one of bob shores engines

[chuck foster]

well i have been working on one of bob shores engines the last couple of days and i must say it has been a challenge for me. it is a model called the little angel. bob drew it up as a 1/2" bore 1/2" stroke engine. well i got inspired by a a guy i know by the name of bill huxhold to make it smaller (bill builds very small model steam engines).
so i thought i would just half all the dimensions. well that is easier said than done. since the smallest model i have built has a 7/8" bore and that is a far cry from a 1/4" bore. i have had think in a whole different way, like how to hold some of the smallest parts and how to drill and tap 00-90 holes!
i have included a couple of pics to give you an idea of what i have been up to.

the first pic shows the engine frame or base with a lighter for comparison.

the second pic shows the base with the gears and a #0 center drill for comparison

the last pic shows the intake valve beside a 0-80 x 1/2" long cap screw, the valve stem is 0.032 in diameter

i'm sure many of you fellas out there have done something this size and i would like ideas on how to tap 00-90 and smaller holes. i have never taped anything smaller than 0-80 and i just know i will need help,so if you have any suggestions tips tricks or tools to make this job easier i'm all eyes and ears.

thanks
chuck

 

[zeusrekning]

Chuck you must have small nuts!

 

[Jadecy]

That looks like a very interesting project and some very interesting engineering challenges. Please keep us posted on how you decide to handle the scaling issues.

I talked to a guy at Cabin Fever that told me that the little angel was originally built in three scales by Mr. Shore and that the Little Angel plans was the smallest of the three.

 

[zeusrekning]

OK, I finally finished laughing. I came across a site a while back where the guy was making tiny scale models and he was very much into the accuracies of scaling everything. I remember him going into how he made his own taps and the difficulties he had. He even stated how many taps he went through per hole. I barely remember reading this, the only reason I do is his taps seemed so small you could barely see thread. Hopefully someone else may be familiar with the site I'm referring to b/c I don't remember.

What is the OD of a 00-90 thread?
Tim

 

[chuck foster]

00-90 uses a #62 drill and that is 0.038"
this will be a big learning experience for me, the last engine i worked on used mostly 10-32 nuts and bolts!

chuck

 

[DICKEYBIRD]

Holy cow! An .012 cu. in. 4 stroke engine? (Assuming my Jethro Bodine cypherin' and gusintas are correct.)

This'll have the 1/2A model airplane engine fanatics all wetting their pants.

I often dreamed of making an .049 4 stroke. If I can learn enough watching your project, maybe one day it'll happen.

Milton

 

[shred]

I typically tap 2-56-type sizes with a tapping block and a T-handle tap wrench with the handle removed, just turning the knurled chuck part with my fingers. I don't know how well that translates down to 00-90-- Somebody makes a 'sensitive tapping attachment' as well that might be worthwhile.

 

[cfellows]

Chuck,

Looks like a fascinating project. Wonder if there's any way you could make contact with George Luhrs. He's made some pretty tiny engines. Here's his web site: http://www.minimodelengines.com/

Chuck F.

 

[mklotz]

I showed these before but they're worth repeating here.

The tap guide second from left is the one I use for 00-90 taps. Shown below the guide is the collet for a 00-90 tap. The freewheeling 1/8" guide rod in the top of the tool is ABSOLUTELY ESSENTIAL when using such small taps. Grasp it in the chuck after drilling the hole so that you're guaranteed that the tap is aligned with the just-drilled hole.

Actually, something a bit lighter than mine might be better. Try making the guide body from 1/4" stock with a hole drilled to accept the tap shank (thus no need to make collet) and a 2-56 setscrew to lock the tap in place. Make the hole for the 1/8" guide rod a nice sliding fit - I used an "over" reamer - 0.126".

======================================================================================

Another random tip for your shop notebook...

The formula for the major diameter of a numbered screw is:

OD = 0.060 + 0.013 * N

where N is the thread number. Thus a #0 is 0.060", a #1 is 0.073", a #2 is 0.086", etc.

