diesel from E-bay and that was a very nice runner. I must quit collecting as, I have all ready too many engines at this moment.... but this one was not expensive and free shipping and with extra tank and also prop...so I give myself a "green light"... for just this one last time....somewhere I will find a small space for him. I can highly recommend MP jet diesels. Great engines! Thanks for watching.

 

Extremely Rare Spanish Byra 1 cc Diesel

Special thanks to Peter Valicek (YouTube Channel valic000) for uploading this content.

 The first Byra was a side-port 5 cc .

Introduction:
The power full ZOM, and Llam engines are better known or also the competition engines from the Parres brothers.All very good performers! This little Byra engine I get some time ago,as the parts were present,but it was impossible to make it run because of the fits. There is not a lot known of the 1 cc version.About the others,special the 1.5cc and 2.5 cc bb versions is far more known,as there were also tested by the British modelling press. Its even possible,that the 1 cc make it only thru the prototype fase. The idea was,to have a counter part of the ED bee,which was a huge success sale not only in Britain,but all over Europe. There are no sale records of the Byra 1 cc.Strange enough were the boxes also all ready made. What my friend Jesus told me,the Byra 1 cc were poor performers and will be never a sale success, I do my best, to give the engine good fits and I think,with a 7x4 prop it will not really perform badly. How ever,its a cheap concept design,with the most interesting part the cooling head,with a semi bore cut out of it, to get the venturi drilled out. Why not put the venturi a bit further to the front? Well, that answer could only come Mr. Battlo himself could answer. He had enough know how to build engines. He was also a good speed and stunt flyer. In the Aero modeler there is a lovely plan of the Spanish build ME 109, maybe worth to give it a try to build? So I hope you like this clip of another rare model diesel engine. It was a big job, as always with some setbacks but that's worth it. And a big, big muchas graciac for Jesus Ortega Delgado. His help is priceless!!

 Circa 1954 the 1 cc appeared for the first time.
Possibly there are fewer than 10 of these little gems left if the world today.

 Right side view

 Rear 3/4 view

 Left side view

 Specifications:square volumetric design (bore and stroke both 11 millimeters); weight 69 grams.clockwise runner. 

 Parts to be fabricated to make her a runner are: a new crankshaft, matching cylinder and piston.

 Also two transfer channels need to be milled out in the crank case.

 The first task is to replicate the original cylinder liner.

 Sketch of the cylinder and porting. shown above and below.

 Cutting the ports.

 It was decided to make the boost ports at plus and minus 45 degrees from the center-line in an effort to improve scavenging..

 completed cylinders with their ports are shown above.

 A new shaft is made slightly larger to produce a better fit in the crank case, also the big end is firtted with a bronze bearing to improve ware characteristics.

 The new shaft is made with an integral balance weight to produce a smoother running longer lasting engine

 Finished parts ready for assembly.

 Finished engine ready for a test run

 Standard Byra 1 cc crankcase has a slot at the front for some unknown reason, possibly to facilitate drilling of the intake venturi.

Super Atom .99 Model Ignition Engine

 Famous American Model Engine Designer Ray Arden's 0.99 cubic inch spark ignition engine

 Original box  dating back to the early 1940's that contained the test engine.

 Specifications:

Bore 0.50 inches;

Stroke 0.50 inches;

Displacement 0.97 cubic inches;

Speed Range 250 - 17,500 RPM

 Test engine shown new in it's box.

 Front 3/4 view of the four variants of the engine shown above.

 Rear 3/4 view shown above.

 The most unique feature of this engine is the piston which incorporates a pressure activated valve to facilitate the flow of the combustion gases to and from the combustion chamber. This feature is explained later in a short video clip.

 Shown above is the side view of the oldest version of the engine with its circular exhaust ports. 

 Shown above are the elements of the external ignition system: high tension lead, coil, condenser and the low voltage hook-up leads.

 Shown above is a schematic drawing of the suggested wiring hook-ups for different applications: free flight, control line etc.

Another unique feature of this engine is the total absence of an needle valve assembly to control the fuel flow to the engine, instead there is a fixed jet and the mixture id regulated by a lever located beneath the crankcase.

