Hoppers and Bugs

Cool Deal Charles , looks like you got all the parts for 4 engines ! Enjoy the new to you engine and less beer money That's pretty cool that you would find the engine just as Charles is upping his game Ken . The only Hopper i got is like New ,never ran so it will stay that way $$ Till I can get another that's a runner or

Ken Cook wrote:          In and around 1982, I had a Space Hopper which was in a speed pan given to me. I have the pan still but I couldn't find the engine. I searched and searched for it for years. Last night, I opened this small gold tin can I knew I had, inside was the Space Hopper. I was pleasantly surprised. Locked solid ready for a tear down. Removing the rear screen cap over the intake is a bit of a challenge because the newer wrenches don't fit it. The small jet holes in the venturi stack are even smaller than the holes on a TD venturi. Sourcing a extremely small piece of copper wire was a bit of a chore last night but I managed. Unfortunately, mine has now what looks to be fuel and oil staining on the case and spinner. I was going to run it last evening but sundown seemed to take place in minutes.

How COOL .. My mom has given me several "tins" that I utilize in different ways.. but some can easily become stashed-away and forgotten about.

I know very little about about either of these two engines. The only Cox engines that were in my family, were sourced by my dad in the early 70's. "Bee" engines.. is all I owned for Cox engines.. until eight or nine years ago.

The above photos that show the parts-breakdowns are useful knowledge for me. Thank you for sharing Charles.

Nice rescue operation in progress, Charles.

Looking forward to seeing your final results, restoration to life again and any run reports.

gaskets and tiny bolts ordered. almost everything else is cleaned up

i need to figure out 2 prop-drive plates

Cleaning the venturi jets? the leeeetel beeety holes?
I grab a pliers, and YANK! a single strand of brass from one of my wire brushes,
then I use magnifying glasses, and use te brass wire to gently poke through and clean up the holes, with copious amounts of Ballistol to keep it all clean and lubricated

when mostly clean, I used compressed air to blow out the needle seat area, as well as pressurize it all and make sure air is flowing through everywhere it should

for these, I did not want super polished shiney, so I went with hours of gentle hand brushing with brass wire brush, ballistol, and rags. its looking better and better. Now waiting for gaskets from Bernie, and maybe some other bits and pieces

Drive plate is the only missing bits for 2 of the engines. and ONE of them is gonna have a "modern" cylinder/piston/head. but three of them have the originals

cstatman wrote:gaskets and tiny bolts ordered.   almost everything else is cleaned up

i need to figure out 2 prop-drive plates

Drive plate is the only missing bits for 2 of the engines.   and ONE of them is gonna have a "modern" cylinder/piston/head.   but three of them have the originals

My friend has a small lathe... a Unimat and another small/popular/milling machine in his basement/cellar workshop in his home. You may consider placing an ad in/on your local "community-board".. asking about machining services for a small (sub 1") one-off part.. made from Aluminum. There are people that would want to help you with this. You have drive-plate examples? If so; you could easily have them made to the exact proportions.. through an inspection by the machinist.

There might be someone in the next town.. down the road.. or even next-door.. who could and would make your prop-driver plates. They may even have some round aluminum bar-stock for the job. People helping people... It does still happen.

i have a TAG micro-lathe
and also have dear friends who are machinists.
these driveplates are tiny and intricate. I could make the shape, but it would be rough
the three slots that key it to the driveshaft (like a vintage O&R) are the difficult part to cut with precision
time = money

this plate, like .010 crankshafts, calls for "precision machining". most shops don't do tiny bits, and any precision shop is only interested in production quantities. The quote I got for .010 crankshafts was a minimal run of 500, and $27/unit.

thus? if i can find 2 of them? much cheaper than trying to make them.

want to love the idea of 'people-helping-people"
just like the bride to be asking a wedding photographer for cheap rates cause they will get "exposure"?
its difficult to ask my machinist friends to work for free.

3 cleaned and close
#4 needs crankshaft
#3 & #4 need driveplates

gonna try to spark off the 2 ready to run this weekend

Gents even if the driveplate is made on a lathe, how do you add the serrated contact surface for torque transmission to the prop?

balogh wrote:Gents even if the driveplate is made on a lathe, how do you add the serrated contact surface for torque transmission to the prop?

You can do like what I do to the electric motors I have when I use one of those shaft adapters to install a prop on it.
Those shaft adapters (when you purchase the cheap ones from China) don't have the knurling but have a smooth face.

I cut from 360 grit sandpaper a small disk to fit on the prop driver.
One side facing the prop and the 2nd one facing the aluminum prop driver.
The sandpaper gives enough friction to tighten up the prop to the motor/engine with no problems.

sosam117
Mike

imma try to get one or two on a test stand and running as soon as I can.

i am not gonna spend time and lathe work trying to build driveplates. either I find some, or they are display motors.

i need to dial the needle, and tighten my stand, it was bouncing a bit, but running

https://www.youtube.com/shorts/gT8OTn6ju9w?si=KItEgczlFF7boIqA

maybe go on a nostalgia class FF bird...

cstatman wrote:i need to dial the needle, and tighten my stand, it was bouncing a bit, but running



maybe go on a nostalgia class FF bird...

That Thermal Hopper showed potential. Would be a good add to any vintage C/L, F/F, or R/C. (Shoot, nearly every plan we show planes of now is over 40 years old or vintage )

balogh wrote:Gents even if the driveplate is made on a lathe, how do you add the serrated contact surface for torque transmission to the prop?

