mikenlapaz

I put one of Ralph's converted 26cc on my Xmas list, but the local elf just smiled and said, "Got a second choice make me a list........."

Searched the electric catalog, made the list and placed the order. Well not quite like that I had the ported head kit on hand and wanted to use it.

The before cutting, ignition, and prop hub the weights totalled 35.6oz (1024g)

I need standoffs and would appreciate so input on studs. The threaded half of case has 12mm of unused thread in each of the m5 tapped holes. My thought is to install the regular case bolts, drop a small diameter spacer in hole and screw in a section of cutoff M5 bolt leaving 1.5x diameter (8mm) exposed for threading standoffs. Picture show Permatex Green which may be overkill, red high strenght may suffice.

Need to fabricate a twister manifold. I have both 3/8" and 1/2" G10 Any recommendation or preference? Ralph??

I Walbro WT668A , 12.7mm venturi came in the box. I have a CH Ignition on hand.

mikenlapaz

We see lots of conversion but not very many built from parts Zenoahs.

mikenlapaz

The one pic shows first idea on stud install. What grade bolt would be preferred for making a stud for this application?

Antique

My Feedback: (4)

Looks like a very good start...The 2 bolt cylinders work very well on airplane engines..Metric grade 12.9 is equivalent to US grade 8....Anything but standard hardware low grade stuff will work well...
3/8 G10 is what I use on all conversions, no need to use the 1/2..
Another way to make a mount is make the back surface of the case flat, drill the case bolts all the way through for 5mm or 10-32 bolts, then use a 1/4 aluminum plate, threaded for the long bolts, for the mount to hold it all together...You can make a big hole in the center of the plate to save weight...I bought one of the 26s from DDM and converted it that way...
Beats me why Zenoah makes all the different versions of a small engine, the one you have should run just like the G26 airplane version....

captinjohn

mikenlaplaz: Is that the way the cyl is ported as is, or did you do some port-work on it yourself? Thanks Capt,n

mikenlapaz

That is right out of the box. I did no port work.

Antique

My Feedback: (4)

Like I said above, why Zenoah makes so many different designs is a mystery...The transfers are the same size as the airplane G26, but because of the bolt pattern they could be modified wider than the G26...I ran a much modified G26 yesterday, ran the same as the stock one with the props we use for airplanes......Looks like Zenoah got it right the first time, unlike some of the others around here
That cylinder WILL fit on the G26 case with some widening and filling extra holes..No benefit except the cost, I think the complete bore up kit is less than the cost of a cylinder from the normal airplane engine supplier...Want to put the price and supplier on here , Mike ?
A converted scooter short block from DDM runs about like the airplane G26 if you want to do some trimming and buy a C&H ignition....
Yes, already tried the scooter short block with the full circle crank...Not worth it to me, costs about the same as the wholesale cost of a G26PUM by the time the cost of the extra parts and time are added in....

mikenlapaz

Ralph,
All of the parts are available on-line from Dave's Discount Motors. They appear service and customer oriented. They make it rather easy as they list the Zenoah part numbers. With a Zenoah parts manual it is just pick the items and fill your basket. Search: CA348, dd340, dd342 gets the main items.

One thing that puzzled me most of the day, the step-down stud for the prop attachment. I knew there must be a better way and it took some digging to find your new improved 2 piece prop hub posting in the gas section. Need someone to test on of those in a foreign land ! Do you stock and what is the price?

Zen flywheels are not configured be used as a backing for a prop hub. Toyed with reversing the crank install but that is not feasible. Got a mess to clean up on that idea.

mikenlapaz

It is easy to appreciate Ralph's skill. Had to magnify to see 2 parts and without the prop the securement is apparent.

arobatx

Hey Mike....thought those pics looked familiar

Antique

My Feedback: (4)

No problem reversing the crank, you can use either end...The stock G26 has a short front end tapped for the 6mm stud, the other end has the threads for the flywheel...I make the G62 lite 2 piece hubs using the outer piece as the nut to hold the tapered piece on the crank...It's a 10mm thread and is strong enough, based on experience with early Quadra 100s, they use a 5/16 threaded end to do the same thing...Never had a 10 mm Zenoah crank end break...The G26 could be made the same way, but looks a little weaker...The short block I bought from DDM had a full circle crank in it...I made the hub on that one the same as my G62 lite hubs, the outer piece is the nut that holds the taper part on the crank and is threaded for a 5/16 prop bolt...Another way is the old spool hub from an early G23 and a 6mm grade 8 bolt threaded into the crank like the G23...You can turn the end of the spool smaller and put a 3/16 ring on it for the magnet to trigger the sensor...Turn the front of the case for a matching ring to hold the sensor..Makes a nice clean install...The magnet ring has a setscrew in it so it can be rotated to set the timing....Green Loctite on the taper of the crank ensures no slip
DDM 25.6 without the tapered hub.The case bolts go all the way through to the back plate and are threaded in and cut off flush...
My DDM 26 ran just about like a G26 airplane engine, weighed about the same...If I couldn't get the airplane G26s I would use the DDMs......This one was done in a hurry, wanted to see how it worked out..There could be some more trimming done on the cylinder and case, the cylinder is a little chunky and could be rounded off...

arobatx

Hey Ralph,

what's your take on the .005" cylinder gaskets? Thumbs up or not, assuming without porting along with it? This would be in reference to the G62 and G26...

