Softstart Module

[DocRon]

I have a 2008 CTLS that had a rather nasty starting problem. About 1/3 of the time, especially when the engine was cold, trying to start the engine would end with a Bang. That is, the blades would turn over a time or two and then just stop so suddenly that it would shake the airframe. For a time this happened 2-3 times before the engine would start. I realized that this had to be hard on the engine but didn't know what to do.

 

Then my AI, Mr. Kent Johnson, at Stanton Sport Aviation (in Minnesota, www.stantonairfield.com) suggest the Softstart Module from Bully Hawk (www.bullyhawk.com) for $219.95 + shipping. Kent installed this module on top of the existing ignition (see softstart2 image). He added an additional starter button to the ignition panel (see softstart1 image) because of the new starting procedure.

 

The way this module works (in layman/amateur language) is that the module starts the engine on the number 2 mag initially with the timing retarded for a second or two. Then the timing goes to normal shortly thereafter. This causes the engine to start just as quickly but somehow more gently. The new starting procedure is as follows:

 

1. Push Battery fuse IN.

2. Turn starter key to magneto 2.

3. Press starter button until engine starts.

4. Turn starter key to magnetos 1+2.

 

Sounds funny, works beautifully. The engine starts easily and no more Banging to a stop in the starting sequence.

 

Best of all, Kent wired this module into the ignition system (don't ask me how) so the engine can be started either way: Softstart or Normally. He also called Flight Design for permission and said that a LOA was on the way. It took two hours of labor for the installation.

 

So, if you have this type of starting issues with your engine, consider this additon. I'm very pleased with the result.

[opticsguy]

The new standard ignition modules have soft start (5 seconds) built in, and no extra switch is needed, just turn the key. It's about $900 for the pair, though.

[sandpiper]

$900 for the pair? Did they come down in price? Last I heard it was about $900 each.

[DocRon]

$900?? Wow! Looks like I got off easy for about $400 total.

[Roger Lee]

To take full avanage of the Rotax soft start system you also need to replace the fly wheel as it changes the timing. $750The Rotax modules have an introductory offer and is still being offered by some.

[Runtoeat]

Roger, you say that flywheel has to be changed with the Rotax soft start system??!! Not sure what it costs to remove the engine, replace the flywheel and re-install the engine but the cost of the modules may just a small part of the total cost. Wow. Does one have to change the flywheel with the Bully Hawk system?

[Roger Lee]

The Bullyhawk system does help and it does not need the fly wheel change. Rotax took it a step farther and made it better. Bullyhawk was just an after market add on which works, but Rotax re-designed the system and made it even better. The older Rotax engines start at 4 degrees before top dead center and the new engines with the soft start fire at 3 degrees after top dead center and and adjustment to the ignition module firing. Bullyhawk can't change this and just alters the ignition module firing. Just using the Bullyhawk helps, just using the soft start Rotax modules help, but to take full advantage of the soft start system then you need the Rotax modules and the flywheel.

[DocRon]

The Bullyhawk system does help and it does not need the fly wheel change. Rotax took it a step farther and made it better. Bullyhawk was just an after market add on which works, but Rotax re-designed the system and made it even better. The older Rotax engines start at 4 degrees before top dead center and the new engines with the soft start fire at 3 degrees after top dead center and and adjustment to the ignition module firing. Bullyhawk can't change this and just alters the ignition module firing. Just using the Bullyhawk helps, just using the soft start Rotax modules help, but to take full advantage of the soft start system then you need the Rotax modules and the flywheel.

 

 

That's it, Roger, dash my new-found joy and replace it with abject anxiety

 

It does work without the fly wheel replacement though. I've had no "Bang" starts since it was installed. I'm happy with that.

[opticsguy]

With the new modules I have to change the starting procedure somewhat. Now I crank it once with full choke. It will usually sputter and stop. Then I go to about 1/5 throttle and no choke and it starts instantly, runs rough for 5 seconds, then purrs at 2200 RPM. I found this procedure by trial and error. If there is a better way to use the soft-start with the old flywheel, let me know.

 

I do know that you don't want to add too much throttle during the first 5 seconds, or it will go to 3500-4000 RPM before you can react.

[Runtoeat]

Trial and error shows my choke adds too much fuel at semi-cool temps. In winter, I use full choke. If starting in temps above 50 F, I have an intermediate setting for the choke. Throttle is left closed in both conditions. This procedure provides solid starts for me. I think that my choke was set up for operation in cold temps and this could be adjusted inside the carbsbut my intermediate setting, which I pull the choke lever back about 2/3rds of the full travel, works well for me. If I use full choke at warmer temps, I get a "no start" or a sputtering start that ends with a "no start".