Easy-you do that with a knurling tool-which is simply a small piece of hardened steel anywhere from 5/8" to about 1" diameter, pivoted on an axle which forms part of the tool shank-so the knurl can freely rotate. Cut on the periphery of the knurl is a series of closely spaced V-shaped 'teeth' (think of a gear about 3/16"-1/4" thick with very fine teeth.....and you basically have a knurl)-these teeth can be parallel to the rotating axis or at about 45 degrees

In practice the prop driver blank in held in the lather chuck, rotating, and the knurling tool mounted in the normal toolpost and advanced axially into the spinning face of the prop driver, which leaves a radial knurl pattern with the radial grooves matching the teeth on the knurl. This is a metal DISPLACEMENT process not a cutting process, so it is usual to do it in several stages, brushing away any chips as they form to keep the face clean.

The same process can be used to produce the splines on the crankshaft-though this time you would bring the knurl in from the side, at 90 degrees to the spinning shaft. Sometimes-in the case of very small parts, you might want to use a knurl to make a thinner copy of itself so you can get the thinner one in to the job-in which case yo would knurl a cylindrical piece of soft steel bar, bore the pivot hole, part it off and then harden it. This approach often has to be used where a prop driver has a centre boss on it, which projects forward of the knurled driving surface-if you're trying to replicate one  of these you run into clearance problems with the normal knurling tool.

Finally-there are single and double knurling tools-the double ones are like a two tine fork-with pivoting tines each holding a knurling wheel-which on these tools are usually of the angled type-but with opposite directions-and the two wheels straddle the rotating work and are brought in contact with it from above and below by tightening a screw. the two knurls then each imprint their respective pattern on the workpiece-and since the 'teeth' are opposite handed-the result is the nice diamond pattern knurl you find on all sorts of tools and pieces of equipment-for either decorative or improved grip purposes.....in our case, frequently seen on needle valve knobs. I have both types of knurling tool-but mainly use the diamond pattern two wheel one...funnily enough for making grips for the rear peg on rubber models more often than engine parts.

Ooh-before I forget-another clever feature of face knurling-if the tool is exactly on centre of the lathe axis you get a true radial knurl-if it is set above or below centre-you get the attractive spiral knurl seem on many of the better quality Japanese and Italian model engines.

ChrisM

Thanks for the explanation so this is rather an extrusion than a cutting/milling process..in lack of the knurling tool one may just want to extrude or cut a few parallel grooves into the face, that would also help transmit the engine torque onto the prop..it is true though the radial knurles would keep the prop fixed even if it jumped a notch, but the parallel grooves, once skipped, would not hold the prop anymore before the prop slips 180 degrees..

balogh wrote:Thanks for the explanation so this is rather an extrusion than a cutting/milling process..in lack of the knurling tool one may just want to extrude or cut a few parallel grooves into the face, that would also help transmit the engine torque onto the prop..it is true though the radial knurles would keep the prop fixed even if it jumped a notch, but the parallel grooves, once skipped, would not hold the prop anymore before the prop slips 180 degrees..

No I wouldn't call it an extrusion process-extrusion implicitly means stock is forced through a die and the product has the external profile of the inner shape of the die. Knurling is a displacement process-softer material (you can't knurl something that is harder than your knurl is..!) is pushed out of the way of the teeth of the knurl-leaving behind a mirror shape of the tooth. The process is more akin to 'flaring' a piece of piping so that another piece of the same size can fit inside the expanded area-there knurling pushes part of the softer material of the prop driver out to either side of the tooth in contact with the surface-and since the work is rotating you end up with a series of peaks and hollows formed....with a bit of mess (because of the radial speed) at the outer side of the prop driver-which is usually cleaned up by taking a bevel cut on the extreme outer edge of the prop driver after the knurling is over-just to make it look a bit tidier. Other tricks include machining the blank to have an annular band on the front face-slightly raised above the overall surface-and just this band get knurled, not the entire face-which usually results in a better appearance....the German Taifun engines used this approach in most of their range

I think there are multiple ways of achieving the result-and knurling is a technique that has been around much longer than model engines, and usually for providing a gripping surface on metal items-so from an production engineering viewpoint it would be a logical way of doing things.,,, but you could also achieve a gripping surface by simply keeping the lathe stationary, and using say a threading tool-which has a V-shaped cutting profile-and winding this across the face of the prop driver blank-by rotating the lathe by hand a small amount, and repeating the process, you could generate a set of radial grooves on the driver face-and if you had a dividing head involved, you could move the work a repeatable angular distance for each groove [but dividing heads are fairly expensive accessories]

You could also-as seen on some-mainly Czech motors-machine a series of parallel grooves across the face-this COULD be done by using a vertical mill-but is most likely done using a 'ganged' tool-in the same way cylinder fins are cut-in a non CNC setup.  My very first prop driver-made almost 35 years ago-long before I had a lathe of my own-was for a British Mills 1.3 diesel-and done by the manual 'winding a sharp lathe tool across the prop driver face' technique. It wasn't pretty to look at-but it did the job....

ChrisM

Actually the hardest job with prop drivers is not the drive face it is getting the tapered hole at the back to exactly match the taper on the crankshaft-or-if a tapered collet is used-getting the collet male taper and the prop driver female taper to match....male tapers are easy-you just set over the compound slide....female tapers....not quite so easy-for a start-you have trouble getting a tool in there-most are too big, and if you happen to have a suitable sized miniature one-they are so thin in the shank that they flex whilst cutting-so again your taper doesn't match. The only safe way is to make a tapered D-bit reamer....and then you have to be able to grind accurately....

its that female taper. 100% keeping me from wasting my time trying to make this. I will never get it properly built