Engine mounting setup for the first run of this new-old engine shown above.

The next two short video clips demonstrates the aspiration feature and running characteristics of this engine.

OS 48 4-C Surpass

I have several of these engines in my collection, at one time we were of the opinion that it should be the engine standard choice for my scale sport models.

This one was not running very well and a few flips of the propeller answered my question; the valve timing was off and would have to be reset before the next run.

I discovered this before: valve timing cannot be accomplished on surpass engines until the valve rockers and push-rods are removed are removed and the head bolts loosened, to allow the timing gear clear the cam follower. This is a very annoying reality with this design; since the timing operation is essentially a hit or miss task it usually requires several tries to engage the correct tooth; having to remove all those screws is most frustrating procedure indeed. 

As soon as the valve cover was removed we also discovered the valve gap was far too large (estimated at .090 - .120 inches): another reason why its performance was so poor.

Engine run after timing set-up and valve tappet clearance adjustment:



Watch another of my OS 48 4-C engines running after I had performed a rather unorthodox repair when it threw its connecting rod in flight and punched out the bottom of the crankcase.

OS 70 4-C Surpass Main Bearings Replacment

This bearing replacement was not the easy project I had envisaged. The years of float flying had taken its toll on the condition of this engine. There was a considerable amount of rust coating the surface of the steel components, such as the crank and cam shafts, making disassembly difficult to say the least. Removal of the propeller drive would have been near impossible without the application of heat from a pocket butane torch.
The valve rockers and push rods removal went without a hitch after removal of the single socket head screw, holding the assembly to the head.

 The hole in the crankcase that is specifically intended for the extraction of the wrist pin retainer, an essential step before the connecting rod and piston can be removed. In my case I used a dry wall screw to accomplish this extraction.

 Since picture taking was the furthermost thing from my mind when struggling with the disassembly of our rusty specimen I am showing pictures lifted from David McIntire's YouTube videos

The next step was to remove the cam shaft; sounds simple enough but after removing the cover it was found that the shaft would not move out. It took a lot of sweat and prying before we were convinced of what the real problem was; the timing gear was not clearing the cam follower, even though it was pushed back as far as it would go with the push rod guides in place.....so remove the head before removing the cam shaft.
The screws holding the head loosened one by one after much coaxing with the metric Allan key; taking particular care not to damage the hex slots or break the screws in torsion, which would seriously complicate the repair if that occurred.
With the removal of all screws the head lifted off after some prying with an Exact o knife, taking particular care as to not scratch or otherwise damage the face of the head mating with the top of the cylinder liner, since this is a metal to metal joint without any gasket to compensate for rough surface finishes.
The liner its self was separated from the crankcase, using the same wedging and prying action.
With the liner removed, the connecting rod big end could not be detached from the crank pin no matter what position of the pin was in.
It wasn't until I read the manual and watched a YouTube video several times did I realize that the wrist pin had to be aligned with the hole in the back of the crankcase and the wrist pin bushing gently pulled out with a dry wall screw, before enough clearance was established to wiggle the big end off the crank pin, so that the piston and connecting rod could be removed from the crankcase.
Once this was done it was a relatively simple matter to push back the crank shaft and remove it through the back side of the case.
With the application of more heat the big bearing was pushed back with a drift pin and removed from the back of the case and the forward bearing pushed out through the front.
The only other points worth mentioning is a reminder to remove the dust shields from the rear bearing and the back side of the forward bearing to facilitate better bearing lubrication.
Freezing the bearings and lubricating the case helps with the insertion of the new bearings, this part of the process went rather smoothly in this case.

Things did not always go as planned and the valve timing was a real bitch of a job due to multiple witness marks on the faces of the calm shaft gear. The marks were so small that they were almost invisible without magnification and because each side of the gear had marks, I put the gear in backwards on my first attempt at timing.

