qrf mods

Aahh... The pin is secured by two set screws from below, you can see them if turn the bike upside down.
Open those screws and the pin can be pressed out with a long M3 screw for example.

Hey, someone's been lurking around, lol.
Been a bit busy since I'm on holiday...

Yup, it's 4mm music (piano?) wire and welded to the plates. I stole the idea from someone here, made my own drawings and a friend of mine did the welding.

Had to order four drive shafts from ehirobo.com (just in case), but since I was in a hurry to get the bike rolling, I made few of my own:



plus made a prototype chain guide/tensioner,


Went for a test ride, hit a rock and broke one steering link.
There's a short video from the incident at my pic site, http://janezki.pic.fi/kuvat/RC_stuff/qrf400/
Got the steering link fixed today, mainly because it's been raining all day. It prolly rains tomorrow too, so dunno if I can test the slider throughly yet.

Also, changed the stock 10t pinion to 14t and have a 3000kv L sized motor coming from HK.
It should be just about perfet fit between the frame plates - well see...

That's not normally the place to drive the bike, just wanted to see how it goes there. Won't go back...
This bike's really for sporting fields, parks & asphalt.

Didn't plan any battery upgrade, but pinions (12t & 14t) came from impaktrc.com and are made by Robinson Racing. Also for the stock motor you need a bore reducer, since mod1 pinions are normally meant for 5mm shaft.
Robinson Racing part numbers: RRP1200, RRP1212 & RRP1214.
The motor is HobbyKing's KD36-60-08L 3000kv and if my measures are correct, it really is tight fit between the frameplates.

With stock setup & 3S lipo the bike goes 20.92 mph (33.6 km/h) and 14t pinion gives top speed of 29.28 mph (47.04 km/h). These are just calculated theoretical (=optimal) top speeds.
I'm not looking for anything extreme, just a bit more top end. With 3000kv L motor & 12t pinion I should (or maybe could) hit 35.86 mph (57.6 km/h), which is more than enough for this bike. Going straight is not the problem, turning is...

All calculations made at R/C Calculations.

Here's the "all stock" data for QRF (with 3S LiPo):

Differential Ratio: 1
Transmission Ratio: 3.555556
Other Ratio: 1
Spur Tooth Count: 58
Pinion Tooth Count: 10
Total Voltage: 11.1
Motor KV: 2100
Tire Diameter (inches): 5.82
Tire Ballooning (inches): 0.2
Motor Current Draw: 60
Motor Coil Resistance: 0
Spur/Pinion Ratio: 5.8 : 1
Total Ratio: 20.62222 : 1
Tire Circumference (inches): 19.54 inches (496.33 mm)
Rollout: 0.95:1
Total Motor Speed: 23310 RPM
Vehicle Speed: 20.92 mph (33.6 km/h)
Effective KV Value: 2100
KT constant: 0.64 oz-in/A
Motor Torque: 0.2 ft-lbs
Final Torque: 4.15 ft-lbs
Final Power: 666 watts (0.9 HP)

Note!
Use nominal battery voltages to get accurate results, i.e. 1 LiPo cell = 3.7V

Edited by Janezki - 13/Jun/2010 at 4:32pm

Hi guys, here I show you some mods/add-ons I made and tested successfully.

1) Chain tensioner:


It works well, but makes an awful noise... I got used to it and I'm happy with this version I made (it's version 3) :)

2) Tail protector holder made of wheel stoppers (4 mm). They are connected with a threaded rod. There I insert a protector made from 3mm piano wire (not shown). This works very well.


And yes, it's a dirt bike...

Thank you.
Yes, it's easy to maintain, the spare parts are cheap and it's as simple as possible to build.
Another pro is that you can change the length of the protector if you think you need to. Just open the set screws, set the wire correctly (or replace with different length) and close the screws. Piece of cake...