Sheared Flywheel Keys, ADC, & Electric Starting- a few long thoughts

[Mehusieni]

Juice- I doubt that lugging your 510 caused your catastrophic failure. Might've been an oil pressure failure or a defective bearing but I doubt you did that damage from lugging the engine. Those big blocks are solid motors... plus they have a pinion gear starting system, I believe.

the electric starter system on the xlites uses a worm drive. The worm can not be driven by the ring gear, it can only drive the ring gear. When lugging a bike, the chances of the engine stalling are greatly increase. A stalled engine goes backwards for a very short period- sometimes causing damage to xlite motors when the ring gear tries to drive the worm.

I must've misunderstood the part about the xlite engines. A professional took the engine apart and oil systems was intact so must've been a weak bearing. Either way the rebuild is moving forward, only a matter of time before the new parts arrive

 

[Buster714]

I have my '11 310 in the shop for what sounds like the issue described in this thread. I thought the starter was going out so I've continued to start the bike using the kick in conjunction with the e start. On the last ride I started to experience lugging, as if starving for fuel, until the bike just wouldn't run or start any more. I put the new fuel pump in and couldn't get it started so off to the shop it went. It sounds like the mechanic is on the right track, but there are some details shared here that I will definitely pass along. Thank you once again Cafe Husky!

 

[WWWRU]

• the biggie-> the starter system uses a worm drive.... and worms cannot be driven- they just drive (IOW- it ain't going backwards. I've used this example before- think of a vise: you can't spin the handle by pressing the jaws closed).

I am in the middle of putting my e-start back together and decided to test this theory. Looks like the worm gear can be driven in either direction by the starter gear. This was just the worm gear though, maybe when the starter is connected, which adds mechanical resistance, things will be different.

 

[WWWRU]

Here is Howstuffworks text:
Many worm gears have an interesting property that no other gear set has: the worm can easily turn the gear, but the gear cannot turn the worm. This is because the angle on the worm is so shallow that when the gear tries to spin it, the friction between the gear and the worm holds the worm in place.

https://science.howstuffworks.com/transport/engines-equipment/gear5.htm

So I decided to geek out on this and dusted off my Machine Elements Design textbook, which has a whole chapter on worm drives!! Worm drives in fact do have a self-locking property which is produced by the friction force between worm threads and wormgear teeth. This friction force is highly dependent on the on the lead angle (or how shallow the angle of threads is). My text book recommends to keep the lead angle no greater than 5 degrees if self-locking is required. I found several pictures on the internet and did a rough measurement on the TE310 worm and it looks like the lead angle is roughly 15 degrees, therefore it is possible for the worm to be driven (as seen in the video above).

However, 15 degrees is still a fairly shallow lead angle (45, or even 30 degrees would have been better). Minor discrepancies in the fabrication tolerance or assembly alignment can further reduce this angle and therefore increase the friction force which will add to the self-locking property.

I do believe that the recommended repair procedure (increased flywheel nut torque and loctite, along with making sure that there is no excessive play in the worm/starter gear) is a descent solution, since effectively it increases the force the flywheel can apply to the worm before snapping the woodruff key. Also, keeping the starter motor clean will help to reduce the force needed to turn the worm. However, too much force from the flywheel can result in the entire worm assembly being pushed out the engine case, as some owners have experienced.

 

[Trenchcoat85]

So I decided to geek out on this and dusted off my Machine Elements Design textbook, which has a whole chapter on worm drives!! Worm drives in fact do have a self-locking property which is produced by the friction force between worm threads and wormgear teeth. This friction force is highly dependent on the on the lead angle (or how shallow the angle of threads is). My text book recommends to keep the lead angle no greater than 5 degrees if self-locking is required. I found several pictures on the internet and did a rough measurement on the TE310 worm and it looks like the lead angle is roughly 15 degrees, therefore it is possible for the worm to be driven (as seen in the video above).

However, 15 degrees is still a fairly shallow lead angle (45, or even 30 degrees would have been better). Minor discrepancies in the fabrication tolerance or assembly alignment can further reduce this angle and therefore increase the friction force which will add to the self-locking property.

I do believe that the recommended repair procedure (increased flywheel nut torque and loctite, along with making sure that there is no excessive play in the worm/starter gear) is a descent solution, since effectively it increases the force the flywheel can apply to the worm before snapping the woodruff key. Also, keeping the starter motor clean will help to reduce the force needed to turn the worm. However, too much force from the flywheel can result in the entire worm assembly being pushed out the engine case, as some owners have experienced.

actually, there is another thread where my pet-theory was disproven. In fact, there is a video of the flywheel/ring gear turning/driving the worm just fine. The dished out section of the ring allows this, I'm thinking. However, if there are any imperfections on the ring (especially) resistance goes up sharply. It really has to be nearly perfect surfaces.

I also still recommend not doing this too much or too often (ie, dumping the clutch when rolling backwards).

the cafe husky user who edjumacted me is named Seth Mitchell (hi Seth) but I can't remember his user name. I've been really, really, REALLY meaning to update my theory but, unfortunately, I've been diagnosed with pancreatic cancer- and shit has been falling apart for the last 3 months.

I guess this is a small opportunity to set the record straight, so thank you. Unfortunately, I propagated this theory in a few threads; but I just don't have the energy to hunt 'em all down and correct the info. If someone could add at least a small note detailing the correct info when they stumble across a thread, I'd be grateful.

I've talked to many good people and made some good friends here at Cafe Husky. In fact, in my 37 years on the internet, this has been my favorite forum of all time. It's been fun and I learned a lot.

good luck.