10/28/02 - Electric Start for the ICE (first on-board, then off-board):

One of the things that worried me the most about using a gas engine, is that it might stall after a good weapon impact. I probably put a little too much stock in what a lot of people say on the various builders internet communities I frequent. I have read many posts from builders (MOST of which don't even HAVE a robot with an ICE, or a robot at ALL for that matter :) ) saying how grave a mistake it is to NOT have an on-board electric start for any ICE in a robot. It actually worried me enough that I started trying to come up with a simple remote start.

One of the difficulties in designing an electric start, is that once you start the engine you want the drive that you used to turn the motor over, to disengage. After toiling at this problem for a while, I decided to take advantage of the mechanism that Husqvarna had already designed to do this: The pull cord assembly! When you give the pull cord a yank on a small engine, a spring makes the cord coil back up. When the engine starts, the plates that the pull cord assembly are touching are disengaged when centrifugal force makes the points of contact "fling" out. So, by removing the cord, and the coiled spring that made the cord wind back up after a pull, I could attach a sprocket to the mechanism and drive it with an electric motor, instead of the cord. Did that make any sense at all? Probably not... That's why I take lots and lots of pictures :)


My fears of the engine dieing were laid to rest a little, after watching Adam Baxter of Team LOGICOM fight @ the SECR "Southern Assault 2002".

Adam's awesome robots CHOPPER and Code:BLACK both have STRONG 2-stroke engines, and neither suffered the loss of a weapon in any fight at the event, due to the engine dieing. Neither bot has an on-board electric start, either. Adam actually told me that in all the fights he has fought with BOTH bots, he has only stalled once. He also shared a lot of info on just how difficult it is to MAKE an on-board starter for a small 2-stroke without spending a lot of your weight budget. People underestimate the torque required to get a small 2-stroke up to the speed it needs to turn, in order to start. After trying to start the engine with my cordless drill, I found out that it doesn't even turn enough RPM's to make the spark plug arc! It actually takes OVER 2,000 RPM's to get the plug to spark on a chainsaw type 2-stroke, and then it takes a LOT of torque to keep the engine turning until it starts.

SO, after learning a lot from Adam, and from trying different things to start the engine I decided against the on-board starter, and made my own off-board starter: FRANKENSTARTER! I spent so much time on the on-board deal though, that I still wanted to post the pics. :) So you will notice that the first half of this report will focus on the "on-board" starter that I will not use, and the second half is about the "off-board" starter "FRANKENSTARTER" that I made to fire up the Husky before fights. My starter was inspired by the cool go-kart starter than Adam uses on his robots.

Note: You will see that the portion of the report that focuses on the "on-board" starter, reads like it was what I was going to use. This is because I actually wrote the "on-board" part with pics, before deciding against using an on-board starter.

Click Thumbnail For Bigger Pic:

1) This is the 28 tooth nylon sprocket that will attach to the back of the part the pull cord used to be wound around.

2) The part the pull cord used to be wrapped around. I'll just call it the pull cord thingy from now on (or PCT for short ;)

3) In the very first pic, I was lining the sprocket up to drill THIS hole. I had to increase the bore of the sprocket to 1/2" to fit over the "axle" the PCT spins on.

4) Yay, it fits! Of course, a LOT of hacking will have to be done to: Make the sprocket fit in the space behind the PCT, Attach the sprocket to the PCT, and Make a hole in the plastic molding for the chain to transfer power from the electric motor, to the sprocket attached to the PCT.

5) Need to remove some plastic from the PCT, to help make the sprocket fit in the cramped space behind the PCT. So I put it in the vise...

6) ... and got my remove on!

7) Much better.

8) The collar had to come off the sprocket too.

9) So I took it off!

10) Well, most of it anyway... I ended up removing ALL of the collar eventually though, after a LOT of trial and error to get everything to fit.

11) The molding piece that has the axle the PCT and sprocket ride on, must be modified to allow chain to attach to the sprocket. So next I get to butcher some plastic...

12) I have found that a Dremel and abrasive disc's melt through thin plastics nicely.

13) Just getting started...

14) I wonder if these types of mods void the warranty?

15) The Dremel doesn't like the thicker plastic though, and starts to goo up.

16) Starting to look promising, but I still have a LOT of hacking/grinding/filing to make everything fit properly and leave room for the chain.

17) The PCT had to have some more material removed, to make room for the chain to run on the attached sprocket.

18) I used the dremel to remove one of the "walls" that had originally kept the pull cord spooled up. Then I used a file to clean up the rough edges.

