690 Belt Spec's?

[GimpyGolden]

Anyone know the size/spec on the L690 belt? Mine has worn off the text.

Thinking a good option to shorten a 690 to 600-620mm machine is the belt off the new SAB BlackThunder.

It's HTD3 Pitch same as Logo but 642 teeth or 1926mm Pitch Length.
Might be something to look at for guy's popping OWB on 600's.

[beltfedbrowning]

Sdp-si is a good source for belts. Can you use one of these? The website has a great tool for finding belt lengths.
https://sdp-si.com/eStore/CenterDistanceDesigner

642 teeth 1926mm length- http://shop.sdp-si.com/catalog/produ...=A_6R23M642060

652 teeth 1,956mm length- http://shop.sdp-si.com/catalog/produ...=A_6R23M652060

668 teeth, 2,004mm length- http://shop.sdp-si.com/catalog/produ...=A_6R23M668060

[mahbouni]

Originally Posted by GimpyGolden

Anyone know the size/spec on the L690 belt? Mine has worn off the text.

Thinking a good option to shorten a 690 to 600-620mm machine is the belt off the new SAB BlackThunder.

It's HTD3 Pitch same as Logo but 642 teeth or 1926mm Pitch Length.
Might be something to look at for guy's popping OWB on 600's.

The BlackThunder belt is the same as the G630 belt, which is an HTD3 with 1926mm length. It is not as wide as the 690SX belt and I didn't think it would be strong enough for my needs.

I found a company in the UK that can cut custom width belts but the longest they have in HTD3 is 1863mm. This is still slightly longer than the 600SX's 730XL belt, which is 73 inches or 1854mm long. I got them to cut it to 7mm width. The part number they quoted me for is 1863-3M-07 TRANSFLEX ** Ground to width 7mm Wide ** @ £8.91 each

http://www.beltingonline.com/


I intend to try it out some time but it's a back burner project at the minute because I have other things taking priority. I want it for my 600SX to speed up the tail with the 960SX pulleys but before I spend money on 690SX pulleys I'm going to give it a try on my 690SX with a shorter boom. If I like it then I'll order new 690SX pulleys for my 600SX.

[mahbouni]

Now that the good flying weather has migrated to the other side of the world I've finally come back to this little project.

I ordered up a set of 690SX pulleys to try the 1863mm belt I purchased above. I hadn't realized the 690SX front pulley is bigger than the 600SX one and effectively shortened the belt. To use this belt I will need to cut about 10mm off the stock 600SX boom and might not be able to use my Rotortech 640mm blades. It would be fine for 620mm blades though. Some VTX 627's would be perfect.

The next size up would be an 1890mm belt but I was unable to find anywhere that cuts them to custom widths. The next size up from that is 1926mm, the same size as the Goblin Black Thunder, which is only 6mm wide. I eventually managed to find a company in Germany that has Gates HTD 3M 1926mm 9mm belts in stock and can cut them to 7mm width. The custom belt cost me only EUR 11.40, which is cheaper than the standard 9mm belt, and another EUR 9.90 for shipping to the UK. It just arrived today.

http://www.agrolager.de/product_info...ts_id=22007225

I just fitted it in the boom and I think this belt is going to make my 600SX about 25mm longer than stock, which isn't a problem if running >640mm blades. The SAB TB650's will definitely be OK and the Rotortech 670's may even fit. Lengthening the boom will also move the CG further back and I may be able to get away with a bigger motor. Currently using a Pyro 700-56 Comp but I have here a Pyro 750-45 Comp. I didn't try it previously because I knew I wouldn't be able to get the CG right with the stock boom.

[GimpyGolden]

Well it sucks your season is done, I am about there myself.

Cool little side project, but to me it wouldn't be worth the effort cutting booms/tail rods to only end up 25mm shorter than a 690SX boom.

It's too bad the 1863 won't work. Or maybe it will now you know the larger diameter 690 pulley. Should only be 4.5mm shorter than stock (pitch length /2) maybe the tail case move forward this amount and allow it to fit. Feel like giving that a go?

[mahbouni]

Just finished cutting 25mm off the end of 690SX boom. Took me 2 mins. I'm not sure I'd chance a shorter than stock 600SX boom with 640mm blades. I'll have to try it and see how much clearance there is. Just fitting the 1863mm belt inside the stock 600SX boom and around the 690SX pulley I could see I would need to cut about 10-15mm from the boom. I thought I'd try the longer boom first as I can always cut it shorter if I need to but I can't make a shortened boom longer again. Also there's the issue of CG. I'm using 12s 4000mah and can't move any weight further back. A longer boom will give more tail authority and more options for motors and batteries.

I have another 600SX currently with Rail 606mm blades, a Logo 500SE belt and a cut down boom to 500SE length. I never did like the look of the stock 600SX boom with 606mm blades. I could get my fist between the main and tail rotors. So I may end up using the 1863mm belt on this heli with VTX blades when they come out. However I don't have any suitable batteries for it, since my 4000's are too heavy and will set the CG too far forward. If the time comes I will buy some lighter batteries or just retire the heli for spares.

