SkidMan

My Feedback: (17)

First, thank you to those that helped me ID an engine a week or two ago as a Homelite 25cc. I had never even considered that as a possibility.

This engine is more likely to be what I was told it was, a Quadra 75. I've done some Google'ing and haven't come up with anything definitive. I certainly haven't seen any orange blocks, certainly a prior owner's enhancement.

The motor is on a 1/4 scale L-19 Bird Dog that I am rebuilding which appears to be a Vailly. The original owner really did a very nice job building it some years ago. Some where along the way some weird servo mounts were retrofitted, a damage around the landing grear was poorly repaired, and the most recent owner prior to me stripped a lot of gear from it and did some damage.

The fuel tank that was installed was 16 oz. Since I won't be flying this bird WOT the whole time it might be plenty. What are your thoughts on the fuel tank size. This is a larger engine than I've ever flown so Idon't have a good benchmark.

Thank you for your help.

Paul

SkidMan

My Feedback: (17)

BTW - Ihaven't put a tach on it yet but it seems to spin a 24-12 pretty well.

Antique

My Feedback: (4)

Quadra never painted the cases orange...the engine is a Sachs Dolmar 5.8....the tip off is the non parallel muffler holes and orange case..
It MIGHT be a 5.2 model 133, the 5.8 is model 143...
The angle of the picture looks like the holes are offset, if parallel it's a Sachs 4.2...
The 4.2 will have ZN49 cast on the base of the cylinder, hidden by the case...

SkidMan

My Feedback: (17)

Antique, thank you very much! You got me pointed in the right direction and found this older post by you on the following thread:

http://www.rcuniverse.com/forum/m_10...m.htm#10050077

Since the muffler holes appear to be parallel with the cooling fins in real life I'm exploring your suggestion that might be a 4.2. (See pic)

Found the following post and since it has a has a Walbro carb, but a WJ1D/K2 and not a SDC80 carb, the clue is a little ambiguous.
As near as I can tell the stamp on the cylinder is 49 ZN4W - Supporting that it is a 4.2

The stamp on the top of the cylinder is a 1 over a 2 large "B"and then 2 over a 8 (see pic)

SkidMan

My Feedback: (17)

Also, as distinctly older technology, what currently manufactured engine might compare to the 4.2?

I read threads where it was said to be more powerful than DA-50, DL-50, and G62's.

While the 4.2 is evidently a 69cc engine I would expect the newer engines to be capable of outputing more power for a given displacement than the older engines. The newer engines would certainly have a better power to weight ratio.


Thanks again,
Paul

w8ye

My Feedback: (16)

The Dolmar 70cc chain saws had Tillotson carbs as chain saws. 122 Super, 122SL, & 123

The Walbro WJ-1D was usually on Partner 60-65cc chainsaws

tkg

My Feedback: (1)

The WJ1 is a bit smaller than the SDC, it made less power but was better for sport use.

w8ye

My Feedback: (16)

+1

Truckracer

My Feedback: (19)

Interesting observations. First, even though they were older, the Sachs and most of the Sachs based engines were no wimps by any means. I have not flown the 4.2 Sachs (orange case) conversion, but I have quite a bit of time flying Sachs based engines such as the FPE or Brison 4.2. The 4.2 has quite a bit more power than the G62 and seems to prefer props about 2" larger in diameter. I have flown the G62 in (2) different planes that later had the 62 replaced by a 4.2 .... the 4.2 outperformed the G62 by quite a margin. It is hard to compare these two engines though as the G62 likes to toot ... that is spin up with smaller diameter props where the 4.2 seems to be at its best as a torque producer .... pulling larger diameter, lower pitched props. Its a bit like comparing a tractor to a sports car!

Many threads have been written comparing the G62 to so called more modern engines such as the DA-50 or DLE55. In general the G62 is recognized to be a bit more powerful than the best of this lot. So by default, the 4.2 should be head and shoulders above about any 50 to 55s out there. But then we're comparing engines of considerably different sizes and weights so there are really no direct comparisons.

Most of the Sachs based engines are excellent engines that unless abused should be around a very long time. They will produce power on par with so called modern engines given a real apples to apples comparison. You are correct though, the newer engines will probably be lighter weight.

I still fly a FPE 4.2 and a Taurus 3.2. The 4.2 is a dependable workhorse where the 3.2 is a thoroughbred that I would put up against most any of the newer engines of similar size. Great engines. I have a new plane that I'm powering with a Brison 2.4 so you can see I like the Sachs based engines. Just because they're old doesn't make them bad or outdated!

w8ye

My Feedback: (16)

The Walbro WJ-1D has a 17.46 mm venturi

The Walbro SDC-80 has a 19.05 mm venturi

SkidMan

My Feedback: (17)

Fantastic information for someone who knew nothing about Sachs Dolmar engines other than seeing the name.

I've been doing a lot of Google'ing since Ralph's rapid ID of engine but everyone who has posted on this thread has taught me something important. Thank you!

