# Verner S9 vs Rotec R-3600

Discussion in 'Supplier / Manufacturer Announcements' started by Radialconversions, Feb 18, 2018.

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1. Feb 18, 2018

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I’ve been asked to copy my post over here from my Facebook page. I hope everyone finds this informative.

So the other week I did an up close inspection of the Verner Scarlet S9 for a customer of mine. He was considering using this engine in his project and wanted me to develop the firewall forward for this engine as an option. After the inspection we decided that the Rotec was the only engine that would be able to meet his requirements. It’s disappointing but I can’t see this engine being a viable alternative. Here are the basics what I found.

Pros:
-The engine is higher displacement
-The ignition system is coil on plug
-The fuel system is an EFI
-The electrical harness is fully developed

Cons:
-Direct drive, lose engine efficiency
-Intake pipes are plastic and located directly across from an exhaust port.
-the distance between the plastic intake pipes and exhaust port is minimal requiring a hard bend in the exhaust pipe. If the pipe cracks the intake will be compromised.
-There is no exhaust system provided.
-Cylinders are a modified Honda cylinder head
-Second spark plug drilled right next to the primary, setting up for potential cracking.
-The oil system is a wet sump design requiring the top of the oil tank be at least 30mm below the engine when the aircraft is in a level attitude. Hard to do on a round airplane.
-The alternator is limited to 200w or 16.67amps. This doesn’t leave much margin for other electrical components on the aircraft since the engine is fully electric and requires a full time high pressure electric fuel pump.
-The alternator is built into the prop hub making maintenance difficult.
-The prop hub is non standard making it hard to use any standard Propellers on the market.
-The prop bolts are non standard, Internal wrenching, non safetying bolts that are roughly half the size of normal prop bolts.
-it’s priced at $31,000 vs$27,500 for the R-3600.
-Lastly, the engine has never flown.

Anyways I hope this report helps, please comment below with any additional questions on my observations.

Last edited: Feb 18, 2018
2. Feb 18, 2018

### BJC

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What does that mean?

Thanks,

BJC

3. Feb 18, 2018

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Good catch, I should have said engine efficiency.

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4. Feb 18, 2018

### Cy V

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I've read about multiple Rotec engine failures. I'm honestly not sure if either engine is all that great.

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5. Feb 18, 2018

### Wanttaja

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Extra "o", I think... "lose torque efficiency," i.e., he claims it has less efficiency in torque.

Ron Wanttaja

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6. Feb 18, 2018

### Swampyankee

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He corrected himself to "engine efficiency," which actually makes some sense. A gearbox would be expected to have about 1% to 2% power loss.

7. Feb 19, 2018

### Propman

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158HP at 2300 rpm on the Verner, no gearbox needed!

8. Feb 19, 2018

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Very true. The engine would be good for an un cowled airplane that didn’t require an electrical system beyond what the engine required. But for anything else it’s a non contender. Also I’d find a replacement for the plastic intake pipes. They kind of went beyond the safety zone in the name of weight savings IMHO.

9. Feb 20, 2018

### Kamilv

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We are a Czech company that has been woking with engines since 1989. Since that time, we have never lowered ourselves to slander or otherwise bad-mouth other engines. We appreciate everyone who knows what they are doing, even if he is a competitor. Unfortunately, for some people this precept is extrinsic and therefore, however unwillingly, I must respond to this defamatory post from the Rotec engine vendor.

The post listed Pros and Cons.
It can be seen that this master who wrote it did not know anything about these engines. Because who writes that having a propeller directly on the crankshaft with a large stroke – therefore with great torque, with the larger diameter of the propeller and therefore with greater efficiency of the whole set - is wrong - so he should rather sell at the vegetable stand.
If the engine is weak, then the reduction drive comes in, and in most cases it is the problem: gear teeth cracking in the gearbox and thus stopping the engine immediately. There is no secret that in Rotec engines this phenomenon also appears. Or was it secret?

Intake pipes:
Yes – they are made of fiberglass – not plastic, where it must be kept at least 1 cm distance from the exhaust. It was created due to the European Union standards for reducing the weight of the engine - ultralight - the take-off weight of the aircraft is 450 kg. Steel pipes can be supplied on request, but after 4 years of operation there have been no problems yet.

Exhaust -
Yes - we are still looking for an exhaust system manufacturer for our customers - so if anyone wants to manufacture them, let us know.

Cylinders
The cylinders are of our own production - aluminum coating + cast iron liner. The head is used from Honda - we never concealed it. It's tested for dozens of years in x units – they definitely do not come off the valve seats, and do not crack like in other radial engines - you know what I'm talking about.

Spark plug
Yes, the second spark plug is drilled, but when using the correct aluminum alloy, there is no risk of cracking - see described master´s experiences with his engines.

Oil
There have been no installation problems to date. The oil level should be below the lower edge of the cylinder head caps so that the oil can flow out by gravity. We do not have scavaging oil pumps because they are the most common source of oil system malfunctions. For example, if the pump intakes air or a pressure loss occurs, the engine will completely flood with oil, and your engine will lock-up and seize. The oil can always flow out via gravity in our engines.

