Throttle routing through firewall

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Throttle routing through firewall

Postby gkremers » Thu Feb 07, 2013 10:49 pm

Does someone have recommendations for the routing of the throttle and carb cables trough the firewall. In my Pulsar there was more room between the FW and carb so the routing could be somewhat of an S pattern and provide slack in the cable. Some Pulsar guys ran the cable straight from the FW to the carb and had all kind of problems with the movement of the engine pulling on the cables.

The only picture I've seen has the cables running straight from the firewall to the carbs. I would like to keep the penetrations through the firewall secure with no room for cable movement. Not sure how I can do that and still allow room for cable movement.

Any pics or comments would be helpful.

Thanks
Gary
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Re: Throttle routing through firewall

Postby stede52 » Thu Feb 07, 2013 11:12 pm

What engine are you running?
Steve D N419LD
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Re: Throttle routing through firewall

Postby jak » Thu Feb 07, 2013 11:17 pm

Gary call me. Jak
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Re: Throttle routing through firewall

Postby gkremers » Thu Feb 07, 2013 11:21 pm

Steve,
912S

Gary
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Re: Throttle routing through firewall

Postby Wes » Fri Feb 08, 2013 10:15 am

Gary,
I had a couple of important design requirements for the throttle cable routing:
- the best firewall fume seal I could get
- minimize the engine motion influence on cable function.

And knowing the sensitivity of carb synchronization to cable configuration, I wanted to provide a routing that didn't tug or push on the carbs.
Having two carbs on an engine that rely on a user supplied cable lashup is not one of Rotax's better ideas!
This is what I ended up with:
DSC05072.JPG


Kinda hard to see in this photo, but I fabricated clamp blocks out of aluminum and drilled appropriately angled holes to restrain the cables.
The white block nearest the coolant bottle are for the throttle cables and the other blocks are for the enrich (choke) cables.
DSC05157.JPG


So far, (28 hrs on the motor) the configuration seems to meet the design objectives.

Hope this helps,
Wes
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Re: Throttle routing through firewall

Postby rmullins » Fri Feb 08, 2013 8:23 pm

I don't like the throttle cable that was supplied with my kit. One of the first steps in the Rotax carb sync is to pull the throttle cable back to it's stop so you don't pull against the carb stops. My cable doesn't have a stop (don't know if current ones do or not). and what limits the cable travel is those wimpy stops that are easily bent, which then gets your carbs out of sync. I try to keep that in mind but sometimes when when squeaking into a tight spot I pull too hard on the throttle "brake" and then I'm needing a carb sync again...
Rick Mullins  #144
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Re: Throttle routing through firewall

Postby JackLeroux » Tue Feb 12, 2013 5:44 am

Gary,

What did Jak have to say? What was your solution for your throttle cable routing?

Thanks,

Jack
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Re: Throttle routing through firewall

Postby gkremers » Sat Feb 23, 2013 5:29 pm

I spoke with Jak at the factory. They run them straight thought the FW to the carbs. There is a relief bend aft of the FW to give the cable room to move with the engine. It is not an air tight seal as the cable passes through the FW. I checked with a friend that has a Kitfox and they route it the same way. My concern of course is fumes, smoke, whatever can pass through the FW to the cabin through any unsealed hole. Looking at how the boot cowl seals up to the FW I guess the space where the
throttle and enricher cable pass through isn't a big deal.

I do like the way Wes did his.

Gary
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Re: Throttle routing through firewall

Postby FredHoffman » Sat Apr 16, 2016 10:56 pm

I thought it would be good to have a solid attach to the firewall and give some leeway for engine vibration too. I installed eyeball firewall fittings for the cables.

Fred
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