The Grinhill Mk2 RC-motor drive

[Grinhill]

Thanks Luke, I agree that would be ideal. The main reason for keeping the load-side roller is that I ran out of room on my present motor bracket to keep the belt down lower.

Note on this photo where the belt was previously rubbing the frame, due to very tight clearances and angled frame tubes.

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[liveforphysics]

In that case, slick way to solve the belt rub problem, and the belt skip problem I had figured you had a good reason, as most of the things you do are well thought out and well excecuted.

I think your bike build is a fantastic example of what an RC powered bike build can be.


Spinningmagnets- Go for a lower KV motor. It simply makes the most sense.

[Grinhill]

It's funny how we do silly things, even when we know we shouldn't. Like mixing water and electricity.

I blew up my controller yesterday, after a heavy rainstorm. I rode home, and the motor started jerking around and lost power. There was a lot of water still on the road which was thrown up.

So I switched off, pedalled home, then looked at the damage after I got inside.

rc_proj 101s.jpg (58.04 KiB) Viewed 1084 times

Looked like the water ran in along the 3 motor wires. I mopped up the obvious water, blew some air through to clear the water, and thought I'd give it another spin. Silly me.

The motor still jerked backwards and forwards a few times, then a little flash from the innards and a funny smell told me that the magic smoke had been set free.

I then did what I should have earlier, and took the lid off. There was some muddy water wicked between the case and the pcb, and now some blackened looking components.

[liveforphysics]

Clean it up and send it back to HC Tell them it burned up and caused your $2,000 helicopter to crash

[gunthn]

OOps

I ruined two of those and never got a response from the company. Oh well.

[spinningmagnets]

I've read that a lot of guys like to upgrade certain parts on the guts of these fickle beasts, but once a builder has the device working just they way he wants, is it advisable to fill the insides with potting goop? perhaps with aluminium heat-sink fins embedded on both sides? (never done this myself...just askin)

http://www.intertronics.co.uk/products/opt7020.htm

[grwsaltspring]

How do RC boats deal with water ? Is there anything to be transferred to bikes in the rain?

Greg

[recumpence]

I have gotten MANY RC components wet and merely hosed them down (internally) with WD40 and let them dry for a day. Almost always they come back to life.

RC boaters typically mount their components inside encosures. The ESC and motors are watercooled through sealed water tubes. That way they can seal up the components without heat issues.

Matt

[Grinhill]

I've been using my 25V 80A controller for the past few weeks (from my first build). Power is around the 1200W mark, and speed is noticeably less. I also have to use my 6S battery which is only 5ah, so back to recharging at work.

On the upside, I'm probably getting fitter than when running the higher power rig.

Hobbycity has received the unit back, but they are out of stock of replacements. Will wait and see what happens.

[mwkeefer]

I've been using my 25V 80A controller for the past few weeks (from my first build). Power is around the 1200W mark, and speed is noticeably less. I also have to use my 6S battery which is only 5ah, so back to recharging at work.

On the upside, I'm probably getting fitter than when running the higher power rig.

Hobbycity has received the unit back, but they are out of stock of replacements. Will wait and see what happens.

Grinhill,

So basically your running on a 6S pack just above the legal power limit in the US. What is your top speed at this power level, how is the hill climbing?

Honestly 1200w on a light weight bike would be enough for my skinny ass to run to the market or LBS and on a folder it would be quite adequate for commuting to and from the train station.

All on 6S packs? I don't know what your efficiency at this power level is? but heck... I have about 6 6S packs laying around here (broken down from a previous 12S3P pack) and 1200w @ 10-15AH sounds good (and light).

-Mike

[Grinhill]

Hi Mike
With pedalling, this setup does 42 km/h on the flat and 32 km/h up a 10% grade. Uses about 8 Whr/km downhill and 13 Whr/km uphill.

Unfortunately I only have one 6S pack, which I almost cooked yesterday, drawing 4.6 Ahr from it on the uphill run. It was very warm, and had expanded noticeably. I clamped the sides togethr as it was cooling, and it charged back up OK. 10 or 15 Ahr would be much better!

[liveforphysics]

Hi Mike
With pedalling, this setup does 42 km/h on the flat and 32 km/h up a 10% grade. Uses about 8 Whr/km downhill and 13 Whr/km uphill.

Unfortunately I only have one 6S pack, which I almost cooked yesterday, drawing 4.6 Ahr from it on the uphill run. It was very warm, and had expanded noticeably. I clamped the sides togethr as it was cooling, and it charged back up OK. 10 or 15 Ahr would be much better!

