View single post by Esprit2
 Posted: 10-15-2016 10:46 pm
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Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 337
qwerty wrote:
Tim are there any specs on the HTD belt (which i was looking for but can't find the crank pulley, otherwise i would have gone down that roadAny of the Lotus parts specialists should be able to provide you with the crank sprocket (JAE, Dave Bean Engineering, SJ Sportscars). Failing that, contact Mike Taylor at Lotusbits in the UK. He can probably set you up with a serviceable used part.
Lotusbits Ltd, (Mike's a good guy, but terrible at answering email)
07866 255 614 Cell, Mike TaylorTim are there any specs on the HTD belt(snip)with regards to Hertz tuning?Lotus issued a frequency spec for the B-prefix, HSN HTD belt. It does NOT apply to the earlier A-Prefix, HCR HTD belt, and definitely not to the trapezoidal belt. The spec changes the basic procedure from tensioning at TDC, to tensioning at 30° BTDC. The correct frequency response is 100-110 Hz.

The belt tension varies quite a lot as the crank is rotated, so crank position is critical when checking the tension. The original tension specs (both J-H & Lotus) call for checking tension at TDC; and the later frequency spec (circa 2000) calls for checking at 30° BTDC. Watch what you're doing, and don't mix them up!!Thanks for the heads up on whine = too loose. I will report back, also with a Hz frequecy.Nope! Read it again... whine = too tight. A belt that whines is too tight, so back off a bit.There are apps for the iPhone out there for frequency tuning (Snip)...I use TuneIt! on a laptop (they have versions for several smart phones as well), with a slender boom mic (stick mic?... Harry Potter's wand). The mic is easier to snake in to the timing belt, while the typical phone is too bulky (more of an issue on a Turbo Esprit... not so much on a J-H).

Most of the frequency apps are musical instrument tuners, and pick up the entire spectrum... meaning a lot of 'noise' outside the 100-110 Hz range. If your app has a 'set-up' option, narrow the band to little more than the target range. Something like 75-135 Hz. That will provide a much cleaner reading.

Tim Engel