Also have you played any more with rounding off the cylinder fins on either engine? Just curious how that came out...

Antique

My Feedback: (4)

Tried it, not much difference at the rpm we use...Probably works good on the scooter engines, they turn up a lot faster...
Rounding off the fins looks better, doesn't save enough weight to bother with....IMO

ryan@ddm

Ralph, can you provide further details on your results on the G62 with the .005 gasket? RPM differential, spool-up time, etc?

Changing the squish from .035 to .020 should make a noticable difference, and I'm surpised by your response...

arobatx

Hey Ralph, I figured that might be the case on the fins, regarding weight! You have a picture of a 26, 62 or both with the rounded fins you could throw on here?

Antique

My Feedback: (4)

G62 with .030 squish...Altitude 6800, air temp 52 degrees, 24-8 Menz S prop, 32-1 87 octane fuel, 6700 rpm..
Same engine 5 minutes later, .015 squish 6700 rpm...
The TNC tach was showing 6600-6800 both times....
I ran a customer's reworked G26 yesterday after conversion...Had a lightened piston and some port work, don't know about the compression but I suspect it was higher than stock...18-6 Mejzlik prop, no muffler, 9000 rpm...
Ran a brand new conversion, otherwise stock, 9200 rpm...It was an exceptional engine, most run about 8800-9000...I ran a good used one converted last week, 93-9400 rpm....
The stock muffler kinda sucks, 8200 rpm max......But it's quieter
A Slimline Pitts runs at least 400 rpm faster and sounds way better, no way to measure Dbs
Sorry, no pictures of rounded off fins...I went to almost the large mounting bolt holes in the cylinders...Look really good polished [8D]

ryan@ddm

This makes sense. Using the gasket has the effect of lowering the exhaust port .015". A lower exhaust port should lead to reduced top-end RPM's but improved torque. Here, the RPM's did not fall off at all, due to the improved power generated by the tighter squish.

The takeaway: a teensy bit of exhaust port modification (raise the roof back up to where it was, or slightly higher) in combination with this .005" gasket will likely result in a notable RPM gain without sacrificing power down low.

mikenlapaz

Some interesting reading on Zenoah prop hubs.
http://www.rcuniverse.com/forum/m_17...tm.htm#1789685
http://www.rcuniverse.com/forum/m_22...tm.htm#2260388

Ralph:
The rotor on G62 is tapped for hub bolts and is flat faced. I believe, the flywheel for G23-26 is not adaptable.

"The G26 could be made the same way, but looks a little weaker..." Yes, If you had the rotor. Without the rotor I'm looking for options. It seems that it may be a weight penalty, but if I had it, it would be a consideration.

I have 1.5" 6061 aluminum bar stock. I lack the tools and skill to do inside tapers. Inside shoulders will have to be drill bit tip tapers or JB Weld and Vaselined crank! Would any benefit be worth the effort?

The B H Hansen 2 part hub is an attractive option, as pictured

"Another way is the old spool hub from an early G23 and a 6mm grade 8 bolt threaded into the crank like the G23..." The 'old G23 spool hub, just how were they constructed internally?. I have never seen one and the good stuff is always on the inside! I can see the difference in a high grade bolt Grade 8 (10.9 metric) versus a stepped down stud.

Any idea if the 2 piece hubs are machined from a 2000 series aluminum?

Antique

My Feedback: (4)

I designed the hub, the tapered part is 6061, the prop part is 2024, the allens are 10-32 grade 8, the 6mm allen is metric grade 12.9, same as US grade 8..I put the hubs on with the top one a little loose, then use a dial indicator the get the top part EXACTLY concentric, the 3 allens are about .004 oversize to allow for sideways movement...Runout is less than .0005 at the top...

The old G23 hub just fits the taper and is necked down in the middle...It sticks out past the end of the crank..There was a 6mm threaded rod in the crank and used a nut and lock nut to hold the prop on..A long 6mm allen works very well with this setup...
The old G23 had the flyheel on the back with the threaded end of the crank for a nut to hold it on...I have a few of these old flywheels here, you could cut off the excess diameter and use one for a short prop hub...

av8tor1977

My Feedback: (6)

Beautiful work!!

AV8TOR

Antique

My Feedback: (4)

If you still lived in Ashfork you could have a hub in about 1/2 hour...Send me your address, I already cut down an old flywheel.....

mikenlapaz

I had quite a few problems trying to get just a good center section out of a Zen flywheel. The combination of cermaic magnet , layered steel all hidden to within 1/2" of the bore it was a mess. The old flywheel/rotor is it similar in shape to the new G26 & G62 rotors? Does it have existing threaded holes for attaching things to it?

Antique

My Feedback: (4)

The old flywheel is completely different, larger diameter and thinner in the center...there were two tapped holes in it, I cut it down past the holes to use a hub that screws on the crank threads with some Loctite...I put the hub on an engine and faced the top surface to make it exactly 90 degrees to the crank, no runout .....It's in the mail tomorrow...

mikenlapaz

RCIGN: Super! Thank you.

On to a different part of the project.

mikenlapaz

Rotating the carb for linkage alignment and maybe a weight savings. A stamp pad to ink the surfaces helps me during layout and making references for drilling and grinding openings to match carb and engine. The factory insulatorn/heat dam was small to both the carb and exhaust port. Material: 3/8"" G10 Garolite (McMasterCarr) The M5 x50mm were too long so I opted to shorten them to 44mm with a velocity stack.