This formula also works for sizes smaller than #0. Simply use negative numbers for N, e.g.,

00 => N = -1 and OD = 0.060 - 0.013 = 0.047
000 => N = -2 and OD = 0.060 - 0.026 = 0.034
0000 => N = -3 and OD = 0.060 - 0.039 = 0.021

 

[chuck foster]

well marv i took your advise and made a small tap wrench like the one in your picture. ;D
all i have to say is any body using small taps should make one you can feel the tap cutting and every hole you drill and tap in one set up is perfectly straight and square.
i will be making the other bigger tap wrenches as i need them.

here is a pic of the wrench and 00-90 tap.

and here is a pic of the 00-90 bolt i made

i hope to get more work done on the model tomorrow, i spent some time today putting a digital caliper on my mill ( poor mans dro )


well again thanks marv and other esteemed gentlemen for all your help, i know i will have more questions as this project progresses!!

chuck

 

[zeusrekning]

Man i'm impressed. What kind of machine did you use to machine the bolts?

 

[Swede]

Wow! That is quite a project. Please be aware that IC engines in submicro scale can be very finicky when it is time to run them... getting good compression especially can be a challenge. Your parts look excellent so far, so if it can be done in that size, I'm suspecting that you'll be able to do it! Good luck! ;D

 

[AllThumbs]

Chuck,

Nice engine so far! I see you are a fellow canadian. Where are you? I am in Woodstock, Ontario.

Eric

 

[raym 11]

Wow!
I built the 1/2" bore Little Angle and I cannot imagine doing it @ 1/4" .
I fitted the piston (.562), without a ring to drag around. I also stroked it(+.062) and used ball brngs. It is a good runner. You might look at some of these mods.to optimize that little sucker.

Would very much like to stay informed of progress.

Ray M

 

[chuck foster]

i managed to rough out the carb. body tonight, still have allot of finish work to do such as lap the valve in and drill the mounting bolt holes. all in all it went good.
i got a bunch of those solid carbide micro drill bit off ebay and man do the drill nice. i got them from 1/8" down to .013", they should come in handy on this project.

these 2 pics are of the carb and valve, they look kinda rough but they are not finished yet.
the nut i used for comparison is a 5/16 x 18

zeusrekning:
you asked what kind of machine i used to make the bolt, i turned down a piece of brass to the right dia. then i used a die to thread it 00-99. i thought about cutting it on my lathe, then i though "who am i kidding, i can't even see to sharpen the tool bit"
my lathe by the way is a 1940's vintage 9" south bend.

Swede:
i admire your confidence in my machining abilities and thanks for the compliment. i have rebuilt about 25 or more of the full size hit & miss engines from 1/2 hp to 25 hp and i have noticed that as the engines got smaller carbration and compression get more critical.

AllThumbs:
ah another canuck!!! i live in aurora just north of toronto. do you ever go to milton steam show? if so we should meet there this summer.

raym 11:
now that you have told us about your engine can we see some pics and a video of it? ;D

again.....thanks guys for your positive comments and help with this project.

chuck

 

[Powder keg]

Wonderful job!!! I have a 9" Junior south Bend made in 1927. They sure are nice pieces of equipment. Do you use a magnifier on your lathe? I've been thinking of getting one of those with a goos neck and a light?

Wes

 

[AllThumbs]

Milton Steam show? Never been, will go if I can! Do they have a beer tent?

Eric

 

[raym 11]

Chuck Foster;
I apologise for running on about my Lil' Angel. I replied to your post with the intent of suggesting some design considerations for such a small engine, however I now realize I was 'preaching to the choir'. It won't happen again.
I am just a forward looking beginner.

I haven't tried posting my videos. Large files take forever to handle with this dial-up service. Maybe I should ask tattoo mike about it.
Ray M

I have posted this image elsewhere on this forum. The Lil' Angel is on the left.

 

[chuck foster]

i did some more work on this little angel. ;D
i made the water hopper and pressed a cylinder liner in and lapped it to 0.250"
i used a needle eye lap and it worked very well, i got a bunch of these on ebay for about $10.00
the set goes from 1/4" down to about 0.026" they seam to work well but i will know when i get the piston in and see if there is any compression!!!!
here is a pic of the little engine so far
i don't smoke but i always seam to have a cigarette light in by pics for size comparison

the round thing under the engine is one of the flywheels

along way to go but piece by piece i should get there.

chuck

 

[Mcgyver]

Chuck, that engine is really neat, i didn't appreciate how small it is until i saw it with all the reference items in the pics.

Seems like we're just about neighbours, I'm in Toronto.

So Eric, you're in Ted McJ's part of the world? I don't know much but went through his store/shop years ago. couldn't leave without a bunch of castings.....I've built the Rider Ericsson engine and am 90% through building his Perkins hit and miss engine. Are you part of the model engineering group that meets at his place?