Big Hit - 20S - Cromotor build

hjns

hjns

100 kW
Joined
Aug 20, 2011
Messages
1,273
Location
Basel, Switzerland
Hi all,

This will be my 3rd ebike, and my second build. The first was a Cheap Chinese Ebike. Forget about it as soon as you can. My second bike was my first build, and it evolved into a Cromotor FS bike. Of course, I will try and incorporate everthing I have learned the past 2 years into this new build.

I just got my hands on this baby: http://www.ebay.de/itm/Specialized-Bighit-FSR-rahmen-kaum-gefahren-neuer-fox-daempfer-24-zoll-/300927052932?_trksid=p2047675.l2557&ssPageName=STRK%3AMEWNX%3AIT&nma=true&si=FA8OrtMXrBvJVQ0RrQgdwOHyDg8%253D&orig_cvip=true&rt=nc

$(KGrHqVHJE!FGvgI)BC7BR0GdzFErw~~60_58.JPG


And I got another Cromotor from HoV. I will lace it into a 24" Halo SAS 36mm rim. Any tire recommendations?

Now, I have two controllers that I am considering. One is a MethTek 24FET 4110. The other is a Zombiess 24FET 4115. I want to go with a flexible setup, that allows swapping the controllers. And swapping batteries as well, either 20S or 30S.

New wire is coming in from the King of Hobby in China:
B8A1650-08.jpg


And the battery box will be a saddle construction, so that I can take it off the bike for easy charging. Combination of carbon fiber and glass fiber composite.
GF-004MQS.jpg

H3K-CAP180.jpg


There will be a CA with temp feedback. I am still looking into a 12V internal fan system to keep the motor cool. Drilling holes in the covers already.
 
Sounds awesome Henk!

Subbed.
 
Another nice piece came in. Used, but still going strong!
DHX 5.0 Coil 9.5"

$T2eC16h,!zQE9s3suFk3BRv2dSCgCQ~~60_1.JPG
 
Nice one :)

I've just bought the same frame, but its already built up.

Running;
Crystalyte TC65
18fet controller
20s lipo

I'm going to use a laptop bag for the packs for now and have something made up like Rodgahs later on.
 
sacko said:
Nice one :)

I've just bought the same frame, but its already built up.

Running;
Crystalyte TC65
18fet controller
20s lipo

I'm going to use a laptop bag for the packs for now and have something made up like Rodgahs later on.
Click to expand...

Cool! Unfortunately, I don't have Timma's skills. Anyway, Rodgahs bike is a big part of the reason why I bought the Big Hit in the first place.
Tell me more about the crown. How quickly does it overheat at 20S >50A?
 
I am hoping the crown 65 on 20s will be like a HT3525 on 24s, but not over heat in anyway.

At 72v I should see 40mph. This is also the Torque version.

I have just finished altering the CAD drawing for the Torque Arms. Rodgah done me a massive favour and sent me the drawings for his.
 
Halo SAS 24inch 36mm rim came in.

XEYv2SJu

cRDgTEdC
 
Have the same frame, also looking to go cromotor.
I have the halo contra 3" tires, would go great with those rims! (although I haven't fitted the yet, so don't know about clearance)
 
Hjns, im keen to see your glass and carbon work. this bike should be a beast. how many amps are you thinking of running?
imo if you can be bothered go more voltage and get that crazy acceleration. (ie 30s as you said)
for 24inch the burm master is prety good for such a heavy motor at 3" wide and has tread coming up the side a bit.
http://www.feltbicycles.com/USA/2013/Shop/Parts/Cruiser/Berm-Master-Tire.aspx
719471-BERM-LRG.png

so its sort of like a dual sport.
 
Rodgahs bike is a big part of the reason why I bought the Big Hit in the first place.
Click to expand...

A couple of guy's mention Rodgahs bike, can some one post a link to that build? It must be kinda cool.
 
Still waiting for parts to come in. Working on the cover to drill holes. Fans have come in, possibly 4 will fit on each side of the stator. With 4 fans of 20cfm, and 4 fans with probably double that, I should be able to create some 240 CFM within the motor, even when it is turning very very slow.

I want to do this as well as possible, so I am taking my time.... sorry.

12V 0.18A Fans 50mm x 15mm 20cfm each
$(KGrHqN,!jkE-oRBvcLgBProOg1psQ~~60_3.JPG


12V 0.36A Fans 75mm x 30mm CFM unknown (given the double current, I would assume double CFM as well; 40cfm?
$T2eC16VHJHQFFhc)ppPBBSB(Sju6qg~~60_57.JPG


Boxxer from Ebay just came in.
$T2eC16N,!ysE9sy0hY3kBR8Pnn3Y!g~~60_12.JPG


It will need some more work, so I ordered new oil rings and wipers from RWC.
boxxer_kit_350.jpg


Strong brakes; Formula RX The One
$(KGrHqNHJB8FHY!w4sheBR9pkBYMLw~~60_12.JPG
 
Teaser, this is where I live (or actually I live in the valley below this castle...)

