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Drum Brake Failure at Speed....Ouch. Something to look out for? Thoughts/Comments?

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Anyone ever see this happen before? Happened to me Friday night at about 50mph. Locked the front end up, went down, slid about 30 foot, t-shirt and shorts (yes, I SHOULD HAVE learned my lesson from Heather's fall at LJ!). I'm fine, but some good road rash. Bike is fine, but put a few more dings in it. Always wear your gear! Even for a quick little ride! Thankfully it was very close to my house and there were no cars around. Could have been MUCH worse with traffic involved!

First thing- I suppose it could be something to look for? Maybe save someone else some pain?

Second- Any thoughts on preventing another one in the future? I have a lot of bikes and friends all on drum type front hubs. I know 2 of our bikes have noticeably sloppy fits between the link locating pin and hub recess. I don't remember how this one fit. I had rebuilt the hub several weeks ago (it was definitely the strengthened type), cleaned up and adjusted everything real well and actually had good brakes! I've thought about one of the numerous outboard disc brakes, but they're expensive and some use the drum link style. I'm thinking convert to inboard style disc, which uses a locating stud instead of just a pin? Think that would be safer?

 

Or assume it was a rare failure and just rebuild as drum style and carry on? 

 

IMG_1362.JPG

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Wow. I've seen this happen on early back plates but not a later type. 

That looks pretty bad. 

Did it happen as you applied the brakes?

I'm glad you are not too hurt. That could have been a total

disater in traffic. 

 

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I got nothing, but just wanted to say, really glad your ok. A mutual friend of ours had his front tire blow out. No helmet. He had head trama and had to learn a few things over again. Even years later his memory still isn't quite right. 

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39 minutes ago, theageofindustry said:

Damn! Was that the early type with the smaller gusset?

 

Glad you are ok, don't do that again!

I'd really like to not do that again! As Corey asked too, it was the strengthened type. Later ser 3 version. It was on my ser 1, but I swapped the weak type out right away! That's what kinda bothers me. I can't find a reason for it happening, and therefore can take no steps to prevent it happening again. That's why I'm thinking maybe a disc set up is safer?

 

1 hour ago, Lambrettayeroc said:

 

Did it happen as you applied the brakes?

 

It did. Granted, I was applying the brakes pretty hard, and they were working very well, so there had to be quite a bit of pressure on it. But I still wouldn't think that a strengthened type would just crack like that. It wasn't a reverse pull or any other type of deviation from a standard set up, so you'd think I was well within the design limits.

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I think the little locating stub from the link was slopping around in there and it bit at an angle inside that track, causing all the pressure to be in a very specific spot. So it cracked and the hub spun around. I have seen this on hubs that are loose. A way to test is to roll your scooter forward and apply front brake while turning the wheel to the right. If the top of the tire twists away to the left, then something is not right.

Isn't there a shop somewhere that had a bushing to fit over the locating stub on the link to take of slop?

 

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Damn the MON crew needs to be on their guard for the next few months until this run of bad luck passes. Really glad you are ok... We've talked about your forks or frame being bent on the S1, do you think that the load vector applied to the backing plate during braking has changed and therefore loaded a weaker section of the backing plate, causing failure?

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If the lug was wallowed, as UJ said, the constant slapping backwards and forwards could have caused some fatigue. Could have also been a bad casting on the hub or a poor alloy mix used that day.

 

Most important part is you and the bike are ok.

As far as wallowed out lug, in the days before a tig set up was here at the shop so the lug cold be welded and machined to the correct size, a piece of aluminum shim set up in a horseshoe shape and pushed into the lug stopped all slop just fine.;)

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3 hours ago, upjettr said:

I think the little locating stub from the link was slopping around in there and it bit at an angle inside that track, causing all the pressure to be in a very specific spot. So it cracked and the hub spun around. I have seen this on hubs that are loose. A way to test is to roll your scooter forward and apply front brake while turning the wheel to the right. If the top of the tire twists away to the left, then something is not right.

Isn't there a shop somewhere that had a bushing to fit over the locating stub on the link to take of slop?

 

It could very well have been loose in there. I was just talking with a friend that has that problem about making link pin bushings. That may just have jumped up my "list of things to do" about 15 spots. I've got the equipment to make them. Time to go through all the bikes and start measuring stuff!

 

1 hour ago, Aaron Hecker said:

Damn the MON crew needs to be on their guard for the next few months until this run of bad luck passes. Really glad you are ok... We've talked about your forks or frame being bent on the S1, do you think that the load vector applied to the backing plate during braking has changed and therefore loaded a weaker section of the backing plate, causing failure?

I wouldn't necessarily remove that idea from the list, but I forgot to tell you at LJ, I pulled my frame out the week after PVSC! It was crunched in about 2 1/4". I've also replaced the forks, fork links and bushings, front hub backing plate and drum, etc. All done to what I felt was acceptable condition parts and within clearances and wear limits. Everything was working and handling much better! I would be happy to accept making a mistake or installed a bad part, if I could figure out what it was!