19) Looking a little better, but I still had a LOT of trial and error and filing to get the PCT whittled down to the right size. I spent an equal amount of time on the sprocket collar too, which was eventually reduced to NO collar.

20) You can see where the chain will go through the plastic housing, to attach to the sprocket here.

21) Loosely thrown together to show the method of power transmission to the Pull Cord Thingy (PTC).

22) After FINALLY filing the right amount of material off the PCT to make the sprocket fit properly, I drilled four holes through the PCT and sprocket to guide plastic screws through, and attach the two pieces.

23) Attached! The fourth, offset hole on the left was to get around a feature on the front of the PCT.

24) You can see the feature I was referring to in the previous pic, on the right in this image. It was the hole that the original pull string went through on the PCT.

25) Here is the start of an aluminum bushing I made to go under the sprocket that is attached to the PCT.

26) I cut a square out of the AL around the 1/2" hole I drilled.

27) Then removed the corners, and used the file to make the 1/8" thick AL bushing roughly "round".

28) Putting it together, here you see the new bushing in place and the sprocket/PCT assembly going on.

29) Finally, the retaining screw goes into the end of the axle, to hold everything in place.

30) The newly modified assembly bolts down to it's original home, only a sprocket drives the PCT instead of a cord now.

31) After mucho filing and cutting, it finally looks like it will work!

32) Sure, I need to clean up the plastic hackings :) The chain DOES fit onto the sprocket though, and theoretically could have been driven by an electric motor... BUT this was as far as I got with the on-board starter.

33) This 3/4" steel tubing is the un-cut body of what will become: FRANKENSTARTER

34) Down with the lever of the Makita CHOP SAW, to form the vertebra of Frankie's spine.

35) Making some holes in a piece of the tubing, for the DUAL EV's to mount to.

36) These pieces of steel will support the pillow block bearings for Frankie's SHAFT. He's gonna be one bad Mutha... SHUT YO MOUTH!

37) I wanted to make the starter completely out of items I already had on-hand. So I used EV's, bearings, and sprockets that had once been used in Village Idiot.

38) I also used the two extra motor mounts that Kenneth made for me. (thanks Kenneth!!)

39) Everyone knows, you have to push some electricity through any sci-fi monster to bring it to life. Team RV brings all the monsters it creates to life with the "MonsterMATIC-135" created by the good folks @ Hobart.

40) Clamping another one of Frank's "Limbs", before gluing it on permanently. Sewing on limbs is for a seamstress, I prefer the "melt-n-cool" method of limb attachment.

41) More welding.

42) One of the pillow block mounts attached.

43) Last piece to melt into place before I can get my grind on.

44) Ready to smooth out some rough spots.

45) Throwing the parts into place to get a rough idea what Frank's bod will look like.

46) Sparky! Sparky!

47) Frankie needed a button to get the motors running, so I hacked up an extra Hella-Switch I had to act as a "push for on" button to run the starter.

48) I used a 3/4" non-keyed shaft for the starter shaft.

49) I don't know what I would do without my lovely assistant, and part-time pic taker Angie!

50) I needed a way to keep the shaft aligned properly with the flywheel while spinning, so I drilled the end out of the shaft to slide over the nut that holds the flywheel on. The hole was off-center, but it is pretty hard to drill a hole in the top of a 3' long shaft using a drill press!

51) So I used a file and a Dremel to make the hole more straight, and big enough to fit over the head of the nut that holds the flywheel on.

52) The finished hole in the end of the shaft.

53) Will it fit?

54) Yep.

55) I welded a sprocket on the end of the shaft, that catches the teeth that fling out on the fly wheel (see "teeth" in pic #53)

56) I attached the wires and hooked up the Hella-Switch just to try the starter out.

57) It worked! But it is ugly :) Here is the start of the "clean up" process.

58) Here's a shot right before I started cleaning up the wire mess, just to show the scale of the starter.

59) After figuring out how I wanted to run the wiring, I stripped the starter down to the frame and painted it red.

60) Dry and ready to have some goodies re-attached.

61) I used some "cold-shrink" to put over the handles, for a cushy grip.

62) Frank try's on his dressed up 2HP of ICE starting MUSCLE!

63) Tap the button on this sucker and it feels like it wants to jump out of your hands :) I will probably use it as is, with the exception of possibly adding a chain guard in the future.

64) All dressed up, and ready to start engines! I also made an extension cord, that plugs into the base of old Frank to juice him up with any 24V power source. I currently use two 12v SLA batteries in series for FRANKenJUICE.

rv forum | team members | rv chat | build diary | trip reports | video archive | sponsors | team RV bots

2001 RV. All rights reserved.