GT i-drive 2.0 Build

[GCinDC]

I needed to buy myself a Christmas present!

I've been hunting for DH bikes and this one came up on Craigslist for $350, with a bunch of extra goodies, including the upgraded Marzocchi Jr T Bombers.

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Issues to tackle before the maiden voyage:

- Battery location, mounts (if any) & case
- Controller mounting location?
- Custom rear rack? mounted only to rear wheel stays
- Rear brakes: Refit with rear V-brakes so I can attach the Burley trailer.

And last but not least, the issue I need help on right now:

- Torque arm mounts
As you can see, the rear dropout is very curvy. And I'll be hoping to use regen, so I'll need it two-way.

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If I didn't have regen, would this work?

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Here's my current torque arm setup

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[GCinDC]

I should add that in the top photo, the white thing taped on are two emtpy 14" long Hyena@boxes, rectangular PVC gutters cut & shipped by from Australia. Thanks, Hyena!

I'd been planning on mounting them up by the stem, but my knees would catch them.

So battery location is TBD.

On paper, my 8 lipo packs will fit in the triangle, but in the real world, I think it'll be too tight. The cables and guides are on the side and in the way of slipping a pack in. I attach/detach my current one daily, so I'm not looking for a battle. I want this to be 'designed'.

I've got some graphics of ideas, including downtube mounts. I'll post those later.

The battery case and torque arms are top priorities.

Love to hear your comments & suggestions.

[dbaker]

What a great Christmas present! So the outstanding characteristics of this bike are long travel front suspension and high speed stability? Is it a longer wheel base than your standard mountain bike?

Dave

[GCinDC]

What a great Christmas present! So the outstanding characteristics of this bike are long travel front suspension and high speed stability? Is it a longer wheel base than your standard mountain bike?

Dave

Yes & Yes! Seems about 3-4" longer, which should help at high speeds, as will steering.

I wanted full suspension, but actually started to buy all the parts to outfit my comfort bike w/ disc brakes. That was my #1 priority. But all the parts kept adding up, so it seemed like a full bike at a great price would be a better deal.

Priority 2: Full Suspension. Hitting potholes, which will get worse through the winter, would be nasty w/o the rear supsension.

Priority 3: Strong Frame! Weight's not a big issue. Why spend money for a lightweight design, when a motorcyle would be better built?

Priority 4: Double-wall front wheel, pretty much standard on downhill bikes...

I love the way it feels!

[GCinDC]

I've got to confess, I don't understand how those two piece torque arms work... unless they're designed primarily for use w/ front forks.

For the rear, they don't make sense, do they??

Part of my challenge is making a torque arm that works in both directions (to support regen) AND has multiple planes.

If I could machine the stainless steel, which I'm not eager to do, this might work as one plane IF I put washers to stand it off from the dropout enough that it's flush with the rear disc mounts:

gt_torque_arm-1.jpg (58.06 KiB) Viewed 14411 times

I probably WON'T need to use the rear disc brake, since: A) the Burley trailer mount would hit it, B) I'll enable regen and C) I'll use Vbrakes on the back.

A design like this would be nice because:

- it would virtually eliminate my FEAR that the wheel will ever drop out.
- it would be relatively easy to remove

So questions:

- If I drew up such a design, where could I have it laser cut?
- Or would 1/8 mild steel work fine? I'd be happy to cut that up.
- Would one be enough for say, 100V 40A on the 9C?

Thanks,

Greg

[ambroseliao]

Hi GCinDC,

My concern with this bike is the less than robust dropouts on it. Your idea of a double torque arm is a good one (IMHO). There are too many voids and stress points in the stock dropout. I would suggest extending the arms so that they travel further up both stays reinforcing the welds on the stays. You're putting a lot of stress on those stays and dropouts. Make them as strong as feasible to do.

Just a thought.

Ambrose

[GCinDC]

I agree it does look wimpy. But how could that be for a downhill bike??

