My main interest is Vintage stunt and here in Australia we receive a sliding scale of bonus points for the age of design and the age of motor, the older the more points. You get extra points for ignition, biplanes and or flapless designs.
I'm a better builder than flyer and enjoy searching for oddball suitable designs and the challenge of getting the less popular motors to run better than they did in their own time.
I have always thought that the "Pacemaker 59" was a motor that should be well suited to trying to make it work as a decent engine for OTS. Its features include a one piece magnesium alloy case, twin ball races, socket head cap screws all round, rear rotary disc intake and a listed weight of only 12 ounces for the ignition version, well according to the add on the back page of the Oct. 1946 Air Trails. It all looks good! then again you can't always believe the adds can you! Just checked the weight of my much hacked away job and find it weights in a just over 13 ounces and it hasn't even got a timer! The ignition version actually comes in at 14.75 ounces.
I'd bought a parts motor on ebay a couple of years ago more to check out than seriously use, the case and head had been filed, lugs broken out, shaft badly bodged at the drive washer and required a bit of TLC.
A good friend organised the repair of the broken lugs some time ago. I have now completed the engine to the first phase.
I figured that the lapped motor would benefit from an improved piston cylinder fit and the addition of some taper to the bore. The original motor has a parallel bore and a piston that has an undercut some .400" wide in the centre to reduce friction I presume. This allows the transfer port to breath through this annular gap into the exhaust on the down stroke and must compromise the basic crankcase compression. Having lapped some 0.003 taper into the bore I made a new piston from mehanite without this central relief. I discarded the bronze "H" section rod and searched my stock of rods for a suitable replacement found that an OS 80 rod has the same centers between the wrist pin and big end, all I had to do was rebush the rod at the big end. While the wrist pin in the OS 80 is huge at 7.30 mm o.d. it is at least hollow so I used the OS wrist pin too, just shortened the length and made some Teflon end pads.
The shaft had been badly butchered at the “D” drive area, an attempt had been made to convert it to a square drive with a file to suit an O&R style prop driver with poor results.
I ground the shaft down to just under the shaft thread diameter and made a split bush to accept an OS 60 prop drive which is even the same diameter as the front housing and looks like it was designed for it.
For the first runs I set it up in the front end of a Super Duper Zilch I had been given. I had to cut the venturi back some 9 mm to be able to get it far enough back against the firewall. The venturi i.d. was 0.290” so I was hopeful that it would work okay
The first runs in the back yard were kept short but were very promising on a 13X6 Zinger that had been cut back to 12.25 diameter I found in my prop inventory. I took it to the field were I ran it up with a couple of friends. To say it vibrated is an understatement. None of us thought the airframe would survive. The prop was perfectly balanced and I suspected that the rear rotor was the culprit. I’d seen this type of vibration before with some rear disc pylon motors from my former R/C days. I statically balanced the rotor and then had to wait for the following weekend to see if there was any improvement. The vibration was gone.
I’d made fresh lines 0.0015” at 64 feet and was now ready to fly, I’d taken my stopwatch and Tacho to see where we were at, but once I’d got the motor started, it sounded so sweet I forgot all about the tacho and stopwatch and just flew it. I could see a lovely white exhaust trail, but it was a fast rich 2 stroke run
To say it had line tension is an understatement, I had a smile a mile wide when I landed it.
I think the motor is way too strong for the model, but it’s sure great fun. I’ve just taken a couple of shots to add to the post. Hope they come out.
Has anyone else had seen any of these motors used or had any experience running the Pacemaker 59’s. Anyone use one at your recent VSC?
Cheers for now
John
I'm a better builder than flyer and enjoy searching for oddball suitable designs and the challenge of getting the less popular motors to run better than they did in their own time.
I have always thought that the "Pacemaker 59" was a motor that should be well suited to trying to make it work as a decent engine for OTS. Its features include a one piece magnesium alloy case, twin ball races, socket head cap screws all round, rear rotary disc intake and a listed weight of only 12 ounces for the ignition version, well according to the add on the back page of the Oct. 1946 Air Trails. It all looks good! then again you can't always believe the adds can you! Just checked the weight of my much hacked away job and find it weights in a just over 13 ounces and it hasn't even got a timer! The ignition version actually comes in at 14.75 ounces.
I'd bought a parts motor on ebay a couple of years ago more to check out than seriously use, the case and head had been filed, lugs broken out, shaft badly bodged at the drive washer and required a bit of TLC.
A good friend organised the repair of the broken lugs some time ago. I have now completed the engine to the first phase.
I figured that the lapped motor would benefit from an improved piston cylinder fit and the addition of some taper to the bore. The original motor has a parallel bore and a piston that has an undercut some .400" wide in the centre to reduce friction I presume. This allows the transfer port to breath through this annular gap into the exhaust on the down stroke and must compromise the basic crankcase compression. Having lapped some 0.003 taper into the bore I made a new piston from mehanite without this central relief. I discarded the bronze "H" section rod and searched my stock of rods for a suitable replacement found that an OS 80 rod has the same centers between the wrist pin and big end, all I had to do was rebush the rod at the big end. While the wrist pin in the OS 80 is huge at 7.30 mm o.d. it is at least hollow so I used the OS wrist pin too, just shortened the length and made some Teflon end pads.
The shaft had been badly butchered at the “D” drive area, an attempt had been made to convert it to a square drive with a file to suit an O&R style prop driver with poor results.
I ground the shaft down to just under the shaft thread diameter and made a split bush to accept an OS 60 prop drive which is even the same diameter as the front housing and looks like it was designed for it.
For the first runs I set it up in the front end of a Super Duper Zilch I had been given. I had to cut the venturi back some 9 mm to be able to get it far enough back against the firewall. The venturi i.d. was 0.290” so I was hopeful that it would work okay
The first runs in the back yard were kept short but were very promising on a 13X6 Zinger that had been cut back to 12.25 diameter I found in my prop inventory. I took it to the field were I ran it up with a couple of friends. To say it vibrated is an understatement. None of us thought the airframe would survive. The prop was perfectly balanced and I suspected that the rear rotor was the culprit. I’d seen this type of vibration before with some rear disc pylon motors from my former R/C days. I statically balanced the rotor and then had to wait for the following weekend to see if there was any improvement. The vibration was gone.
I’d made fresh lines 0.0015” at 64 feet and was now ready to fly, I’d taken my stopwatch and Tacho to see where we were at, but once I’d got the motor started, it sounded so sweet I forgot all about the tacho and stopwatch and just flew it. I could see a lovely white exhaust trail, but it was a fast rich 2 stroke run
To say it had line tension is an understatement, I had a smile a mile wide when I landed it.
I think the motor is way too strong for the model, but it’s sure great fun. I’ve just taken a couple of shots to add to the post. Hope they come out.
Has anyone else had seen any of these motors used or had any experience running the Pacemaker 59’s. Anyone use one at your recent VSC?
Cheers for now
John