Every couple of months someone comes calling looking for details about a mod a did a while back to the Duncan Speed Beetle. After reviewing my posts on other forums I realized that I had never published my mod here, and, since I brought it up in another thread here, I thought I’d add it to the YYE mod forum. So, without further ado, I present to you…
The Speedle 720
Why, you ask? When one gets a few Speed Beetles for $2.39 a piece, and one dislikes paying for the Duncan friction stickers that do not last long, one begins to play…
Here’s our target victim:
Taking inspiration from the YYF Loop 720, I present the Speedle 720 with string response:
Inside views:
…and the obligatory edge-on view:
So, how does one go about creating the Speedle 720? Disassemble the yoyo and drill a series of eight holes in each half. I used a #36 drill (0.106" diameter). If you only have fractional drills available, a 7/64" is a good one, at 0.109" diameter…close enough for yoyos! If you are so inclined to set up your vertical milling machine, the eight #36 holes are symmetrically located every 45 degrees on a circle of 0.6563" diameter. Where did that diameter come from? Simple. My o-ring mod used a 0.750" OD 3/32" thick o-ring, and the nominal diameter for machining the o-ring slot was 0.6563". So, when I went to do the 720 mod, I left my machine setup and replaced the mill with a drill! Simple.
I have .pdf file available with an actual size template of the hole pattern used for the mod. I can email that to any interested modders.
Here’s a nice shot of sewing (or lacing) a yo-yo!
And finally, the completed yoyo halves…
The initial string response (yellow string) is made from a #6 Highlights string, as is, untwisted, and uses a doubled pattern (2 rows of string). It takes a little less than 1/2 a string to do one side of the yoyo. This resulted in a rather thick response system, and I don’t recommend this at all.
On the green string version, I laced all six threads from an untwisted #6 Highlight at once, as the above pictures show. I was not able to completely remove the twists using this method, so the next time I lace one I may use three threads at a time and go around twice to get a response made from six threads. This way I hope to keep the threads tighter, parallel, and flatter.
Due to the molded structure inside the the yoyo half, the string response needs to go over some of the plastic walls while threading, but, as the walls are symmetric across the diameter, this does not cause any balance problems. I still need to take a photo of the inside of the yoyo after the string response has been threaded.
How does it play? Smooth. The untwisted green version play smoother than the first (yellow string) version. Also, since the response surface is thinner, I can use the narrow, silver bearing spacers on the green version. The yellow string version response surface is so thick that the wide, brass colored spacers are required. I definitely prefer the untwisted Highlight version of the response system and only use that method now.
For the main string I have used both cotton and 100% polyester strings, and they both perform just fine. I have not yet tried 50/50 strings with the Speedle 720.
After “fixing” the response system of the Speed Beetle, my only remaining complaint is that it needs a little more weight. Ideally, additional weight for a looper should be concentrated near the axis of rotation, not the rim, so as to permit the yoyo to flip over while looping. Once I devise a simple solution to this problem I will let you all know.
Now, what about the Duncan Pulse, which is essentially a Speed Beetle with some internal electronics and LEDs? From what I can tell, the electronics appear to get in the way of the response lacing, but I’m not certain. I picked up a couple of Pulses to explore this, but have not yet taken them apart.
Who says cheap yoyos can’t be fun? 
db