Engine User's Manual

Camshaft Timing Video
Credit https://www.youtube.com/user/rcdieselrc

Spanish Estate Engines

Spanish Estate Engines

1 webra mach 1 - 2,5 D RI 2 Taifun Zyklon #2078 - 2,5 D R/C 3 Taifun Tornado # 42736 - 2,5 D FI 4 Taifun Hobby #15793 - 1cc D FI 5 WB 250 D FI 6 Dooling .29 7 MAP3 #6815 -2,5 DRV 8 MAP3 #68140 -2,5 DRV prepared for silencer 9 MAP3#6893 -2,5 DRV 10 MAP3# 6861 -2,5 DRV 11 Rossi black head 15G 12 Rossi black head 15 G new 13 Enya 15d year 2004 14 Enya 15d 15 Brown Junior with flightwheel 16 O&R 60 #071598 17 Taplin Twin # B21 18 Mc Coy 19 19 Veco 19 R/C 20 Torpedo 201 #1824 21 OK .099 long fuel tank 22 OK .099 23 O&R 60 #030879 24 O&R .23 glow FI #495137 25 O&R 60 #055004 26 Browni-E .29 uncomplete 27 Mc Coy 29, old 28 OK 29 uncomplete 29 LLAM 2,5 D A2 caja original 30 LLAM 2,5 MK2 caja original 31 KMД #122559 new 2,5D 32 KMД 2,5D #121747 33 KMД 2,5 D uncomplete 34 KMД 2,5D venturi missing 35 STG 20 15D year 1970 36 PИTM 2,5 D #123 37 KMД 2,5D NIB #121844 38 KMД NIB #122148 39 ZOM 2,5D MKII #MA295 sin carburador 40 ZOM 2,5D MKII A2301 sin carburador 41 OS Max 15 R/C #631 MaxIII 42 OS35 MaxIII #A7457 43 Webra Bully 3,5 D R7C #5774 44 MVVS 2,5 D7 #675 45 Fox 29 tilted glow plug 46 ZOM 2,49 MKII #AA 009 47 ZOM 2,5 D MK IV ultima serie 48 ZOM #A 2199 49 ZOM MK1 #2196 carter corto 50 ZOM 2,5 MK III #A 4556 51 ZOM 2,5 MKIII #A6608 hay que soltarle el cigueñal 52 ZOM 2,5 MK III tapa carter atornillada 53 ZOM 2,5D MKII # B 3460 biela tocada 54 ZOM 2,5 D MKII # O 122 55 ZOM 2,5 D MK I 56 ZOM 2,5 D MK I, sin buje con carburador universal 57 ZOM 3,5 glow con silenciador y carburador de V/C 58 ZOM 2,5 glow incompleto 59 baja 60 MVVS 5,6G #544, R/C carburator 61 MVVS 5,6 G #83 with pressure inlet broken 62 Mc Coy 19 63 LLAM 2,5 D MK II 64 Thunder Tiger GP-07 .07 cu in 65 COKOЛ OTM 2,5 D # 23316 66 Mc Coy 19 uncomplete 67 FOX 59 68 ED 2,46 D 69 ZOM 2,5 MK III 70 PAYA # 667 con caja 71 ZOM 2,5 D MK III# C1 72 ZOM MK II #f 1410 73 ZOM MK III # A0421 74 ZOM MK III # B5824 75 Fuji 25S #2337 R/C with silencer 76 Super Tigre 60 77 O&R 23 78 MD Meteor 2,5 G 79 Merco 35 80 Cox 09 Tee Dee 81 BANTAM without carburator 82 ETA 15 MK 3 Elite # 368081 83 Fuji 15 IVG #10126 84 KOMETA MД5 85 Nelson 15 D RV #2771 86 Oliver Tiger CS chinese copy #s3 87 Cipolla Junior 1,5 glow 88 ED 2,46 D MK II Racer year 1953 #RH174A 89 Cipolla Junior 1,5 glow 90 WB 2,5 D uncomplete 91 Oliver Tiger MK IV # T 7076 with silencer 92 BYRA 2,5 D last production 93 KMД 2,5 D # 121795 94 MOKI 2,5 G fuel needle missing 95 Rossi 15 D RV cox carburator 96 Rossi 15 FI G combat 