Best way to repair my steel torque arm

[cwah]

hello

I have my bike with variable regen and needed a strong torque arm preventing any movement.

I've used 2 mild steel torque arm of 8mm with 6mm stainless bolt and it lasted well for a year or so.

But now it has split in half for one:

And the stainless steel bolt split in 2 on the other side:

I'm hesitating between 2 options to repair this:
1. Buy 5mm thick mild steel angle bracket: https://www.ebay.co.uk/itm/Mild-Steel-Angle-Equal-Unequal-Various-Sizes-Lengths-Angle-Iron/291739479215?var=590761552991
That way the angle bracket should be stronger against lateral force. Is mild steel good? Shall I get cold steel?

2. Buy a welding machine and spot weld back the steel bar in the area it split. But I don't know which machine to buy? Any idea?

Thank you

 

[Andy-Mat]

hello

I have my bike with variable regen and needed a strong torque arm preventing any movement.

I've used 2 mild steel torque arm of 8mm with 6mm stainless bolt and it lasted well for a year or so.

But now it has split in half for one:

And the stainless steel bolt split in 2 on the other side:

I'm hesitating between 2 options to repair this:
1. Buy 5mm thick mild steel angle bracket: https://www.ebay.co.uk/itm/Mild-Steel-Angle-Equal-Unequal-Various-Sizes-Lengths-Angle-Iron/291739479215?var=590761552991
That way the angle bracket should be stronger against lateral force. Is mild steel good? Shall I get cold steel?

2. Buy a welding machine and spot weld back the steel bar in the area it split. But I don't know which machine to buy? Any idea?

Thank you

WOW!! The parts look a bit "thin" where the holes were made, so no big surprise that it broke eventually. Wider would be better
Welding is great, but all electronics need to be removed from the bike, or the parts must be removed and welded away from the bike.
Welding is actually great fun and both normal steel and stainless are easy to weld with the right wire (MIG), so I personally would buy some thick stainless steel, with stainless nuts and bolts and make up a completely new arm. It will look far better as no rusting!
Over the 13 years I have owned a welder, I have saved many times its cost, and enjoyed using it! Do buy an automatic welding mask, they cost nothing nowadays and will save your sight!
I hope this helps.
Andy

 

[jeff St.Clair]

Yeah ..I think if you weld it , it's always gonna be a weak point ..I think I would make a new one out of some beefy flat bar Mild steel is tough enough some stainless grades can be very brittle . Drill two holes and file the flat between them to fit snuggly over your axle rather than drilling and bolting it with the set screws you have used....The drawing just a rough thing you might want to increase the width to 40mm..that where the strength is needed . and drill it where you need to match the mounting point on your bike ..A big fat washer that matches the diameter of the axle over this plate will also add to the strength

 

[wheeliepete]

As Jeff suggests, a one piece bracket is always going to be stronger, either drilled/filled or slotted with a pinch bolt. 8 x 40mm flat steel bar should be fine. Make sure the hole/slot is a good snug fit on the axle, any movement back or forth will cause wear. I think your setup prob. worked fine until one of them failed putting more pressure on the other, causing it too to fail.

 

[cwah]

WOW!! The parts look a bit "thin" where the holes were made, so no big surprise that it broke eventually. Wider would be better
Welding is great, but all electronics need to be removed from the bike, or the parts must be removed and welded away from the bike.
Welding is actually great fun and both normal steel and stainless are easy to weld with the right wire (MIG), so I personally would buy some thick stainless steel, with stainless nuts and bolts and make up a completely new arm. It will look far better as no rusting!
Over the 13 years I have owned a welder, I have saved many times its cost, and enjoyed using it! Do buy an automatic welding mask, they cost nothing nowadays and will save your sight!
I hope this helps.
Andy

How much would it cost to buy the whole equipment for repair? any link to buy?

 

[cwah]

As Jeff suggests, a one piece bracket is always going to be stronger, either drilled/filled or slotted with a pinch bolt. 8 x 40mm flat steel bar should be fine. Make sure the hole/slot is a good snug fit on the axle, any movement back or forth will cause wear. I think your setup prob. worked fine until one of them failed putting more pressure on the other, causing it too to fail.

Are you talking about something like this?

What steel shall I get? Is mild steel ok?

I need double clamping due to strong regen force. so it's either what i have now or bolt clamping

 

[JPGiant]

As jeff suggests - a one piece lump of steel with a close fitting slot is the way to go.
That original design is a disaster despite lasting over a year, to have less than 1mm of metal from the edge of a hole to the outside of a steel bar is ridiculous, plus you should use high-tensile bolts with Loctite.

