Broken set screw......argh.

[StudEbiker]

So I am getting pretty close to having it all put together on my mid-drive unit. I got the shaft in and all the collar locks and gears in place and I was going to go back and loc-tite some set screws. I got the first one done on the #25 sprocket and went to do the second one ans as I was turning out the set screw only half of it came out. Argh! Not any hex head left on the piece still in the sprocket to get a bite on to turn it out. Of course the #25 is the hardest sprocket to get to because it's the only one in between the two plates. So what should I do here? Is it practical to try and get the old piece out? It is a very small screw and it is deep in the sprocket. Can I try and get it out with the drive still together or am I going to need to remove the sprocket? I would really like to avoid doing that if I could. Or should I just run it with one set-screw? The good news is, I think the broken set screw is tightened, there just isn't any loc-tite on it. Is it just me, or is there always a little thing like this that happens just as you think you've crossed the hump on a project?

close1.JPG (109.23 KiB) Viewed 1194 times

[AussieJester]

Is it just me, or is there always a little thing like this that happens just as you think you've crossed the hump on a project?

close1.JPG

DEFINITELY not just you buddy in fact, this EXACT same thing happened to me on the blue cruisers
output pulley when i was running the belt drive...sorry to have to tellz you i had to cut the
pully near in half to remove the area the set screw was in to get the bloody thing off, they
are bitches, set screws suck ass i have alot of them on both bikes and i get nervous
every time i have to try get one undone, i wont run them without loctite so its always a gamble getting the damn things off, i have a collection of small size allen keys with rounded ends from this lil set screws...

I wish you well getting it off, if its already in the correct place and doesnt really ned tobe removed and you have already 'dimpled' or put your flat spot on the shaft for the second set screw, i would run it with one, at lest to test it...

[StudEbiker]

Yeah, it's in the right place and dimpled and the second screw is loc-tited now. That was kind of my thinking as well AJ. Run it with one and see how it goes. This isn't a big watt build (36v30a) so hopefully it will be okay for awhile. I swear, if I can get this bike going I won't even THINK about putting together another bike anytime soon.........probably.

[Ornery]

Any reason why you can't drill it out? What size set screw? Use the correct size drill for the Minor Diameter of the tap. Use a tap to chase it after it's off. Irwin sells handy kits with the right size drill and tap in one reasonably priced kit at Lowes or local hardware stores, even Walmart. Might be a problem if it's metric.

The last set screws I bought were shorter than I wanted, because the hardware store was sold out of the longer ones. Now, I see that may have been a blessing in disguise. They really don't need to be that long, especially when using three, like I did.

As far as your post about stressing, why not buy extra parts, just in case? The shipping frequently costs more than these sprockets & shafts.

[StudEbiker]

I could do all that, but the screw is already set in the dimple on the shaft. Drilling it would be complicated to say the least. I would need a very long bit in a very small size which would be very prone to breaking if I could even find a bit the size I need in the length I need. Doubtful. I'm just going to run it the way it is for awhile. I think I will probably go in and put new bearings in and tackle this set screw issue in the near future, but first I just want to get it going and put a few miles on it and see what it's like. Yeah, I should order extras though it wouldn't have done any use on the #25 sprocket issue, but I should order some extra bearings so I have them around.

[liveforphysics]

Drill out and move up to the next size screw. A set screw can't have the same shoulder wall thickness around the drive socket feature without having a smaller diameter feature. When possible I try to use longer shank Allen head cap screws instead of set screws when it has the head clearence for it.

Dimple it, and you don't need a lot of tension to hold the torque load. Purple loc-tite is the weakest, I like to use it on set screws to give them a better chance of comming back out. This is why they call them set screws and not release screws though. Its not just you that struggles with them.

[Harold in CR]

If you have enough diameter, try sharpening a carbide tip drill bit on the wrong edge, so it tries to bite as you turn it backwards. Put all the down force on the drill before applying motor torque. These bits are quite a bit tougher than normal drill bits, and, the set screws are hard. That's why they strip allen wrenches.

I'm thinking your set screw screw might be too small a diameter. Left handed drill bits work pretty well removing broken studs. Much better than EZEE outs, that spread the stud even tighter.

[AussieJester]

The main problem i see is the size of the bloody things, as Luke (i think?) suggested the longer length ones might be better, i noticed that whats ThudSTeR used on the 2 speed box he made for me, i haven't had issue with those yet they are nice beefy f***ers too albeit imperial grrrrs @ Todd hahaha... Metric for the Winnnnnz



KiM

[StudEbiker]

Good advice LFP. However, now I have a new issue. I put everything together and I thought I had my fixed gear cog locked down with the set screws (though thankfully not loc-tited) and decided to go for a pedal only try out of the bike.