I'd assume that I could install a SDC-80 carb if for some reason I wanted more power - unlikely in its current plane.

Thank you once again!
Paul

w8ye

My Feedback: (16)

The 3.2 and larger Sachs based engines have a closed port cylinder which tends to give more torque.

The Zenoah G62 is a open port engine which tends to be a engine that likes more rpm.

An open port engine has the intake ports exposed to the cylinder wall from the crankcase to the port outlet above the piston.

Closed port engines have intake ports (transfers) at the bottom of the cylinder with its own outside passage up to the outlet above the piston. Some of these, like the 3.2 have a vented piston (around the wrist pin boss) for the intake charge to come up through the piston and out a little hole in the cylinder wall to an outside passage to loop around and over the piston.

The DL 50 and DLE 55 engines are closed port engines. The DLE 20 & 30 engines are open port.

All the Sachs 2.4 cylinders I've seen are open port.

Generally, gas engines, less that 3 cube are open port.

There are many other factors that enter into torque characteristics besides the port layout such as timing numbers and port area. I consider the DLE 30 to be more of a torque engine than the Syssa 30 and both are open port.

Most of the 2 stroke glow engines, that I know of, were closed port engines though I considered most of them to be RPM engines.

Truckracer

My Feedback: (19)

Good info w8ye!

w8ye

My Feedback: (16)

There are also Kolbenschmidt cylinders on some of the so called Sachs engines. Most of the cylinders were made by Mahle.

You will also see Mahle cyinders on other brands of chain saws like Stihl, Husqvarna, and Dolmar/Makita.

There was another brand of good cylinder that was seen on some Poulan saws and that was Gilardoni.

Antique

My Feedback: (4)

The 5.8 Sachs has a Kolbenschmidt cylineder, the 5.2 is a Mahle...
Gilardoni cylinders are used on the majority of later model Quadra 100 singles and the 200 twin...
Early quadra 100s and 200 used Mahle cylinders, the transer ports are smaller so the Gilardoni cylinders are better.

tms261

I have a Taurus 69. I have never cranked it, but I am finishing a plane for it now. It's cylinder looks a lot like the one in the photograph. Of course its got a different crankcase and is EI. I hope it runs ok. I'm pretty sure these engines have Sachs cyl/pistons, rods and cranks.

I dont think I saw any impressions of how the stated engine ran, other than the 24 X 12 prop. What about vibration? With the double web crank and extra bearing I bet that engine would run forever. Good luck with it.

tms261

I have a Taurus 69. I have never cranked it, but I am finishing a plane for it now. It's cylinder looks a lot like the one in the photograph. Of course its got a different crankcase and is EI. I hope it runs ok. I'm pretty sure these engines have Sachs cyl/pistons, rods and cranks.

I dont think I saw any impressions of how the stated engine ran, other than the 24 X 12 prop. What about vibration? With the double web crank and extra bearing I bet that engine would run forever. Good luck with it.

tkg

My Feedback: (1)

BTW the crankcase is magnesium, so be careful when doing any machining on it. It makes such a pretty blue fire on the lathe bed.

w8ye

My Feedback: (16)

That pretty blue fire is more of a white flash?

Antique

My Feedback: (4)

Friend of mine was taking large cuts of magnesium in a lathe, deflectiing the chips into a container behind the machine...a spark started it on fire...Burned down into the lathe bed...He just packed up his tool box and left...

SkidMan

My Feedback: (17)

So, it sounds like the crank is nicely reinforced. Where is the extra bearing?


The two times I ran the engine it ran very well and without much vibration. I did manage to wack the heck out of my hand on the spring starter. My bad and a lesson well learned.

I just pumped in some of my 30:1 (w/Stihl Ultra), choked and ran it through a couple cycles to prime it, opened up the magnito kill circuit, cranked it maybe 2 or three times with the spring starter and it fired up nicely. Of course, after running a short time it restarted on the first try.



Hmmmmm, magnesium chips and cutting oil?


Paul

Antique

My Feedback: (4)

Original crankcase Sachs based engines have a bearing on the front and another on the rear..Only 3(?) bearing Sachs were the Precision Eagle engines made for Don and Karla Kanak...Their TOC model Precision had a gold anodized crankcase and a $65 FAG double row bearing on the front end...The red anodized P E engines had a single row bearing front and back...
The 4.4 Husky Challenger engines made at the same time by Challenge Tool might have been the same, I suspect Challenge Tool also made the Eagles..Still as good as any engine made, they had a single, inline twin, and inline 3...Never saw a boxer from either company..

goatnick

My Feedback: (11)

I have one of the orange case 4.2 Sachs ,Purchased from B&B.Granger
IN.about 15yrs ago.Was told by Dick that these were cut out of a Sachs
Dolmer chain saws and a fellow in Michigan done the Mods for use in
models,Only drawback was the weight, With B&b muffler andspringStarter
it weighed 6lbs 12 oz,Starts first or second flip and will last a life time,
Good engine,Have mine in a Lanier Staudaucher 96",
Bob