It will have more weight and more torque than it was designed for. Hopefully if I just avoid the 10' drops...

[dogman]

Yeah, I'd pay 350 for that.

Definitely time to design something for a machine shop, or yourself to fabricate. But two tourqe arms stacked, one each way, ought to work if the axle is long enough to still get a nut on it.

[skeetab5780]

i ride a gt avalanche with very similar dropouts at 48v. have over 1000 miles on it so far. may look wimpy but its holding up perfectly...i dont ride gentle either i offroad frequently.

[justin_le]

I've got to confess, I don't understand how those two piece torque arms work... unless they're designed primarily for use w/ front forks.
For the rear, they don't make sense, do they??

Absolutely correct. I designed this torque arm style just over a year ago 100% for use on front forks. It was never intended to work on the rear and no consideration was given to accommodate that. The idea was that if the axle torque cause the torque plate to pivot about the bolt, it would simply sink itself further into the dropout slot. For this to be the case, the torque arm needs to be installed on the back side and not the front side of the fork.

I've seen people attempt to install it on the rear wheel with the torque arm hose clamped to the under side of the chainstays. In this arrangement, the torque plate will tend to rotate the axle OUT of the rear dropout. Not a good setup.

- If I drew up such a design, where could I have it laser cut?
- Or would 1/8 mild steel work fine? I'd be happy to cut that up.

I think we demonstrated pretty clearly that 1/8" steel doesn't cut it for resisting axle spinout torque. Used at least 3/16" or 1/4" metal plate. Most cities will have a facility or two that will do waterjet cutting for you at a reasonable rate.

-Justin

[GCinDC]

I designed this torque arm style just over a year ago 100% for use on front forks...

Brilliant design for the front, Justin!

Am I on the right track for the rear? Do you have any designs for that, or does it all depend on the individual dropouts?

I just found your amazing torque arm thread. Great stuff. I've got a lot of ideas to explore now.

[tartosuc]

hi,

be carefull with that frame, they are famous for craking at 2 places, i have a feeling that the rear hub motor could make it worse. make sure you inspect that farem after every ride.

[Mark_A_W]

I agree it does look wimpy. But how could that be for a downhill bike??

It will have more weight and more torque than it was designed for. Hopefully if I just avoid the 10' drops...

It's not a downhill bike.

It's a cross country dually fitted with downhill forks. It will need a 6mm triangular plate on either side as torque arms, securely attached to the frame.

[GCinDC]

thanks for the feedback about the bike. i'll check the frame, but will mostly be on the street so hopefully it'll be as strong as my comfort bike..

dogman, i like your idea about two torque arms mounted each way.

and from the research, and other comments, 1/4" steel seems to be the ticket.

would 2 x 1/8" torque arms fastened at 90 nm fit the bill? or was 90 nm just for steel forks? what's the safest for aluminum forks?

[nicobie]

I think Justin's torque arms will work fine IF you weld the two pieces together after you determine the angle they need to be. Put one on each side and you will be golden.

.

[GCinDC]

I think Justin's torque arms will work fine IF you weld the two pieces together after you determine the angle they need to be.

Good idea. Think I can weld stainless steel w/ my Lincoln wire-feed welder?

In other news, I found a waterjet cutter near DC. Rough quote: $75

At hand, I have one of Justin's and two shorties.

The shorties actually have a lot of play, but if one is adjusted tight to counter acceleration and the other is adjusted tight for regen, and the nut is on tight, it should be better than the tiny bit of play in a single torque arm, no?

I'm figuring I'll stand it off from the dropout w/ a washer, in fact, probably one of the ones with the tabs, that I'll smash down to act like a key in the bottom of the dropout.

[nicobie]

I think Justin's torque arms will work fine IF you weld the two pieces together after you determine the angle they need to be.

Good idea. Think I can weld stainless steel w/ my Lincoln wire-feed welder?

Probably not.