I felt some slipping as I was pedaling but only thought it was the freewheel tightening in it's thread on the other adapter. When I felt it slip a little too much I took a look and realized it was the fixed gear cog and adapter that had been slipping on the shaft.

I soon realized that the set screws had missed the dimples and had only tightened on the shaft and that is what had been slipping. Now with the set screws out on that adapter I can't get it to easily move or come off.

I think if I keep working with it I can get it off (or at least in place to tighten on the dimples) but it's definitely another "oh crap" moment.

[Thud]

There are days when you will be further ahead & accept a loss.
if it comes to it:remove the assembled shaft & slipping cog....drive the shaft out (galling the puke out if it prolly) & see if you can send the offending set screws through their holes into the shaft area with a slightly smaller drill bit. a drill will catch & drive it through normaly.

As a general rule I try to use the longest set screws that will fit the application..this usualy means replacement from the start & alle wrhenches are cheap compaired to the frustration of stripped set screws...grind the ends back to keep them sharp, & replace as required.

[StudEbiker]

There are days when you will be further ahead & accept a loss.

That really sums up what I'm feeling right now very well.

I've decided that I am making too many compromises with what I have done trying to do it myself without the right equipment and experience. I found a really decent fabricator shop locally last week so I am going to take it to them and have them put it all together right.

Today I can't get the outside most fixed gear cog adapter off the shaft, It got so much ground metal in between the adapter and the shaft it is just not going to come off. I think the fabricator will have to drill the 1/2" shaft out of the middle of it to gt it to come off. I thought if I could get it to start spinning on the shaft it would loosen it up so I could back it off.

I tried lots of turning and a little banging and it was only going FURTHER onto the shaft. Then I remembered what had caused it to spin in the first place which was riding the bike. Okay, I'll go ride the bike hard and hopefully that will get it to spin. No matter how hard I pedaled the adapter didn't move even a little bit.

So, I will take it to the shop and have them do everything the right way including putting some new bearings in because these all ready don't feel so great with everything I've had to do. I'll also have them put the long shank allen head bolts in the #25 sprocket.

It is going to cost me some more bucks and take some more time, but I'll have more peace of mind when riding and that will be worth it.

[Ornery]

Man, a shop is going to have to charge $50.00 per hour to mess with that. Sounds to me like a good excuse to buy more tools! Sears should have some hex drive drills in stock, that could easily be extended with an adapter. Drill those things out with a 3/16" or 1/4" bit, and re-drill and tap them larger with a 1/4-28 or 5/16-24 set screws or socket head cap screws. Once you've done a couple, it will go easier and you won't hesitate to do it in the future. Turn a small setback into a 10 minute repair, with an upgrade to boot. Oh, and new tools, too! Save your receipts for the drills in case they don't perform to your expectations.

A hammer with block of wood or urethane faced hammer ought to take care of that stuck gear cog adapter. Probably have to clean up the shaft with a file after it's forced out. Yet another tool or two to add to your ever growing collection!

[StudEbiker]

Man, a shop is going to have to charge $50.00 per hour to mess with that. Sounds to me like a good excuse to buy more tools! Sears should have some hex drive drills in stock, that could easily be extended with an adapter. Drill those things out with a 3/16" or 1/4" bit, and re-drill and tap them larger with a 1/4-28 or 5/16-32 set screws or socket head cap screws. Once you've done a couple, it will go easier and you won't hesitate to do it in the future. Turn a small setback into a 10 minute repair, with an upgrade to boot. Oh, and new tools, too! Save your receipts for the drills in case they don't perform to your expectations.

A hammer with block of wood or urethane faced hammer ought to take care of that stuck gear cog adapter. Probably have to clean up the shaft with a file after it's forced out. Yet another tool or two to add to your ever growing collection!

Yeah, that sounds like a good idea, but what you don't realize is that the freewheel adapter behind the stuck on cog adapter has a set screw that can't be removed while the freewheel is on it. So punching out the shaft is not as easy as it sounds. The shaft is probably going to have to be drilled out.

I've tried doing this myself, and I have pretty decent tools, but some things are better left to people with experience and tools the avg. Joe just doesn't have or have room for. It may cost me a little more, but in the end, it will be done right.

When you're not paying for the expense of maintaining a car, a couple of hours of $50/hr. labor is still pretty cheap. The shop I plan on taking it to will probably charge about $50 tops though because I won't be in a hurry and the guy can just do it when he has some time. When I went in the other day for a little work the guy was in the middle of building a $17,000 multi-head remote retractable shower head system.