966784_156581671187660_918955889_o.jpg
 
Looking good. What can you tell us about servicing forks? I have no idea about suspension servicing.

Are you going to mod the frame? If not where is the battery going?

Edit
Btw thanks for posting the cf link on hk. Its quite cheap for sheets and the pre made panels are cool to.
...
Just reread the first post. Can you elaborate on the saddle thing?
 
Awesome work so far Henk!

Subscribed!

Tommy L sends......
mosh.gif
 
pendragon8000 said:
Hjns, im keen to see your glass and carbon work. this bike should be a beast. how many amps are you thinking of running?
imo if you can be bothered go more voltage and get that crazy acceleration. (ie 30s as you said)
for 24inch the burm master is prety good for such a heavy motor at 3" wide and has tread coming up the side a bit.
http://www.feltbicycles.com/USA/2013/Shop/Parts/Cruiser/Berm-Master-Tire.aspx
so its sort of like a dual sport.
Click to expand...

:D
I now seriously considering going 30S2P with my Zombiess 4115 controller "limited" at 100A. Topspeed (not so important to me) would be around 90 kmh. However, torque would start at around 300 Nm from standstill. So that is some serious acceleration. I still hesitate, but limiting to 100A would mean I can still use my 8AWG wire without worrying too much about needing thicker wires.

I came up with these tires:Duro Wildlife Leapard 24" x 3" Tyre
file_1_4.jpg
 
As you can see, I am quite a fan of ducktape.

I used the frame as a mall, covered it with a plastic sheet.
pPEJr7Iz


I then covered the plastic with a rubber sheet. This is very cheap rubber that usually would be between a carpet and the floor to prevent the carpet from moving.
psE3q3l1



I cut the correct size from cardboard, covered the cardboard with glass fiber, covered the part that goes over the top tube of the frame with a layer of carbon fiber / aramide.
Then I outlined the edges of the box with plastic corners from the local DIY shop, and temporarily fixated with ducktape. You can still see the edges of the rubber sheet.
ywNAuQHk


Interim results. I added ducktape around the edges and used ducktape to create curves where there were none. Now I still need to add glass fiber or carbon fiber to cover the ducktape. Unfortunately, the resin does not catch well on the ducktape, so I found that some superglue will keep the glass fiber temporarily in place over the ducktape. Then I cover with resin, and voila. Still need to create the covers, but these will be sawed out of a 4mm board, and covered with a single CF/aramide layer for additional strength. Work in progress, may take another month or two.
oWLmZ50H

0ELkt5hH

pCK389Qs

OXPOMr60
 
Two 210mm Magura rotors came in.
$T2eC16h,!ysE9sy0k0QCBR6(rCdzNg~~60_12.JPG

1fe765c7f5b0d4fd8f0ecea2d97dca638.jpg
 
jansevr said:
...can you explain exactly how you're planning to use/mount the fans?
Click to expand...

:eek: No, not really. This is as much an experiment as it is an assumed improvement. I ordered several size fans just to try out. Anyway, I want to start with the inlet holes drilled in one cover only (brake side), meaning that the fans suck in a LOT of air through these holes. The fans then blow towards the windings, with the outlet holes in the same brake side cover over the windings.

The fans on the gear side are to have the inlet over the holes in the stator, towards the (opposite) cover on the brake side. The fans on the brake side are to have the inlet towards the hubcover. I hope to fixate the fans onto the stator using screws into threaded holes that I will drill into the stator and a security bolt on the other side.

If this does not keep winding temps below 90oC, I will start drilling holes in the gear side cover as well. The idea is that the active fans need less holes, but I will never know for sure until I try it out. The fans will either be driven by a simple on-off switch or a a pwm like this, depending on the noise.... :mrgreen:
 
may i ask how are you going to fit the cromotor into 135mm dropouts? any solution you already thought about?
 
Hi wojtek,

Initially, I had intended to prolong the rear swingarm using steel plates. I have had the plates phrased from 10mm steel, but due to other reasons I have to discontinue this build.

Valuable parts will be up for sale whenever I can make time to dismantle the parts, photograph them, and put them up for sale. This includes the frame, cromotor, and CAv3 and many other parts.
 
You must log in or register to reply here.
Back
Top