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Henseleit 3DNT - Rocket - 3DMP > Measuring Main Drive Belt Tension
 
 
Cookie Bear
Heliman
Location: Wellington, New Zealand

Hi folks
I'm really enjoying putting this 3DNT together. Awesome engineering. But I find it hard to follow some of the explanations, which would benefit from the odd drawing for clarity. F'rinstance, when it says to use the spring-loaded gauge and press sideways on the main drive belt to check the tension, it's important to know exactly where to push, because the results vary widely. I would have thought mid-span would have given the most sensitive reading. But the manual says push level with the front edge of the sideframe. There are three possible locations: the lower front by the engine mount (which makes no sense), the upper front where the cooling shroud bolts on, or a third location near the two elbows into the fuel tank where the belt passes close to, and is supposed to touch a tooth when the gauge is compressed up to the second mark. Can someone please clarify - maybe even a photo? Many thanks. Martyn.
02-01-2004 Over year old.
 
 
duc996bp
Senior Heliman
Location: Preston, UK

I check using your 3rd option. That is how I understand the instructions unless someone would like to correct me.

John
02-01-2004 Over year old.
 
 
G.Man
rrProfessor
Location: Northants, but soon to be Nicosia, Cyprus

I felt another flyers drive belt today on his 3dnt and was surprised just how loose he runs it...

His was sooo smooth tho, I am gonna set mine like his and see how it goes...

(check him out on the IRCHA 2002 dvd)



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02-01-2004 Over year old.
 
 
Cookie Bear
Heliman
Location: Wellington, New Zealand

John
Thanks for this. That was my first reading too, as this is very close to middle of the longest span where deflections would be most easily measured. But with the engine pulled completely forward in the engine mount slots (about double the thickness of all the shims together) the belt touches the side frame by the time the spring gauge reaches the first mark - and it's supposed to go to the second!
Galifrey - this is interesting comment. I feel mine is tight enough (but not flown yet) so maybe others have overtightened theirs.
Hopefully others will comment. Martyn.
02-01-2004 Over year old.
 
 
duc996bp
Senior Heliman
Location: Preston, UK

Cookie Bear

This sounds like a large gap.

Mine is set to 0.5mm, using the gauge it reaches the second mark. The belt is very tight.

I suppose it does not matter what the gap is, as long as it is equal on the left/right sides and the belt tension is correct.

John
02-01-2004 Over year old.
 
 
G.Man
rrProfessor
Location: Northants, but soon to be Nicosia, Cyprus

Martyn

On the new style gear with no teeth, you have to run the belt tighter than the toothed main gear..

Ignore me if yours has no teeth on it



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02-02-2004 Over year old.
 
 
holger
Heliman
Location: Magdeburg, Germany

Hi Martyn,

the gap between engine mounts and frame strongly depends on the gear ratio you use. I am using a 8.3:1 ratio with a OS 91C-spec an there is a gap of exactly 1mm. If your belt is to loose, you will immediatly hear it.

Holger
02-03-2004 Over year old.
 
 
Cookie Bear
Heliman
Location: Wellington, New Zealand

Thanks - I found with 1.2 mm spacers I got just the right amount of belt tension. Any less and the belt slips on climbout. Maybe I got a "Friday" belt with mine. Cookie.
03-15-2004 Over year old.
 
 
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Henseleit 3DNT - Rocket - 3DMP > Measuring Main Drive Belt Tension
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