 

A side note: If my starter is held until I am satisfied that the engine has fully started provides positive starts for me. I never get a kickback or any "bangs" during start by doing this. All starts are positive. My understanding is that holding the start key "on" unitl the engine is fully running does no damage since there is a sprag clutch which allows overspeed of the flywheel to the starter.

[Roger Lee]

Hi Dick,

Your right on the starter disengaging. The sprag clutch engages when you turn the key. When the engine passes the speed of the starter the sprag disengages completely and then the starter is out of the loop at that point. Two notes on the starter sprag. 100LL over time will clog the sprag up and the engine will need to be pulled and the back end dis-assembled to completely clean it. There is nothing good to be said for 100LL. Don't turn the prop backwards. Rotax says more than one turn, I try and make it never or no more than 1/4 turn. It will stretch the spring out that holds the sprag system together and will be come non functional after a while.

[Jim Meade]

Rotax is also worried about turning the prop back getting air in the tappets. No personal experience, just passing it on from the SI on oil changes.

 

Here's what RotaxOwners.com says about starters and sprag clutches. I think it needs a little dressing up.

 

"General:

-Sprag clutch - What is it?

The Rotax starter motor is unique as it has no “bendix” or other moving engagement mechanism. The starter connects the sprag clutch to the crankshaft via a freewheel gear. When the starter motor is turned, small oblong rollers in the sprag engage the freewheel gear, forcing the crank to turn. Once the starter is turned off the freewheel gear stops and the oblong rollers retract into the sprag assembly."

 

The sprag clutch is quite interesting. It has three uses, overriding, back stopping and indexing. The Rotax applications are overriding.

 

Look at the pictures in this URL and see how the sprags are shaped. They are not oblong and they don't roll. They look more like a squashed figure 8 that is slightly leaned in one direction. They will grip tightly and instantly in one direction and let the driven gear override in the same direction. So, if the driving gear is doing the work and going as fast (or trying to go faster) than the driven gear, the sprags are engaged. If the driven gear is going faster than the driving gear the outer race simply slides over the sprags and they are not engaged.

 

http://www.gmnbt.com/freewheel_technology.htm

 

Sprag clutches can handle a lot of torque. I have one in each of my farm tractors on the "underdrive". When you go up a steep pull, engage the sprag clutch to get to a lower gear and have the power to go over the hill. Going down the other side, you need to go into direct drive again because if you leave the sprag clutch engaged the tractor will coast or freewheel and not let the engine act as a brake.

 

Sprag clutches were first used in aircraft superchargers in WWII, but now they're used in many applications.

 

 

 

 

 

 

 

 

[opticsguy]

Ergo, then engaging the starter while the engine is at 3000 RPM wouldn't do anything to a Sprag except make a grinding noise?

[Roger Lee]

It isn't like a car. The car has no sprag so it will grind, but theRotax sprag won't engage the starter because the engine is turning faster than the starter and the sprag won't try and engage.

[Runtoeat]

Good discussion on sprag clutches. I designed sprag clutches early in my employment. Upon learning that the Rotax starter incorporated a sprag clutch, I tried holding the start key longer and until the engine was up and running to see if this stopped the occasional "kick back" experience during starting. This procedure did eliminate the "kick backs" and "no starts" being experienced. There were two purposes for my post. One was to see if there were other Rotax owners who might have also eliminated "kick back" by holding the starting key until confirmed running of the engine. The other reason for my post was to pass on my experience using a "partial" setting for my choke in moderate temp (+ 50F) starts with the hope that this may also help others achieve better starting in conditions where use of full choke is not needed and actually might delay or prevent starting.

[Roger Lee]

Hi Dick,

You can still get kick back even if you hold the key. Some dont hold the starter /key long enough and they do get it more often, but once a certain rpm is reached the starter disengages on its own even if you hold the key, but that doesn't always mean the engine has started.

The biggest key to a reliable start especially in cold weather is a good carb sync, a proper idle rpm, a good battery, engine temp before you turn the key and good starting technique.

[Runtoeat]

Hi Roger. Thanks for the info. You mention "good engine temp". I know that a Tanis engine heating setup would really help provide consistent starting during cold weather. It's on the "wish list".