97 Cipolla junior 1,5G 98 Rossi 15 D RV, cox carburator 99 SuperTigre 15 RVD 100 SuperTigre G15 long ventury, needle missing 101 Rossi 15 FI G #158 C 102 Torpedo 09 G 103 O&R 23 G FI #500595 104 Silver Swallow 1,49 blue 105 CS 09 glow 106 MAP3 2,5D #68778 107 CS 09 D 108 Silver Swallow 2,47 black, uncomplete 109 MVVS 2,5 D RV #K85 110 MVVS 049 G #E 374 111 Moccera ̈Bosta ̈ from Argentina 2,5 G 112 Taifun Bison 3,5 G #2054 113 Taifun Bison 3,5 G #6849 uncomplete 114 BUGL 2,5 D RV 115 SASSI 15-II glow 2,5 FI#1389 116 MK 17 1,5cc D RV #8741190 117 void 118 MK 17 1,5cc D RV #8741013 119 MД 2,5 G Meteop 120 Super Tigre X15 FI SL TST glow 121 UKTБM 2,5 K TAИΘYH 2,5 G # 17212 122 Fox 15 glow 123 LLAM glow, schnuerle con silenciador 124 Cox 09 FI red carter 125 UCTKAM 1,5 glow KP-AC # 03911081 boat engine 126 Super Tigre G15 2,5 glow for F1C with brake 127 Super Tigre G20.15 G FI 128 Rossi 15 F1G wide venturi 129 KMД 2,5 D # 442645 130 void 131 MK17 1,5cc D RV #8741221 132 MK 17 1,5 D RV # 8021657 133 CS 1cc G, lot of spare pieces 134 Cox 049 RV (VV) 135 Cox 049 Babe bee 136 MVVS 2,5 D FI #245 N 137 MVVS 2,5 D FI # 304 L exhaust trimmed 138 Super Tigre X15 FI G 139 void 140 Cox 049 Babe Bee, with silencer 141 MVVS 2,5 D FI #C 198 142 MVVS D7 #1886 143 AME 2,5 G FI VN BB glow 144 LLAM 2,5 MK II 145 Veco 29 146 Veco 29 147 Cox 049, Tee Dee carburator 148 Webra Mach II S1 149 Super Tigre G20 15D, MVVS carburator 150 Webra 0,8 cc D # 52007 151 Webra 1,5 cc D # 52007 152 Webra Bully? 3,5 cc Diesel FI R7C #5773 153 ZOM 2,5 glow # A 148 154 rossi 2,5 G MKI? 107G 155 Webra Mach I, uncomplete 156 FORA 2,5 D 157 FORA 2,5 D broken carter 158 KMD 2,5 D # 122365 159 PARES RV 2,5 D 160 void 161 ZOM 2,5 MKI-A 162 COX 049 163 MAGNUM GP 10, boat engine with pull starter 164 Cox 049, white fuel tank 165 MDS 40 R/C #20041455 166 PICCO car engine 167 JIM WALKER 065 engine year 1955 168 OS MAX 10 FSR R/C year 1976 169 OS MAX 10 R/C year 1961-1964 170 OS MAX III 15 RC year 1961- 64L 171 OS MAX III 15 C/L 1961 172 OS MAX III 15 C/L 1961 61J 173 OS MAX 15 C/L 1955 61H 174 Webra 1,5 cc red fins 23445 175 OS MAX I 15, glow 1955 176 OS MAX 15, 2,5 cc glow 1955 177 Enya 09 IV glow uncomplete 178 OK CUB 049 179 Enya 30 BB R/C 180 HP 61F-RC 181 PИTM 3 bolts #89 182 MVVS 2,5 D FI R/SE 183 MVVS 2,5 D FI S/RE 184 ZOM 3,5cc glow #R 1757 185 OS 50 R/C 1963 uncomplete 186 JEMA1,5 cc? 187 Webra Mach II 188 ZOM 2,5 D largo 189 JEMA 2,5 D RV? 190 K&B 61 FI R/C 191 ZOM 2,5 D MKII 192 ZOM 2,5 MKI AA-349 193 ZOM 2,5D MKI D-217 194 Taifun Hurrican 1,48cc #76322
Interested parties contact: crockerdh@aol.com