 

Maybe it is a loose locating pin fit? I can take some measurements of the bikes I have and maybe with some help we could come up with a rough set of "tolerance limits"  for safety's sake? Only if people want to of course. But I'd hate to be aware of hazardous potential and not tell other riders about it...because that really sucked.

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Geez Adam I'm glad your ok.  I had a tire blow out years ago at 35 MPH cant imagine how bad it could have been if I was going faster.

Keep us posted on what you find out regarding tolerances and  if we need to take any measurements from our scoots for you to compare them to.

Pete

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I'm really sorry to hear this happened, Adam.  But glad you are OK!

I've been wanting to ask about this topic for about a year.  Both Li's in my stable have stock front drums.  Both have slop around the locating pin.  I've been worried that the pin "slapping" against the U would maybe cause fatigue.  But, I've never had a Lammy that didn't have slop around the locating pin, so maybe its OK or within spec?  I doubt it.

This topic is not addressed in the Stickies manual.

If you are to try making bushings, I can get you some measurements on the slop of my drums.  I'd easily buy two from you.

Mike

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I have seen it happen on the weak series 1 hub plates as well as a series 3 one.  I have had Jon @ Jet200 weld up a bunch of weak hub plates in the past.  

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Adam's story and picture made an impression on me back in July.  Since I had some slop in my drum, prior to reinstalling the links (after having Eric @ 2nd ave weld some damper mounts on), I went to HD and walked their hardware aisle looking for a solution.  It isn't what I had envisioned... but my solution was cheap and, so far, effective...

It may not last as long as a brass or composite bushing... but at ¢.79 for two, I've got a spare on hand.

 

 

Link Stud.JPG

Rubber.JPG

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Dam, I know about this problem, and fixed it on all of my Lambretta’s. This can happen to the J and LD also.
I’m taking apart a front hub right now to show you how I fixed the problem. I’ll have it posted later to day!
I’m glad you’re okay dude.

PS: That plastic piece will stop the clicking noise for a while, until the metal cuts through. The problem is that part of the hub should not be moving.

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Oversized brass bushing on the arms is probably the best solution if there's that much play.

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I have never seen this before- Maybe if it had slop and you hit a bump and the locating stub in the fork link jumped out or moved away from the hub and when it came back in to the hub backing plate  it was way outta line and just broke to bits under load and breaks on? Like how cast parts break before case harden parts will?

Glad your ok man.

I guess everyone should check their rides over. Good PSA

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This happened to me. Luckily, I had just got into 1st gear and wasn't going too fast. Weak hub as Mike pointed out. 

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Seems that reinforcing the aluminum in addition to taking out the slop is in order...

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How's the yellow screw protector holding up? Seems like a little peace of mind until something better is developed... ?

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Okay guys, its easy to fix, but hard for me to explain.
It only takes a washer to fix the front hub Back Plate moving, that could cause a brake on the plate side.
Here’s the correct setup for the hub and the problem.
tool_hub-fix1.jpg

tool_hub-fix2.jpg

tool_hub-fix3.jpg

tool_hub-fix4.jpg

tool_hub-fix5.jpg

tool_hub-fix6666.jpg

tool_hub-fix7.jpg

tool_hub-fix8.jpg

A lot of guys leave the Back Plate loose, so the tire will spin freely.
You should always have the nuts tight on the Back Plate and hub side before you put it on. If the nuts are tight like photo 5, and your tire barely moves. Your Back Plate or the spacers are worn down. Most of the time a small washer will fix the problem, then you can tighten down the main inter fork nuts on photo 5.

With the hub Back Plate loose, making the loud knocking sound. I was thinking, it could cause metal fatigue later and tracked down the problem and fixed it. That clicking / knocking sound drove me crazy. I had to fix it.

 

 

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The taken apart hub pictures are from my Series 2 with the worn down
Back Plate. The last three pictures are of my Series 3 Serveta. I was
showing how to test for the problem. My Jet200 had that shot spacer. It took me forever to figure that out. Thanks.

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10 hours ago, Tinman said:

How's the yellow screw protector holding up? Seems like a little piece of mind until something better is developed... ?

It's still early days... but it's held up just fine - no issues.  The rubber is pretty tough* and, in this use, I don't expect that it will fail quickly.  Heck, it's easy enough to check for wear.  It fit snugly into the plate bracket (but did not have to be forced) and removed all of the slop.  It's not the bushing I was looking for... but it was a cheap, quick fix.  The other possible benefit to this rubber cap is that it seems to be a pretty universal fit (conforming itself to the slight elongations caused by the link pin wear in the plate housing).  I wonder if a brass/aluminum/etc bushing will fit universally, given possible variations in "slop" from bike to bike.

Oh well, time will tell.  As you said, now I have a little peace of mind...

*During my bike rebuild, I actually used a similar cap on the brake pedal leg/stop (the bit that hits against the frame strut).  It's also held up fine (although I'm expecting this one to fail).

IMG_3224.JPG

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Why not adjust your brake cable correctly? Takes about 5 min and costs $0

 

Also your brake light switch looks like it's about to be in the "ON" position with the added bushing.

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