My Sidewheeler
  Steamboats,Model Engines and More!  
-  My Profile


-  My Sidewheeler




-  Hand Pump

-  My Trailer

-  my engines

-  Steam Engines

-  Elec Motors & Engines


-  About steam paddleboats

-  PM Dynamo

-  No.8 Marine Engine by P.M.

-  PM's Boiler #1

-  Guestbook

-  Game Battleships


-  Game Cannon

-  Building the boat hull 1


How I built the




 PM Research is a great model engineering company with many steam engines, model boilers, solar engines and much much more. I have completed 7 or 8 of their kits and found them to be of the highest quality. Their castings compare with Stuart, one of the oldest leading model engineering companies. Since the dyno is their latest release I thought I would do a build article on the way I approached the machining of the dyno. I am a self-taught "rank beginner" when it comes to machining. All it takes is the will to want to build your "project" and a little guts to try it. This kit is a real beginners kit and would make a great first project on your new lathe. A mill is not necessary but makes life a little bit easier. Instead of milling the bottom of the castings one could use several methods such as a belt sander, grinding or even a hand file. I opted to use my combo mill-drill and lathe that my wife gave to me as a Christmas present 5 years ago. She didn't know the monster she was creating! The machine was purchased from  Grizzly Industrial and I've enjoyed it very much. A couple of minor problems that were solved by a few phone calls and installing a new start capacitor on the mill motor. The company has a great support team to help you.

I started by machining the bottom first. The casting was carefully set up in my mill vise with a couple of parallels under the mounting lugs. I wanted a little clearance under the two  end covers so I left it about .015 high. I checked the aluminum end castings and figured out just how much to machine off the bottom of the main casting. With that step done I checked to make sure the machined bottom was parallel with the top. There was about 5 thousands difference between the 2 ends. Close enough for me who was used to measuring to a 1/8 or so when I was working as a steamfitter. I then put it back in my mill vise with the jaws on the bottom and the other jaw on the top of the casting. I then just milled down to ensure the end was reasonably square with the bottom. With that done I now could start the lathe work.


Total time to read the instructions and do the milling operations:

1 Hour



 I dreaded the thoughts of changing to my 4 jaw 8" chuck as its heavy and bulky to use. I tried the casting into my 3 jaw chuck and found out if I machined the bottom as shown in the plans it would have chucked right in. Because I left on the .015 I put 2 shims of .015 each under the 2 jaws that weren't in contact with the bottom. I "seated" the casting on a piece of 1/8" aluminum scrap so when I bored it I would not cut into the face of my chuck. I then used a dial indicator to check to see if it was running true. I readjusted one of the shims and was pleased it was running within .005 or so. Good enough for me as the castings were off a little also.

I then proceeded to face off the one end to the right dimension. I then changed over to a boring bar and started to open up the core that was cast in. To my surprise the core was very accurately placed and was pretty much on center. I didn't measure it as has to be opened up quite a bit. I took my time only taking cuts of less than .010 each pass. I'm glad I placed the scrap against the face of the chuck as I could machine into it a bit without worry of hitting the chuck. After 20 passes or so I finally reached what was called for. I made the last few passes taking only a .001  or so to ensure my hole was straight and not bell-mouthed.


After the lathe work was done I laid out the four mounting holes and the eyebolt hole in the top center of the dyno.  I used a layout fluid on the bottom and a scribe to mark the holes. After carefully checking my layout I center punched the 5 holes. I again used my 3 in 1 machine to drill the holes. I used a centering devise to locate the mill head directly over each mark. The picture shows me centering over the 3rd hole in the base.



I then removed my centering devise and drilled the hole through the casting. Notice I slide the parallel over to clear the hole






 The top center hole was then drilled. I could have done these steps before the lathe work but I was anxious to get to the lathe work.




One of the last machining steps on the base would be to face off the rough casting where the mounting screws would hold it down. I cleaned up the mold marks and high spots with a hand file. The sharp edges left from milling were slightly rounded except for the inside edge of where the face meets the large bored hole. I wanted this to be fairly square as the end bells fit into the bore by only 1/32 of an inch. The base will still need 8 more holes drilled and tapped to hold the ends in place. I decided to machine them first and then locate the holes. The hole locations are given on the drawings but if an error were made on the end plates the tapped holes would be useless. I wanted each of the bolts to be centered in the raised boss for cosmetic reasons only. I will soon find out how accurate PM's castings are.

Time for these steps

1-1/2 hours

Total now @ 2-1/2 hrs.