You're a wise man to clamp that pack. Pressure on the pack reduces the spacing and gaps between those hundreds of layers of copper foil and aluminum foil, and lowers Ri a bit, so packs run cooler. Looks like somebody needs to splurge on some 30c LiPo, or at least run another pack in parallel with that poor lone over worked pack

[mwkeefer]

Grin,

That's not too bad on a single 6S pack!

Luke has a point... it may be time to sink another 59 into a new pack...

also as odd as this may sound to some people, I have begun using 2 pieces of 1/16" ABS plastic when I build my packs... I clamp the packs within these ABS plastic "end caps" really just rectangular pieces the length of the packs then I wrap them in extreme duct tape before releasing the clamps.

End result is that since Ive begun this "process" (ghetto as it is) i've not had a single expanding battery due to heat and the temperature of my newer packs is 10-15 degrees f cooler than my old loose sided packs.

I assume this is due to the factors luke mentions above but I had no idea when I started doing it, I just didn't want to see the outter cells swell anymore = )_

-Mike

[Grinhill]

Thanks guys.
The plan for my next build is to buy four 6S packs, and then combine them with my existing 8S2p pack to build a 4p10s pack.

This pack is my very first LiPo pack. It's already served me very well, even if it died tomorrow. I'm going to regret writing that aren't I?

[amberwolf]

It's already served me very well, even if it died tomorrow. I'm going to regret writing that aren't I?

I hope not! But if it does, can I buy the BMS from you?

[liveforphysics]

Grin,

That's not too bad on a single 6S pack!

Luke has a point... it may be time to sink another 59 into a new pack...

also as odd as this may sound to some people, I have begun using 2 pieces of 1/16" ABS plastic when I build my packs... I clamp the packs within these ABS plastic "end caps" really just rectangular pieces the length of the packs then I wrap them in extreme duct tape before releasing the clamps.

End result is that since Ive begun this "process" (ghetto as it is) i've not had a single expanding battery due to heat and the temperature of my newer packs is 10-15 degrees f cooler than my old loose sided packs.

I assume this is due to the factors luke mentions above but I had no idea when I started doing it, I just didn't want to see the outter cells swell anymore = )_

-Mike

I've been doing the same thing 5lbs of tension on the electrical tape as I wrap a stack of packs, and I do 10 wraps in 4 places. It works out to be 200lbs of clamping force on the cells.

I played around with an old seriously abused (drained to 2v, over charged to 4.5/cell, lol) helicopter pack that was badly puffed. It was more like a sausage than a brick. lol. I hooked up my ghetto halogen bulb load bank with a voltage meter on it, and put the pack into my vise and started putting some pressure on it. The saggy voltage jumped up like 2 full volts when I put some squeeze on the layers I worked it out to have cut Ri by something like ~80% over no clamping on the poor damaged pack.

Packs like to be squeezed Just not so hard that the layers short inside

[liveforphysics]

Thanks guys.
The plan for my next build is to buy four 6S packs, and then combine them with my existing 8S2p pack to build a 4p10s pack.

This pack is my very first LiPo pack. It's already served me very well, even if it died tomorrow. I'm going to regret writing that aren't I?

Running cells in 4P is going to feel great. Say good-bye to voltage drop

[Grinhill]

I hope not! But if it does, can I buy the BMS from you?

BMS? What BMS? These RC Lipo packs are just slapped together and shrinkwrapped aren't they? The balance connectors are just tappings to measure cell voltage and do low-current charging at cell level, the smarts are in the chargers.

[amberwolf]

Ah, I didn't know that. I was just joking anyway (mostly--I *am* looking for BMSs that can be used for LiPo packs built from 18650s, preferably ones people might have tossed anyway due to being cooked or otherwise damaged but might still be repairable, because I might be able to afford those as opposed to new ones).

[recumpence]

Grinhill,

Your drive and what-not should be at your house within the next couple days. It shipped last week.

Any progress other than waiting on the drive?

Matt

[Grinhill]

Thanks Matt, check the thread in Ebikes Photos/Videos (although nothing recently). I had it over there so some of the hubmotor guys would be more likely to see it!

[Grinhill]

My replacement HV100 from Hobbycity arrived last week, I love those guys! All it cost me was $8 postage.

None too soon, as my little controller stopped working a few days ago!

Now back on 8S2P pack, much more civilised