Starter

[Andrew Foster]

Hello all,
our prestolite starter is giving up the ghost.... 61 250 0540
would like to go with a lightwight/high speed replacement. Which unit do you recommend?
skytec or B&C, pros, cons of each? thanks

Andrew
7533P

[Alan Cheak]

Andrew:

Had the same problem several years and I flew my '63/250 out to WEBCO to have the entire starting system checked out. After figuring out that once again my new magnaflux starter was bad, Bob talked me into a B&C starter. I've never had a problem since. Others on this forum will say they love there SkyTec's. I have read a few times of people complaining that every once in a while there SkyTec would give them a problem. Never have I read or heard of a problem with a B&C starter. In fact I love my starter so much, that when I do my engine I intend to keep my B&C and put it on the new engine or keep it as a spare.

Alan

[N3322G]

Andrew,

I'm a sky-tec fan. Have them on both engines. Nice to have two good options isn't it?

[Andrew Foster]

Alan,

Had the same issues with the mangnafux, been leaning towards the b&c. Do you know if any modifications are needed? Or is it plug and play

Thanks
Andrew

[Matt Bogard]

Put on a Skytec just in the last month. Along with the Bogert copper battery cables it throws the prop so fast you can almost taxi on the starter alone!

[Zach Grant L1011jock]

Skytec NL will bolt up with no mods to the forward baffle or power cable length. It is not as light as the really light weight starters, but it still saves almost 10 lbs.
-Zach

[Matt Bogard]

We did have to find about 1.4" in battery cable length. My Bogert copper cable was run nearly perfectly for the old starter so we had to adjust a few Adel clamps holding it but it worked fine. From what I remember on the weight and balance it's only about 5 pounds lighter than the old one but the performance was my main reason for doing it.

[Alan Cheak]

Andrew:

I do know that the SkyTec starter is a true bolt on replacement. As for the B&C I do recall that Bob and the boys from WEBCO had to use a metal grinder on some part of either the airframe or engine casing. I was to scared to look so I just walked around the shop looking at other Comanches. However, I was comfortable in knowing that they knew what they were doing. A simple phone call to WEBCO could answer any questions. Again, I love my B&C so much I'm taking it with me when I replace the engine. A B&C starter, or SkyTec coupled with a Concorde battery is a combination that cannot be beat.

Alan

[Don Nelson]

Hi Andrew,
I installed a B&C starter on my (then) 250 about 10 years ago, partially because of wanting to support them, who had been supporting ICS with Flyer advertising, but also due to having good reports on theirs.
At the same time I found I could shorten my Bogert copper cable a foot by moving it from behind and up the left engine side, over to the right and across the engine lower front.

I ran into one effect of the B&C installation tho, in later installation of a 3-Blade McCaulley prop. Turned out the control cable to the governor hardware was not compatible in its attachment to the B&C starter.
The fix was to use Mooney bell crank hardware, and run the control cable over top of the engine left side cylinders - which I ended up liking better anyway.

Having said all that, I so far find no fault with the Sky Tec starters my (now, 2 yrs) Miller Twin has.

So, as the saying goes, "you pays your money, and takes your choice".
Of course after weighing all the info! (-:'

Best regards, Don

[N3322G]

Don makes a good point on supporting ICS advertisers. I checked before I posted, both Sky-Tec and B&C support the fleet with ICS ads.

[Andrew Foster]

Started doing the install on saturday. Had to remove the left forward baffling, oil cooler, and alternator to get to the starter bolts. The new B&C bolts up a bit easier than the stock prestolite. Easier to get the nuts started. The outer casing of the B&C does hit the oil coller/ propcontroll bracket. A minor modification and easy as it was off the engine anyway. We also had to shorten a bracket that runs from the starter to the alternator, Again a very easy task. I talked to Lamar about soilenoids. They gave me a great troubleshhot technique for soiloinds health. During cranking connect one lead of your volt meter to one side of the soilnoid, and one lead to the other side. It is obvioulsy not +/- specific. Your volt meter will now read any voltage drop during operation. If the drop is great than .2 volts the soilonoid needs replacing. Going to finsih up on Sat and will post the results.

Andrew
61 250

[Andrew Foster]

Finished the install yesterday. In all two solid 8 hour days. I found when bolting the oil cooler up it too hit the casing on the starter. The solution was to move the oil cooler about 1/4 " to the left side by redrilling the holes in the oil cooler flange. That way the bracket for the prop controll cable still is in line. I cleaned up all the conections with sandpaper. Also cleaned the ground stap conections as well. We replaced the starter soiloind. I should mention we do have the bogart cables. It now spins very fast. Mission accomplished.
I do have one question. Thier is a diode wire from the switch side of the soilonoid to ground. Does anyone know the function of this?
Thanks
Andrew

[Hank Spellman]

The short answer is that it helps prevent arcing at the face of the solenoid.

The long answer is not so simple, (although this explanation is simplified). The starter motor is a very large inductive load. Inductors have the characteristic of allowing direct current to pass with minimum obstruction but to obstruct the passage of alternating current, with the obstruction increasing as the frequency increases. What is actually happening when the starter solenoid first connects is the the battery sees a short circuit and delivers a huge current (typically 5 times or more than the running current) until the magnetic fields in the motor build. This all happens so fast that mechanical meters can't react fast enough it really show it. The motor sees the leading edge of the current as the first part of a cycle of alternating current with a very high frequency, even though it is really direct current. However, this part of the scenario is not the problem.

The real problem comes when the starter solenoid disconnects and the current stops abruptly. The magnet fields in the starter are at full strength and contain a large amount of energy. Then the current stops, the fields start to collapse, but the energy has nowhere to go. Also, the collapsing magnetic field causes the voltage in the windings motor to go really high. The path of least resistance is through the barely open contacts of the solenoid, so the energy jumps that gap in the form of an arc which is hot enough to melt the surface of the contacts and leave pits and spikes on the surface of the contacts. Eventually, the surface will become rough enough that the inrush current will weld the contacts together so the the starter motor runs continuously until it is hot enough to burn or melt, leading at all sorts of unpleasantness and expense.

The diode gives the energy of the collapsing magnetic field somewhere to go besides back through the solenoid contacts.

Hank
Henry A. Spellman
(an electrical engineer in another life)

[N3322G]

Hank - by golly, you are an EE AND have a great sense of humor - didn't know that could happen. Just teasing. Apologies for thread creep but couldn't resist after that superb description.

Seriously, nice to have a person with such skills share them with others. Thanks.

[Andrew Foster]

Hank,
Thanks so much for the useful information . I'll leave as is. Is their a way to test to see if the diode is working ?

Andrew