 

[jeff St.Clair]

If you make the hole that your axle goes through a good fit so the axle can't slop about you don't need any bolts to clamp it drilling and bolting makes it weaker ..have a look at my drawing in my previous post (click it once to see it full size) you will to this on both sides ...to make it bomb proof

 

[JPGiant]

Unless I'm mistaken, it looks like the bike's chainstay has cracked - just above the top bolt of your clamp in first picture.

 

[Andy-Mat]

How much would it cost to buy the whole equipment for repair? any link to buy?

Are you asking about buying a MIG welder? I just picked one at about 250 UK Pounds off ebay, got lucky, it works great, but that was without the gas cylinder.
Though you can buy special wire for them nowadays, with the flux in the middle of the wire, then you don't need the gas and cylinder, to protect the weld when actually welding.....
I learned Stick Welding in the Royal Navy, over 50 years ago, and I can only say that both MIG or TIG are both far better to my mind.
Possibly a welder that can do both MIG and TIG might be the very best choice.....I had not heard of TIG till after I bought my MIG welder....
But let me be clear, not all MIG welders can do both, only ones specially made to do both!!
They are quite cheap nowadays, look through this:-

Mig & Tig Welder for sale | eBay

Find great deals on eBay for Mig & Tig Welder. Shop with confidence.

www.ebay.co.uk

I hope that helps.
regards
Andy

 

[cwah]

Are you asking about buying a MIG welder? I just picked one at about 250 UK Pounds off ebay, got lucky, it works great, but that was without the gas cylinder.
Though you can buy special wire for them nowadays, with the flux in the middle of the wire, then you don't need the gas and cylinder, to protect the weld when actually welding.....
I learned Stick Welding in the Royal Navy, over 50 years ago, and I can only say that both MIG or TIG are both far better to my mind.
Possibly a welder that can do both MIG and TIG might be the very best choice.....I had not heard of TIG till after I bought my MIG welder....
But let me be clear, not all MIG welders can do both, only ones specially made to do both!!
They are quite cheap nowadays, look through this:-

Mig & Tig Welder for sale | eBay

Find great deals on eBay for Mig & Tig Welder. Shop with confidence.

www.ebay.co.uk

I hope that helps.
regards
Andy

I just want something cheap for occasional repair. Not sure £250 would be cheap. Maybe better just to buy few steel bar

 

[cwah]

Unless I'm mistaken, it looks like the bike's chainstay has cracked - just above the top bolt of your clamp in first picture.

Yes that's why I need a strong torque arm!

 

[cwah]

As jeff suggests - a one piece lump of steel with a close fitting slot is the way to go.
That original design is a disaster despite lasting over a year, to have less than 1mm of metal from the edge of a hole to the outside of a steel bar is ridiculous, plus you should use high-tensile bolts with Loctite.

Is it high tensile bolt like this one?

M6, 6mm BLACK FULLY THREADED SET SCREWS HIGH TENSILE GRADE 8.8 HEXAGON HEX BOLTS | eBay

Hexagon Head Bolts. Black Self Colour 8.8 Set Screws / Hex Bolt DIN 933. All bolts are fully threaded. Thread Pitch - 1mm. Depth of Head - 4.1mm. Lets bring things together.

www.ebay.co.uk

I'm not sure what the grade mean? there are also these much more expensive but higher grade? Not sure it makes a difference:

Pardon our interruption...

 

[cwah]

If you make the hole that your axle goes through a good fit so the axle can't slop about you don't need any bolts to clamp it drilling and bolting makes it weaker ..have a look at my drawing in my previous post (click it once to see it full size) you will to this on both sides ...to make it bomb proof

I've seen this and I bought many many torque arm in the past with this slot design. There has also been some wobbling between acceleration and deceleration, which end up loosening my motor nut.

Even if it's a tiny play between acceleration and deceleration, the continuous movement just unscrew in few days or week the nuts. I just don't want to have this design anymore.

Clamping has been the most successful so far, no need to do any maintenance and no automatic unscrew over time.

I'd either keep the old design or have 1 plate with screw to clamp

 

[jeff St.Clair]

cwah ....Torque arms have been in use for years , if they are made accurately and well fastened to the chainstays and the drop out , they are bombproof ... it's not a slot ,its the shape of the axle and it fits the profile of the axle perfectly ,then a lock nut is tightened down .It cannot unscrew unless you take a spanner to it ... I think the clamping method is un reliable as it replaces the strength of 5mmx 30 or 40mm solid steel with the weaker strength of one or two 6mm set screws... but I would get the chainstay welded up before proceeding with this .. ...PS I'm very interested to hear more about variable regen . is it good ,can I get it for my self build e-rockhopper, what do I need? ... jeff...