I set aside the main casting and started to setup for machining the two end caps for the dyno. They are a little different as one of them also doubles as the brush holders. It was a simple matter of chucking them directly into a 4"-4 jaw chuck on my 7X12 mini lathe. I used a couple of pieces of brass shim stock as the jaws on the chuck were very close to the end of the four raised bosses where the mounting holes were to be drilled. I checked both the inside opening and the outside of the casting to make sure it was centered correctly. The castings were running pretty true with only a few thousands difference between the inside and outside. Pretty good for an aluminum casting. I came up with a happy medium between the two and faced off the casting as a first step. The plans call for machining off 1/32". When I got down close to the right diameter to fit into the main castings bore I took cuts of .001 until I had a nice snug fit into the main casting. While it was still chucked into the lathe I center drilled the hole for the bushings to be installed in the end. I used a 15/64th bit for the hole and followed up with a 1/4 reamer. If I had this step to do again I would have used a smaller reamer such as . 2495 as the bushings were a little on the sloppy side. No big problem as a little high strength locktite will hold them in place. All that's left to do is to drill the holes that will hold them on. I then remembered that a friend borrowed my 4" rotary table I was anxious to finish my project so I laid out the 8 mounting holes on the raised bosses. I also did the 2 for the brush holders to mount to. I do not care for the screws furnished by PM. Although good quality I wanted a hex head instead of a plain slotted screw. I wish that PM would furnish hex head but I can understand that would raise the cost up a little. I checked my supply of small hex head and only had 2-56 & 4-40. I decided to use the 2-56 instead of what was called for. The method's I use to locate the holes in the main casting are a bit unusual. Because I used my eye to locate the holes in the center of the bosses I only drilled them out to the same size as my tap drill. (#51 for 2-56). The reason I do this is I can locate them in the main casting more accurately this way.  I drilled all 8 holes with a # 51 drill.  I then drilled the two 1/8" holes for the brush insulators as called for. I then give the end cap and the main casting a coat of contact cement and allow it to tack up a little. I simply glue the end into place. The contact cement is still a little pliable so I can index it to the proper position. Note: I started to index the end cap in the wrong position; it should be turned 90 degrees. I now can index to the center of each hole and drill down into the main body casting. I placed a # 52 drill into the first hole I drilled just in case it tried to turn I wouldn't lose my indexing. I then finished off the remaining three holes and then did the other side the same way. I put a small mark near the bottom so I can easily put them back into the same place. Now with all the holes drilled I tapped the main body using a 2-56 tap. I didn't have a bottom tap so I drilled them to 3/8 deep instead of what was called for. That way I could tap them a little deeper. I left it in my mill and centered over each hole to make sure my tap was going in straight. I then redrilled the 8 holes in the end pieces for clearance for the 2-56 screws. I tried the ends on the main base casting and everything fit just fine. The first time I tried to do something like this I did it by measuring, prick punching the holes and then drilling them. It fit "LIKE SOCKS ON A CHICKEN".  


Time Spent 2-1/2 hrs.

Total to date  5 hrs.


Now that the base and ends are done all that's left is the eyebolt, spacer, two binding posts and the drive pulley. Before I did the machining to these parts I painted the two ends and base with Rustoleum texture dark green paint. I like it and paint most of my engines using this paint. It have a very fine sand like finish to it. Then I started with the eyebolt and spacer which is striaght forward. The pulley was done next cutting a slight bevel down from the center and finished it up with a file and fine emery cloth. A couple of friends who are steam engine collectors talked me into building a couple of more dynamos for them. I bought 2 kits so that would leave me 3 more to machine over the Winter. Since there are 2 binding posts for each dynamo  a total of 8 pieces would be needed. I decided to make a profile tool to turn them on my lathe. I used a piece of tool steel and ground the profile of the binding post into it. This is the first time I tried something like this. I gave it a little relief on the underside and gave it a try. I worked like a charm. I made all eight of them including the drilling and tapping in less than 1 hour. A job that I thought I would hate was real fun to do. It took me less than ten minutes to make the tool but saved much time in the long run. They came out slightly larger than what was called for but I'm happy with them. This completes all the machining to make the dynamo. Now for the best part!


The Assembly


 I started the assembly by following the excellent instructions given by PM Research. Shown in the picture is the magnets being held in place with a spring clip. The first step involved putting in the eyebolt and the aluminum spacer for the magnets. The armature was checked by installing both ends, but no brushes. Everything fit like a glove. I disassembled it and then followed PM's assembly manual to complete my dynamo. I then fastened the brushes to the brush end casting as shown on PM's Assembly drawings. I mounted the brush assembly to the main frame casting. The binding posts must be vertical or the unit will NOT work properly. The armature was the carefully inserted into the frame. You must be careful and lift the brushes. The shaft end cap was then screwed in place. All that's left to do is to install the drive pulley on the end of the shaft. Knowing a little about motors I decided to "break it in" by running it with 7.2 volt nicad pack from one of my model boats. I made sure I ran it the same direction as I planned to use it. That way the brushes would be worn in the direction that it would be used for generaton. It probably doesn't make much difference but it sure makes me feel like I'm getting the most out of it having broken it in first.


PM did a great job on their Dynamo Kit. The price is right at only $45.00. Thanks PM

Time for these steps 3- 1/2 hrs

Total Time 8-1/2 hours

Included were 6 additional binding posts








   A beautiful job by Carl Swanstrom

Visit his web at

Carl's Collectables

- Web Poll on Dynamo



© 2006 All Rights Reserved.