Broke my steel rear dropouts

[lookingelectric]

Yes, I managed to break the all-steel rear dropouts on my mountain bike turned electric vehicle. I run a 5305 @ 56V which produces a lot of torque and found:

1) That I was rounding out the steel dropouts pretty significantly
2) That the right side dropout broke roughly in half

Luckily, I was riding with torque arms (2 of them) otherwise, I could easily have been injured.

Now, does anyone know of a good steel bike with thicker, stronger dropouts that would be appropriate for use with a very torquey motor?

 

[voicecoils]

how did the dropouts round out if the torque arms were in place?

Here's a beefy 4130 steel frame:
http://torpedo7.com.au/products/KWFRMN8ST
Click on the pic and checkout the other photos of the dropout area.

 

[lookingelectric]

The torque arms allow a little bit of play. In addition, I didn't notice for a while but the pipe clamps used to hold the torque arms in place were starting to pull, stretch and break as I rode.

how did the dropouts round out if the torque arms were in place?

Here's a beefy 4130 steel frame:
http://torpedo7.com.au/products/KWFRMN8ST
Click on the pic and checkout the other photos of the dropout area.

 

[Ypedal]

Were the axle nuts loose ? :lol:

Got pictures ?

 

[Zoot Katz]

Were the axle nuts loose ? :lol:

Got pictures ?

It sounds like it might be related to this wherein the axle was stripped.
[/url]http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=4082&p=60482#p60482[/url]

 

[Kurt]

Torque arms have to be a perfect fit with zero play or I don't see the point in having them on the bike.The torque arm shouldn't be open ended like some I have seen.I wouldn't make it from mild steel as its to soft.Stainless steel is a good choice as its hard/strong and wont rust.

The nuts alone should hold the toque if they are tight and have a nice parallel contact with the drop-out. A nylock - nut with a nylon insert is a good idea and even then a medium strength lock-tight thread lock product is a good idea.

I have to admit the machined flats on the crystalite shafts are a joke and the quality of the steal is very questionable.
Kurt.

 

[John in CR]

Why get a new frame when you can get the dropouts fixed cheaply and easily? While you're at it just have them weld some nice thick material, 3/8" or so, to form the repaired dropouts, and then you won't need to worry about unsightly torque arms anymore. Be sure the repaired dropouts fit the hub motor axle nice and snug. Even if they talk you into using very strong stainless, still be sure to use thick material, because thin material can cut right through a soft axle allowing it to spin even if the dropout doesn't give.

John

 

[dogman dan]

Gets tempting to weld the axle to the frame doesn't it? Bikes just aren't made for such heavy wheels. Tight nuts are crucial, but dammit, they strip the axle so easy!

 

[lookingelectric]

I hadn't thought of that. How would I go about finding a shop that could do that for me?

Why get a new frame when you can get the dropouts fixed cheaply and easily? While you're at it just have them weld some nice thick material, 3/8" or so, to form the repaired dropouts, and then you won't need to worry about unsightly torque arms anymore. Be sure the repaired dropouts fit the hub motor axle nice and snug. Even if they talk you into using very strong stainless, still be sure to use thick material, because thin material can cut right through a soft axle allowing it to spin even if the dropout doesn't give.

John

 

[safe]

I'm pre-emptively changing my dropouts. Any time there is a torque being applied above and beyond the standard torque it's a good idea to beef things up a little. I'll be using an 8-Speed hub.

I use a welder... you might just go to a welder and tell them to "get creative". If you find the right guy who likes what he does he might do it for very little and do a good job.

 

[knoxie]

Hi

It sounds like there must have been a lot of play between the drop outs and the axle for this to happen? in steel? :? pipe clamps are not sufficient either to stop the torque arms moving, they can hold something against the frame of course but they must not be used as the retainer for the actual force as they will move and break. I havent heard of anyone with a steel frame and torque arms doing this so I am a little surprised, Mild steel is ok to use as a torque arm you just need to use a min of 5mm thick or so and make sure its a super snug fit, if the drops arent and they allow movement you cant rely on the torque arms to take the strain.

I had 2 stainless steel torque arms on the BMX and they got rounded (looked like a figure 8 ) because the BMX had 12mm drops and the arms were being used to take all the torque. I would go with the other poster, simply get the drops plated with some nice thick steel and get a local shop to weld them, make sure they are a snug fit, you wont even need torque arms if they are thick enough.

Knoxie

 

[voicecoils]

It sounds like there must have been a lot of play between the drop outs and the axle for this to happen? in steel?

Perhaps it's an issue of what type of steel. Kmart MTB with stamped dropouts from chinese steel?

Or is it 4130 Cromoly like this bike's dropouts:

 

[John in CR]

It sounds like there must have been a lot of play between the drop outs and the axle for this to happen? in steel?

Perhaps it's an issue of what type of steel. Kmart MTB with stamped dropouts from chinese steel?

To me the issue isn't just the dropout material, because steel frames typically don't have thick enough dropouts for our use. The steel of some of these hub motor axles is also quite soft, so a thin but strong steel dropout can still be a problem by cutting into the axle. Once some play develops and all we see is the end result, it becomes a chicken and an egg thing as to what cause what. His are already broken regardless, and since it's steel it's an easy fix, and a permanent one if nice thick material is used. I suggest just finding a machine or welding shop, and head over mid to late afternoon with a cold six pack or two in an ice chest. It's an easy enough job using shop scraps that some cold beer might be payment enough.

John

 

[safe]

I'm experimenting with some angle iron being used as construction material for some dropouts. The idea is to get a wider contact area for the axle and in my case to narrow the width so that the slot fits flush with the dropout. My axles are really long, so I have the ability to do this. (short axles would not work)

As you can see... it's still an idea so far... :wink:

(not sure how well it's going to work yet)

 

[lookingelectric]

I've been out looking for a new bike and they all seem to have the same size dropouts. There are some aluminum cruiser bikes with larger droupouts but the metal is obviously not going to be as hard.

I've decided to post a craigslist ad seeking a welder who can add some strength to these things for cheap.

http://sfbay.craigslist.org/eby/lbg/915025358.html
Edit: Some twit on craigslist flagged my post. Heres the replacement
http://sfbay.craigslist.org/eby/lbg/916107456.html

 

[swampjeep]

too bad someone flagged your add, it says "ADD HAS BEEN FLAGGED FOR REMOVAL"
and is gone

 

[dogman dan]

I like that pic Safe! You could even put some bolts through the angles and clamp down on the flats of the axle like a vise. Brilliant.