However you might be able to drill and use a roll pin on them. It all depends what kind of stainless they are made of.

[GCinDC]

It took all of my patience to wait this long... and a solid day of putting it together. I'm using dual torque arms, even tho I don't have regen yet.

And I finally had my 'DUCT TAPE' ride today...

O H M Y G O D !!!

First sensation of seeing front tire out in front was awesome...
Handling is so much easier with the extended wheelbase.
The cush of the suspension means no longer worrying about the little bumps in the road. (and while the original GT seat looked cool, it was hard...
And new with this build, I bought from methods an 11T cog (on a 7spd freewheel). Even with a small front ring (not even 48T?), I have resistance while pedaling at high speeds!

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Printout from Powerpoint: For the 'triangle', I took an online image of the bike, scaled it, drew lines around it. Then I created scaled boxes for the lipos and put them however they'd all fit.

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I decided a structural shell was needed for the bottom & rear support, to keep the lipos from getting mashed by the tubes. I would have loved to wrap it all the way around, and make a front corner loop for locking/carrying, but it was all just too tight. I even had to cut more off of the bottom side to be able to slide it in.

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I made flap on top to mount my db25 balance connector (with BM6's for discharge & paralleling connector for charging 5s @10 A).

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As you can see, I've got some work to do to proctect this situation, but not bad for a days work...

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Next steps:
- Find/Buy GT V-Brake posts for rear - Or buy thread on disc and make an adapter to make it fit. -- no rear brakes right now ---
- Enable Regen (I've got the cable and the program installed, but I need to research all the setting to make sure I don't blow the controller.)
- Tape lexan to the sides of the battery pack.
- Make a loop on the pack for locking
- Waterproof the controller - wouldn't it be nice if there was a rubber housing for all the wires that come out?
- Rig up accessories

[dbaker]

Cool! Is that aluminum from a street sign?

Does the rear suspension squat when you gun it?

I have got to get a DH bike!

Dave

[GCinDC]

Is that aluminum from a street sign?
Does the rear suspension squat when you gun it?

Yep, great recycling, huh? I love aluminum. It's hard, cuts like butter, but it's tough to bend... Unfortunately, it's pretty thick and i don't have an extra 1/8" to spare in the frame triangle. I got some weldable steel sheet that is thinner. I've started working w/ it, but I don't like it as much... More on that later.

And no, the suspension doesn't squat when I gun it. It is harder to do wheelies though...

Lotta work done this weekend:
- removed rear derailer wire and lever/brake combo. replaced w/ ebrake lever.
- replaced front mechanical disc brake w/ hydraulic kit
- tried to disconnect front disc lever/shifter combo but couldn't! i want just the shifter (in case i lose battery power, i'll need to be able to pedal w/ front gears). i was eyeing a simple lever on another bike, and started to take the integrated unit apart, wasn't fully committed, and didn't want to remove all the screws and never be able to put it back together...
- tried to fit new rear disc brake on but failed
---> not enough room beside motor for caliper to fit w/o rotor scraping bottom bracket arm(?)
---> would have to carve too much material out of caliper mount (1/4" leaving only 1/8"?) (and not sure how to do that).
---> burley trailer hitch would hit rotor, and don't have time to make a new hitch
---> so no rear brakes yet. back to plan B: going to try to find/buy V-Brake posts that fit the GT and use the minimal regen I've got now and go slower...
- spent A LOT of time trying to install/program my 846 infineon controller. took 5 days to get the driver working. and now i get runtime error every time i try to flash it... more on that later.
- started building new battery case w/ weldable sheet metal
- carved new torque arm out of 1/4" steel bar. i'm leaving it long until i figure out what else i might want to attach to it, if anything. behind it there's one washer on the axle and two washers behind the bolt, so that it's perfectly square to the axle. that bolt goes through the bike disc brake mount hole and into the disc brake mount itself. i used that piece because it's sturdy, has deeper threads than ordinary bolt, acts like a washer, and is also bolted to top mounting hole too, doubling strength.

