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rotax Tacho verses digital

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graeme bird

Joined: 15 Jul 2010
Posts: 434

Posted: Tue Nov 13, 2012 11:05 am Post subject: rotax Tacho verses digital

Interesting that compared to my new digital tacho that controls the VP prop, the rotax tacho over-reads by around 150rpm. Id trust the digital rather than the needle but I wondered if anyone else has found the same?



while mentioning needles - my flight sunday took me past a couple.

DSC01045neddles IOW.JPG

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_________________
Graeme Bird
kit4 (Wagstaff) TBD
Kit3 G-CLXU (Gregory) mono 914 xs Woodcomp
Kit2 G-PATS - (kesterton) Mono Classic 912 warpdrive
Kit 1 G-UMPY - Mono Classic/XS 912S, Woodcomp G(@)gdbmk.co.uk

rlborger(at)mac.com
Guest

Posted: Tue Nov 13, 2012 11:18 am Post subject: rotax Tacho verses digital

Graeme,



Beautiful picture!



Blue skies & tailwinds,

Bob Borger

Europa XS Tri, Rotax 914, Airmaster C/S Prop.

Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP

3705 Lynchburg Dr.

Corinth, TX  76208-5331

Cel: 817-992-1117

rlborger(at)mac.com



On Nov 13, 2012, at 1:05 PM, graeme bird <graeme(at)gdbmk.co.uk> wrote:






Interesting that compared to my new digital tacho that controls the VP prop, the rotax tacho over-reads by around 150rpm. Id trust the digital rather than the needle but I wondered if anyone else has found the same?



while mentioning needles - my flight sunday took me past a couple.



--------

Graeme Bird

G-UMPY

Mono Classic/XS FWFD 912ULS/Woodcomp 3000/W

Newby: 35 hours  

g(at)gdbmk.co.uk





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=387771#387771





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http://forums.matronics.com//files/dsc01045neddles_iow_196.jpg

pete(at)lawless.info
Guest

Posted: Tue Nov 13, 2012 11:46 am Post subject: rotax Tacho verses digital

Hi Graeme



Has the Rotax tacho been calibrated?  If not they are often inaccurate. Mine

certainly was.



Regards



Pete

--

frans(at)privatepilots.nl
Guest

Posted: Tue Nov 13, 2012 11:57 am Post subject: rotax Tacho verses digital

On 11/13/2012 08:05 PM, graeme bird wrote:



 	  Quote: 	
		   Interesting that compared to my new digital tacho that controls the

 VP prop, the rotax tacho over-reads by around 150rpm. Id trust the

 digital rather than the needle but I wondered if anyone else has

 found the same?


	


As far as I know it can be somewhat tricky to connect two tacho's at the

same time. It is a weird interface, nor digital nor analogue. You can't

trust either of them. If you really want to know, you'd better check the

rpm against a seperate rev counter on the prop and recalculate this to

engine RPM and see if it matches with any of your gauges.



 	  Quote: 	
		   while mentioning needles - my flight sunday took me past a couple.


	


Very nice! I presume this was in the UK? Is this near land's end?



Frans

Mark Burton

Joined: 10 Jan 2006
Posts: 74

Posted: Tue Nov 13, 2012 1:01 pm Post subject: Re: rotax Tacho verses digital

Hi,



The Rotax tacho really cannot be trusted. Many years ago, one of my customers told me that when he fitted a CSC-1/P constant speed controller, it showed 600 RPM more than the Rotax tacho! So when the customer thought he was using around 5700 RPM on takeoff he had actually been using 6300 every time. Somewhat ironic that installing the CS controller actually reduced his takeoff performance by about 10% (but hopefully prolonged the life of his 912S).



The Rotax tacho has a little pot in it you can twiddle to adjust the displayed RPM but it's impossible to get at when the thing is in situ. Also, if memory serves me right, Rotax decreed that it should be calibrated something like every 50 hours!



Cheers,



Mark

pjeffers(at)talktalk.net
Guest

Posted: Tue Nov 13, 2012 1:33 pm Post subject: rotax Tacho verses digital

My experience would show as with Mark that the Rotax RPM gauges are not to be trusted. My original  was some 200rpm under reading when new. Europa re calibrated it but some 2 years later it had gone way out again.  I rely on the digital readout from my EIS from Grand   Rapids.   

   

Pete Jeffers  

   

--

graeme bird

Joined: 15 Jul 2010
Posts: 434

Posted: Wed Nov 14, 2012 11:53 am Post subject: Re: rotax Tacho verses digital

Thanks for the replies, and compliments on my photo. 



The Needles are at the western end of the Isle of White about halfway along the UK south coast.

One might see them when crossing from Cherbourg.

New compact camera, 20 Mpixels and I am staggered at the difference. I will add a zoom on portsmouth so you can see if interested.

considering its hand held through the perspex.

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graeme bird

Joined: 15 Jul 2010
Posts: 434

Posted: Wed Nov 14, 2012 11:56 am Post subject: Re: rotax Tacho verses digital

sorry cant seem to attach two pics on one post, so here is the original shot

DSC01100portsmouth.JPG

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Fred Klein

Joined: 26 Mar 2012
Posts: 503

Posted: Wed Nov 14, 2012 5:07 pm Post subject: rotax Tacho verses digital

Wow Graham...excellent!



Do I spy the HMS Victory docked in the center of the photo? Takes me back to a memorable visit many years ago...



Fred



do not archive



On Nov 14, 2012, at 11:56 AM, graeme bird wrote:



 	  Quote: 	
		   

 

 sorry cant seem to attach two pics on one post, so here is the original shot

 

 --------

 Graeme Bird

 G-UMPY

 Mono Classic/XS FWFD 912ULS/Woodcomp 3000/W

 Newby: 35 hours  

 g(at)gdbmk.co.uk

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=387925#387925

 

 

 

 

 Attachments: 

 

 http://forums.matronics.com//files/dsc01100portsmouth_427.jpg

Troy Maynor

Joined: 10 Jan 2006
Posts: 162

Posted: Thu Nov 15, 2012 7:03 am Post subject: Re: rotax Tacho verses digital

Yes, Graham, very nice pictures. I'd hate to have to cut the grass along the edge of those needles.   Fred, the pic of Southhampton also takes me back. This was my very last port of call in March of 1984 when the USS Independence pulled into Portsmouth for a few days. I remember well walking past the HMS Victory there. I enjoyed much good times in London, and touring Stratford-on-Avon and Bath and many stops in between. Had the best ale ever in Oxford at the White Stag, I think it was.

Aahh, those were the days my friends. OK, I know. Off subject.

Troy



do not archive

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