My first engine build, Lobo pup 1.6

[Mitchg07261995]

Hello my name is Mitch, i am new to the model engine buiding scene. I am currently taking a prescision machining class at a local community college in my neck of the woods and I would like to make a Lobo Pup, hats off to the designer, this engine is sweet looking. I descided to start contruction yesterday with the center bearing housing and i asked my instructor if i could make it, he took a good look at it and said no because he does not have a .063 endmill but he gave me permission to build the rest of the parts on that page which are the front bearing housing, rear cover, center bearing, and the front bearing.
So far I have completed the Front bearing housing in the suggested 6061 aluminum, i am not sure if we have bronze for the bushings in my class though, would there be an other alternative.
when this is completed i am going to make a 5.3cc lobo pup for my model airplane that i am building in my garage work shop. It is a satyr, designed in 1943, plans for this plane can be found at http://www.airagestore.com/plans/rc-planes/old-timers/old-timer-satyr.html i think that a twin would look sweet on this plane
Ill call the new lobo pup, the Lobo Pup 1.5x, because it is 1.5 times the origional engine
Thanks, Mitch.

 

[GailInNM]

Hi Mitch and welcome to HMEM.
The Lobo Pup Twin is not a great engine for a first IC engine build. Like all compression ignition engines the fit between the cylinder and the piston and contra piston is not very forgiving. It will help if you have run a compression ignition engine before so you know what the proper fit feels like. On the other hand many people have built CI engines as their first IC engine with great success. Fuel is getting harder to get also. Purchasing Ether is being restricted world wide making it hard to mix your own fuel.

Don't worry about the 1/16 end mill for the center bearing support. The two 1/16 wide notches are only there to aid in installing the support in the crankcase.While difficult to install without notches to rotate the support when installing the size is not critical. They can just as well be 3/32 or 1/8 or anything around those sizes.

As far as building 1.5X Lobo pup I would consider building it as a glow plug ignition. The Satyr is of fairly light construction and the high compression of the CI engine might be too much of a load on that light of an airframe during starting. The engine could be built as either glow or CI with the only difference being the heads and they could be interchangable. Everything else would stay the same. I drew a glow head conversion and it is in the build thread, but is requires changing the cylinder. I think that it could be done without changing the cylinder but have not drawn it up to check it.

Same thing goes for the 1.6 cc version. If problems happen then it could be converted to glow with relaxed construction problems associated with reducing the compression ratio from about 18:1 to about 6:1 or 8:1.

I would try to stick to bronze for the bearings. It by far the best choice.

Gail in NM

 

[Mitchg07261995]

thanks for the reply Gail, i have located a web site were i can purchase a 1 foot section of 3/8'' bronze for about $15. If i do build the bigger version of the Pup, i will go with glow ignition, because the fuel is more available, and because of the air frame issue that you brought up. I am enjoying the build, and i am thinking of starting the build of the crankcase sometime with in the next 2 weeks thanks, Mitch

 

[GailInNM]

Mitch,
You will want something larger than 3/8 bronze. The center bearing is 7/16 OD so you will probably want to start with 1/2 diameter.

Since you are considering building a 1.5x engine also, I would order a 5/8 diameter instead. A foot of it would be enough to make all the bearings for both versions with some left over. SAE 660 bronze is also known a CDA932 and as it comes as a cast section it is oversize. The 5/8 that I have measures about .658 diameter so could be turned to .640 diameter which is a standard fractional reamer size and is a little bit under what 1.5x scaling would be for the center bearing. Certainly it would be an acceptable size.

Lots of online sources. I mostly use Speedy metals, but there are several suppliers and I check them all for the lowest price. Here is a link to Speedy's round bronze.
http://www.speedymetals.com/c-8383-932.aspx

Roughly where are you located. Makes a big difference when ordering metal as shipping can get expensive because of the weight.
Gail in NM

 

[Mitchg07261995]

thanks for the link, when i do order the bronze, i will probably go with speedy metals because there price is less than what my teacher suggested (mcmastercarr) they want $33 for a foot of 5/8 bronze http://www.mcmaster.com/#standard-bronze-alloys/=k6yd1q Gail, thanks for suggesting getting something larger than the finished diameter

 

[AussieJimG]

Welcome mitch95, it looks as if you are off to a good start and with great advice too. It doesn't get better than that.

Don't forget the video when it runs.

Jim

 

[Mitchg07261995]

i will get a video of it when i am done with the engine, and ill try to post some pictures of my works in progress when i find my camera

 

[Mitchg07261995]

i attempted to make one of the cylinder heads for the lobo a couple days ago in class, everything was going perfect, I had completed the bottom end of the head and all i had to do was drill, tap it for a 10-32 screw then part it off, When i got to tapping it was going fine then the tap broke

 

[Mitchg07261995]

No progress to show this week because I had the week off from school due to thanksgiving, ill post my progress on monday