I keep busting forks

[Electrobent]

Hello all, I'll be back soon.  My machinist made me new front forks.  I'll post a picture soon.  Regen is really hard on standard forks with brazed in dropouts--the forward and backwards forces quickly fatigue the brass brazing and the drop outs "dropout."  Fried controllers can do that too .

We tried welding in open ended wrenches but they were not deep enough so this time he made a cap for the end of the dropout (which he also made out of 1/2 inch stainless) which screws in so that the axle is completely surrounded.  He says that the next thing to break will be the top tube of the front forks where it enters the headset from the bottom.  I am beginning to think that regular bicycle stuff is just too wimpy for a 1000W 48V regen setup.  I had no problems with 500 watts at 36V and no regen.  I'll put it all back together and if I don't break it at 48V, I'll go to 72--maybe that will be enough to do my 20 mile commute?

[Bikemad]

Hi Eric, you'll have to post some pictures of the finished item for us all to see.

Have you tried using a bolt on torque arm (or preferably a pair of them) on any of your forks? Because this should take the torsional load away from the brazed joint.

Regarding your proposal to increase to 72V to extend your range, perhaps it would be safer to increase the capacity of your pack instead of the voltage.  This would directly increase your range, without increasing the torsional load on the front wheel axle .  Switching to 72V would put 50% more load on the axle fixings under full power, but the regenerative braking force would be less than it now is with your existing 48V pack.

Doubling the capacity of the battery will give twice the range, but doubling the voltage will not:
Higher voltage = higher speeds = more losses due to friction and drag = reduced efficiency!

My range is almost halved when I configure my 30V 10Ah LiPo pack to form a 60V 5Ah pack, although I must admit that it's a lot more fun with 3kW than it is with 1.5kW.

Alan
 

[Electrobent]

But the problem is that the NiMH batteries want to be series for charging and regen purposes.

I can always turn the top speed down on my Infineon controller.

You said that regen would be less at a higher voltage, I am assuming that this is because the difference between what is coming out of the motor (generator) and the what is in the batteries is less.  If this is true, then maybe additional voltage would make for less stress on the steering tube.

[Electrobent]

Here's a pic of the welded on wrenches that did not work along with the new and yet untried set-up.

[Bikemad]

Eric, those clamps should certainly stop the axle from turning 100%, let's hope the forks have not been adversely affected by the localised heat generated by the welding process.



Alan
 

[Electrobent]

He heated and cooled the whole bottom section.

He had even more ideas but they were dependent on knowing exactly what the metal was and how it was treated.  I told him it was probably Chrome Molly but had no idea if it were annealed or not.

[Electrobent]

the new forks lasted through a short test-ride!

[Leslie]

Rear hubs if your big dude, and if youre a huge massive momma, dual motors are a must.

Always install your brake swtiches so youre not operating the hub and braking at the same time..   Do not heat treat where it enters the head set.  slightly bigger bag tires on forks with null suspension might be worth a look too.

[GM Canada]

Rear hubs if your big dude, and if youre a huge massive momma, dual motors are a must.

Hey who you calling a huge masive momma!

Gary

[SydneyCommuter]

It's not about weight (not entirely) its about roaring off up the steepest hills leaving 1human power guys eating dust! And I mean roaring, love it! Definitely leaves a smile on your dial!

[MonkeyMagic]

Wazzzuppppppppppppp (spellchecker?? lol)

Has anyone found any decent front suspension forks with at least steel lowers?

I can't remember how long I've been looking for, but I am seriously sick of only riding on the road and like a grandma at the same time because my forks cannot cope with my spaceship lol

It's really not cool lol. I've been riding other bikes instead and I feel so bad for neglecting this one...

So any tips for around or under $300??

I didn't wanna create a new topic, but maybe it needs one for Fork choices. I mean something someone can go online or access at a bike store.

Honestly thinking I might go without suspension if there is a suitable fork.

Nearly bought a 'monarch springer fork' the ones that have been beefed up a bit for motorised bikes, but its not really suitable for my ride....

Anybody use, or even know of any motorcycle fronts that I can adapt to a threadless 1" headstem?

Cheers

Edit>>> Oh I just found these.... Hmmmm they indicate good strength with the dropouts welded from the bottom then up the middle, rather than on the side like weaker ones. Hmmmm


http://custommotoredbicycles.com/forks_springer_chopper

[Leslie]

Ive still got one of those 20" Dyno bikes.  The forks on them were decent enough.  Short and stocky.

There are plenty of suspension forks out there that can do the job, but they can be very pricey.

So might be better to start from a complete unit.

I bought this Diamondback from Big W and it is still hung together after horrible abuse.

http://www.bigw.com.au/toys/bikes-skates-scooters/bikes/adult-bikes/bpnBIGW_0000000246792/diamondback-recoil-66cm-men-s-dual-suspension-mountain-bike

I can only speak for this model but both the front forks and rear forks (rorks) droputs are steel and just the frame triangle is alloy.  I just magnet tested my frame and I must say for a BigW bike these forks are pretty awesome.

A bit expensive but this DiamondBack has all the perks.  Dual disks, dual suspension, both rear and front steel dropouts.  Id magnet test to make sure this hasnt changed before purchase..

Ill get the old camera out and get some close ups of my forks and rear dropouts.

[Leslie]

A noice set of steel forks!   



I originally assumed they were alloy, because of the description on the BigW web site.  And I though I'm not using a front hub so it didnt matter so much.

If these were alloy, looking at the size of them, I would say no to using a front hub, but I find they are indeed 100% steel from head to toe. They are rather more robust than standard steel forks you get with the wall mart bikes. Adequate for the job of supporting a front hub, but not stellar. I couldnt advise a torque arm, I would say you'd have to design your own. 

[Leslie]

Closer pic of the dropouts..

Looking a little weathered.  You can see the a little rust near the shocky bottom hole..  Iron Oxide.

[MonkeyMagic]

Oh cool, this is the bike you arn't using anymore and were intending on donating some of the parts right? hehe

Yes well my forks are similar, they are about 40-50mm travel only - which is the problem.

I have decent steel suspension forks if I did not have a kilo or 2 adding to the downforce when I hit a bump.. So I either need more travel, or none at all

Maybe I should just weld a flat piece of steel to mine instead and make them non-suspension lol

I say that because I would rather do that than remove my dashboard/cowling etc.