He stopped working on that and fooled around with my thing for about 45 minutes and only charged me ten bucks. When your building $17,000 shower heads you're not gonna try and get rich off the guy trying to put an electric drive together on his bike. I think it probably helped that the owner of the place had a serious collection of collector bicycles in an upstairs climate controlled section of the shop.

[StudEbiker]

Well, after much drilling, beating, sawing, and cussing I have it all apart again ready to make a fresh run at it again. This time with the previously mentioned improvements. I'll probably still have the fabricator do a little work for me, but it won't be as much now.

[StudEbiker]

So I drilled and tapped the #25 sprocket and am planning on replacing all the set screws that I can with allen head bolts and I had an idea. Could I drill and tap the shaft as well so the bolts are actually threaded into the shaft instead of just tensioned onto the shaft? It seems like it would be much more secure and solid. Of course it might be tough to only thread through part of the shaft. I don't think I would want to go all the way through because of how much strength in the shaft I would lose. Is there any reason why I can't just put a hole (not threaded) deep into the shaft so there is a good part of the bolt imbedded in the shaft? Here is a picture illustrating what I mean. It seems like this would be better than just having a divot in the shaft.

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[amberwolf]

If the shaft is not hardened, you could physically do it, but you will significantly affect the strength of it against side-loading. If you have bearings on the outboard end of the shaft as well as the inboard, where the chaindrive comes from, then you wouldn't have to worry much, but with no outboard support, it will flex the shaft a bit more at the weakest point on each revolution, especially under higher torque levels, and at some point it will begin to fracture there.

[liveforphysics]

So I drilled and tapped the #25 sprocket and am planning on replacing all the set screws that I can with allen head bolts and I had an idea. Could I drill and tap the shaft as well so the bolts are actually threaded into the shaft instead of just tensioned onto the shaft? It seems like it would be much more secure and solid. Of course it might be tough to only thread through part of the shaft. I don't think I would want to go all the way through because of how much strength in the shaft I would lose. Is there any reason why I can't just put a hole (not threaded) deep into the shaft so there is a good part of the bolt imbedded in the shaft? Here is a picture illustrating what I mean. It seems like this would be better than just having a divot in the shaft.

collar.JPG

Now that's a set screw! That's how I've switched to doing things, at least for the proto-type stages.

I would grind/sand the head down to have a cone-like taper (try to match the taper of the end of the drill bit) and then dimple the shaft and thread her in snug. I see drilling the shaft resulting in potentially broken shafts pretty easily.

[Gordo]

[quote="StudEbiker"]So I drilled and tapped the #25 sprocket and am planning on replacing all the set screws that I can with allen head bolts and I had an idea. Could I drill and tap the shaft as well so the bolts are actually threaded into the shaft instead of just tensioned onto the shaft? It seems like it would be much more secure and solid. Of course it might be tough to only thread through part of the shaft. I don't think I would want to go all the way through because of how much strength in the shaft I would lose. Is there any reason why I can't just put a hole (not threaded) deep into the shaft so there is a good part of the bolt imbedded in the shaft? Here is a picture illustrating what I mean. It seems like this would be better than just having a divot in the shaft.

What you are proposing is a very bad idea. The shaft will probably break. That is why a flat on the shaft is used to secure a sprocket. It is the best of bad choices. A proper set screw has a serrated end on it, which acts like a lock-washer, securing it to the shaft. If I was doing this, I would use Loctite bearing seating compound on the entire shaft, sprocket interface, and set screw. To get it to release, you just need to warm it to @ 450*F.

[StudEbiker]

What you are proposing is a very bad idea. The shaft will probably break. That is why a flat on the shaft is used to secure a sprocket. It is the best of bad choices. A proper set screw has a serrated end on it, which acts like a lock-washer, securing it to the shaft. If I was doing this, I would use Loctite bearing seating compound on the entire shaft, sprocket interface, and set screw. To get it to release, you just need to warm it to @ 450*F.

I think the consensus here on the board is that a divot is better than a flat spot. I have read that in LFP's posts in the past and I believe him. I am also going to go with either Loc-Tite blue or purple which doesn't have to be heated to as high a temp. as red.

Okay, I guess I won't drill as deep into the shaft as I suggested. The shaft I am using is stainless so it has good strength and I think at the power levels I am planning to run I think it would last a long time, but I guess I'll just go with the divots.

How deep should I dimple the shaft though??

[Gordo]

SS, depending on what number it is, is neither as hard or as brittle as most steel shafting. It is more elastic and does not crack as readily as steel. I think what you have build is overly strong and you won't have a problem with it.
The very best system of locking sprockets and shivs to shafts that I have found and used for many years is the taper lock.
This is not the hardware I have used, but an example;
http://www.fptgroup.com/fenner.asp?title=&pageid=2664