The main reason I want to try the 690SX pulleys is because I want to try a 5:1 tail ratio and improve tail authority at lower head speeds. I tried SAB TB650 blades on my 690SX and the tail is much better than my 600SX but I don't like the big gap between the main and tail rotor.

[smittylube]

What is required to get the 690 tail ratio?
Just the 2 drive pulleys?
I stretched my 600sx to se length and am running medium to lower head speeds. I'm not flying real fast so its been ok, but I just put the rails on and they do WAY better than cyclones at lower HS. so I can go lower now.

[mahbouni]

To get the 5:1 tail ratio you need the 690SX front and rear pulleys, and also the belt tensioner.

http://shop.mikado-heli.de/LOGO-Heli...&c=7574&p=7574

http://shop.mikado-heli.de/LOGO-Heli...&c=8161&p=8161

http://shop.mikado-heli.de/LOGO-Heli...&c=8161&p=8161

However, I might also upgrade to the 690SX OWB and counterbearing support. It seems I need more spacers between the 690SX front pulley and the old OWB hub to make the main gear clear the plastic frames. I added a whole load of them in there but now I can't get the circlip on to the main shaft. Not sure if it's an issue or not, since the 690SX doesn't use a circlip either.

http://shop.mikado-heli.de/LOGO-Heli...&c=7574&p=7574

http://shop.mikado-heli.de/LOGO-Heli...&c=7574&p=7574

[mahbouni]

Originally Posted by smittylube

I stretched my 600sx to se length and am running medium to lower head speeds. I'm not flying real fast so its been ok, but I just put the rails on and they do WAY better than cyclones at lower HS. so I can go lower now.

What I'm finding is my 600SX tail holds great most of the time but when I try some things like a tail down rolling funnel the tail sounds like it's loading up too much and the heli loses composure. I'm sure a lot of it is down to my inability to execute the manoeuvre well but the heli seems to behave much better with more head speed. It just made me think that what I need is more tail rpm but not more head rpm.

I just realized that my 600SX has an older version of the motor mount that binds with the bigger front pulley. Seems Mikado updated the 30mm motor plate. Either I need to get this one or grind my existing one with a Dremel.

http://shop.mikado-heli.de/LOGO-Heli...&c=7574&p=7574

[mahbouni]

Originally Posted by mahbouni

I just realized that my 600SX has an older version of the motor mount that binds with the bigger front pulley. Seems Mikado updated the 30mm motor plate. Either I need to get this one or grind my existing one with a Dremel.

http://shop.mikado-heli.de/LOGO-Heli...&c=7574&p=7574

I don't think I'm going to be able to use my existing motor plate. I would need to grind too much metal from it, which probably compromise it's strength. So I'm going to have to order the latest one.

Just looking at the OWB hub and counterbearing plate in 690SX manual, I don't think I need to order them at all. A circlip wouldn't stop the main shaft from sliding down if the locking ring slips and there's no way the main shaft can slide upwards when the pin locks it to the front pulley. So all I need to do is add my spacers between the front pulley and the OWB hub

[mahbouni]

I replaced the motor mount to make clearance for the larger front pulley, and I also ended up getting the 690SX OWB. My old 600SX OWB was over 5 years old and the main shaft was quite worn so I thought I might as well replace them. I also got the 690SX boom supports to add some extra weight to the back so I can use bigger batteries up front.

Did some test flights today with some SAB TB 650mm mains and Rotortech 105mm tails. There's easily enough clearance for my Rotortech 670mm mains but I didn't test those today. I think I can call this heli my 670SX now.

The tail has much more authority than before and I quickly felt more confident with it. Definitely an improvement. Sounds a lot more healthy too when I really load the tail.

At some point I want to try the 1863mm belt I have and shorten the 600SX boom about 10mm. I'll test it with some Rotortech 620mm mains that I also have.

[goldi80]

mik4081 (730XL LOGO 600) 6,5mm 730/2=365tooth x5.08 =1854.2 from main shaft to tail shaft 850mm
mik4325 (770XL LOGO 600 SE) 770/2=385tooth x5.08 =1955,8 maybe 900mm ???
mik4076 (638XL LOGO 550 SX) 638/2=319tooth x5,08 =1620,5

mik04879 (??????) but it writes on the belt 1980 .
About 2m length 3M belt 7mm wide thickness is 2.5mm very big
from main shaft to tail shaft ???mm

[mahbouni]

Originally Posted by goldi80

mik04879 (??????) but it writes on the belt 1980 .
About 2m length 3M belt 7mm wide thickness is 2.5mm very big
from main shaft to tail shaft ???mm

It's an HTD 3M belt of length 1980mm. It a metric belt and the 3M means the teeth are spaced 3mm apart.

The XL belts are imperial measurement. The 770XL is of length 70.7 inches.