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[GCinDC]

Some bad news on the bike. The head tube is loose; might need a new headset if it's not been too damaged. When I hit the front brake, it jerks back. Probably another reason for the cheaper pricetag. I'm going to try to have it repaired.

The battery pack in the triangle is fantastic. It feels so solid and secure in there. I just have one piece of gorilla tape wrapped over the top tube to keep it from sliding and it never budges.

Takes curbs like a cat.

Still working on programming. Getting a new cable soon.

And this is definitely off topic, but since I know people only care about pictures, here's a 3D sonogram of my third child, due Jan 23, but could come any day now...

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[GCinDC]

PHEW! Got it Programmed. No thanks to Vista...

Tried a bunch of settings. Riding with this now:

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Disappointed w/ level of regen. Same as what I've been seeing: -5A max. EBS level must have already been set to 2.

I set Slip Current Charge Mode to: 1: Fake only indicate, so that braking activates it and I can coast, but it doesn't increase strength, and I've come to like it always on when throttle released because I'm always accelerating or decelerating, and it feels safer to hold the throttle and not reach for the brake. So I set it back to 0.

Upped the Phase & Rated Amps. Max before was 35A. Now I see 40A. I notice it's got hotter too. The traces aren't very beefy at all, so I'll have to keep an eye on it.

Bottom line, I think the days of this controller are numbered. I'm starting to search for some 116's..

But it's nice to finally get it programmed.

Huge thanks to Methods (for cable & support) and Mike for support!

[GCinDC]

Programed at work today on my work XP box...

Ride home was awesome!!! More Amps were noticeable. 40A is sweet, and gives me a taste for more.

Might have to beef up the traces this weekend. Should allow for more regen too.

Funny to get only 1 mile per 1Ah...

With the 48V ping I got close to 3 miles per 1Ah.

I'm losing some range but the miles are getting more fun! And since I've got a 5 mile commute and a 10Ah pack, I might try to get lost in the woods on the way -- as soon as I get new fenders. Spleaach.

My last ride in the rain, (w/ controller/pack wrapped in plastic bag), I got totally friggin soaked from the front wheel. The nobby tires kicked up all kinds of grit into my mouth.

Oh, and good news from my friends at revolution cycles: V-Brake Posts! It was an odd fit. Three shops didn't have them. So now I can attach the rear brakes!

[Hyena]

Your battery frame / box looks good. You couldn't make use of the PVC ?
Don't worry about the duct tape, many of us have travelled hundreds of miles with little more than tape holding our batteries in / on! Hell I rode for over 1000 miles with my battery box strapped to my top bar with an old inner tube

[GCinDC]

Your battery frame / box looks good.

What box? You mean the aluminum bottom support? Who needs a box anyway? Just smash and mold the lipos into whatever shape you want, right? Hahaha.

You couldn't make use of the PVC ?

Was going to. Very snug w/ my wires, but there were two issues:
1. where i could best fit them, under the down-tube, they were liable to get hit by the tire if the fork bottomed out
2. making supports for a box that hangs from the downtube (as in 1st photo), and doesn't shift is no small challenge. i was eyeing the waterbottle holes to anchor them, but when push came to shove, and i found i could tape them into the triangle, and see how snug they are. trouble ticket closed. i just need a little more shell and waterproofing...

Don't worry about the duct tape...

I wouldn't be anywhere w/o duct tape. But let's be clear. Not ordinary duct tape. Gorilla tape. This stuff is freaking awesome. Sticks to anything. Peels off easy. Stays sticky so one piece can be used over and over and over. It's structural. I can't believe how strong it is.

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Now, for the picture of the day... I was happy to see that it snowed last night! After my last soaking ride w/o fenders... this morning I gorilla taped my old front fender on. And had to do some quick waterproofing.

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Still got a salt-water shower, but much less than before.

Note the new rear V-brakes.