 

[Andy-Mat]

I just want something cheap for occasional repair. Not sure £250 would be cheap. Maybe better just to buy few steel bar

They start much cheaper than that, that was what I paid for a very good home MIG unit. You should look through the link I posted, they start at around 50 UK Pounds. But I have not myself tested them.....
Usually the amps are quite low on cheaper machines, OK for thinner metal....
I would say at least 120 amps for home stuff.....
Old saying:- "You pays your money and you makes your choice"
Maybe someone else can advise on a cheap model.....
regards
Andy

 

[cwah]

cwah ....Torque arms have been in use for years , if they are made accurately and well fastened to the chainstays and the drop out , they are bombproof ... it's not a slot ,its the shape of the axle and it fits the profile of the axle perfectly ,then a lock nut is tightened down .It cannot unscrew unless you take a spanner to it ... I think the clamping method is un reliable as it replaces the strength of 5mmx 30 or 40mm solid steel with the weaker strength of one or two 6mm set screws... but I would get the chainstay welded up before proceeding with this .. ...PS I'm very interested to hear more about variable regen . is it good ,can I get it for my self build e-rockhopper, what do I need? ... jeff...

I hear what you say and non clamping torque arms works very well on non regen bike, but I've spent few hundred pound in the past buying all model of torque arms from dr bass hardened one to many others and ALL end up with tiny play leading to gradually unscrewing the motor nut.

As I speak now, I don't even need to make it, I still have few spare torque arms I could file to increase the motor hole trying to make the hole match perfectly my motor axle.

However, I'm really now confident about that especially because it seems that you're not a user of variable regen motor...

You should try it, you just need a direct drive motor with a variable regen controller. I have 1 throttle for acceleration and 1 for deceleration. I almost don't use my brake anymore and now change my brake pad every year or so.

Few controller do that such as the phaserunner, kelly controller, sabvotton, etc etc

 

[vfr400]

Mild steel is best because it's more resistant to metal fatigue. I wouldn't weld anything because you're much more likely to get metal fatigue in the welds.

Is it high tensile bolt like this one?

M6, 6mm BLACK FULLY THREADED SET SCREWS HIGH TENSILE GRADE 8.8 HEXAGON HEX BOLTS | eBay

Hexagon Head Bolts. Black Self Colour 8.8 Set Screws / Hex Bolt DIN 933. All bolts are fully threaded. Thread Pitch - 1mm. Depth of Head - 4.1mm. Lets bring things together.

www.ebay.co.uk

I'm not sure what the grade mean? there are also these much more expensive but higher grade? Not sure it makes a difference:

Pardon our interruption...

High tensile can be worse because it suffers from fatigue more than MS. What he needs is a bolt with the correct length shoulder that runs nearly all the way to the nut. I would use mild steel bolts.

 

[vfr400]

Unless I'm mistaken, it looks like the bike's chainstay has cracked - just above the top bolt of your clamp in first picture.

I think what you're seeing is the join between the hanger and the frame. Nothing to worry about.

 

[cwah]

Mild steel is best because it's more resistant to metal fatigue. I wouldn't weld anything because you're much more likely to get metal fatigue in the welds.

High tensile can be worse because it suffers from fatigue more than MS. What he needs is a bolt with the correct length shoulder that runs nearly all the way to the nut. I would use mild steel bolts.

Thanks. I was thinking to buy these parts:
This 25x25x5mm:

Mild Steel Angle - Equal & Unequal - Various Sizes & Lengths - Angle Iron | eBay

Find many great new & used options and get the best deals for Mild Steel Angle - Equal & Unequal - Various Sizes & Lengths - Angle Iron at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk

Clamped with this high tensile bolt 12.9:

Pardon our interruption...

The only mild steel bolt I can find on ebay are these

M6 - 6mm HEX CARRIAGE COACH BOLTS MILD STEEL ZINC DIN 603 FS1608 | eBay

6mm M6 COACH BOLTS HEX CARRIAGE SCREWS MILD STEEL ZINC DIN 603/555. 6mm M6 Mild Steel Coach Bolt with Hexagon Nut. DIN 603/555. Standard DIN 603/555. Bright Zinc Plated. Material BRIGHT ZINC PLATED. UK Orders.

www.ebay.co.uk

And they don't give me much confidence they'll last