Alternator
Thanks for noticing that. There is an error in specifications. The alternator actually gives a maximum of 1100W at 2400 rpm of alternating current. We supply a regulator that gives 336W-28A. When using another regulator - which we are investigating - it can be increased up to 90A. The customer, however, must assure that this current is consumed in order to avoid overheating.

The alternator is completely maintenance-free - not used from a car like yours.

Propeller hub
It most definitely is SAE 1 standard - so master does not know how to measure. The drive lugs and hole spacing are standard. The M8x1,25 bolts are standard in the EU. For the US, there is no problem changing to 3/8-24 UNF. Other engines shipping to the US already have this.

We're talking to our customers to accomodate everything they need to work with the US standards. If we can develop a different model of engine every year, then changing a thread should probably not be a problem.

Price \$31,000 -
For 5S, 7U and 9S engines, we include free shipping around the world. The problem is that we set and advertise the price in euros, and the USD exchange rate has increased rapidly, which we can not influence. This price was preliminary before the first production and is no longer valid now. For the year 2018 the price is being listed at EUR 22,350.

Flying
Yes – it has not flown yet – it is a new engine. Complete design inside the engine has been well tested in previous versions of our engines. So it should be viable, like our other engines.

And while I am writing in reponse to these claims, perhaps someone can send me or publish a performance chart of the Rotec engines from a test bench! I did not find it anywhere, and it's strange that if I take off the propeller from our 7-cylinder (136 hp) and I put it on an R3600, it turns less rpm. Somewhere there must be a mistake - what do you think about it!

P.S.
Some make motors for looks, we make them for work!

Regards
Kamil Verner – Verner team

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10. Feb 20, 2018

### cheapracer

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Radialconversions, are you or are you not a Rotec agent with a business built completely around the supply and fitment of Rotec Radial engines.

I find your posts biased and somewhat lacking foundation of facts. All you're achieving in the various forums where your "friends have asked you to post" the above, is encouraging other members to post the murky reliability history of Rotec Radials that you work hard at resolving.

Throwing stones, glass houses .......

You should take notes from people like rv6ejguy who not only does not bad mouth his opposition, he actually supports them and is quick to mention their virtues, thus offering Clients confidence in both himself and his industry as a whole.

11. Feb 20, 2018

### Jan Carlsson

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I Think the rotec is a Beautiful Engine, I ones asked them about Horsepower and if they where dyno tested, and questioned the size of propeller they recomended, they told me the Engine was geared (that I know already) and that I didn't understand horse Power, in an aggressiv way. I took my Eyes away from those Engines.

To be able to calculate a propeller for any Engines, it is very important to know the real Power and RPM, aggressiv sale talks don't make the propeller turn faster. if the propeller is calculated for V speed and N rpm with P hp, and it don't live up to that in reality, the Power isn't there.

Jan

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12. Feb 20, 2018

### BJC

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There will be one flying here very soon (replacing the Rotec that suffered a gear failure in flight).

BJC

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13. Feb 20, 2018

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All,

Please look at the threads title. This meant to be a conversation about the differences between the two engine and to take perceptions and put facts to them. I’m very glad Verner has come on to show that I was wrong with some of the perceptions of his engine! Later today I’m going to post the same type of pros cons list for the Rotec and then post the fixes that we are working on for the problems. This isn’t intended to be biased, but a list of what’s different on the two engines.

14. Feb 20, 2018

### Midniteoyl

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Keeping an eye on the thread..

15. Feb 20, 2018

### ScaleBirdsScott

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Both engines have some good design details, and both have potential points of concern that someone who plans to use one or the other to keep them in the air needs to be cognizant of. I'd hesitate to say either engine is unique in these regards though.

Everyone is free to form conclusions based on the available information and their personal requirements. It would be ideal if we had more information across the board. I've got no reason to say one or the other is a poor choice, nor whether one is a particularly great choice for anyone. (Of course I'm not an engine guru qualified to say anything of the sort.) I'd be a little biased but, objectively I can't say either is perfect. Having been close to the Verner engine for over a year now I'm pretty familiar with what's involved in it; there's a few things I'd prefer different, but nothing show-stopping that isn't already been addressed. I would like more experience with the Rotec to make an informed comparison, as we were considering that engine for a long time and so I've got a pretty-good idea of what its about, but still nothing first-hand besides looking it over at Sun-N-Fun and AirVenture.

Speaking of, I'm looking forward to seeing all the round engines at Sun N Fun in just 2 short months!

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16. Feb 20, 2018

### Topaz

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Indeed.

Looking through your website, Radialconversions, it would've been far more appropriate to post this over in the Supplier/Manufacturer Announcements page (where I'm now going to move it), and to identify yourself as an engine dealer who markets Rotec engines exclusively. We don't mind commercial posts here on HBA, so long as they're posted in the correct section of the forum, and any product affiliations by the poster are openly identified.

I completely understand the current trend towards "content marketing", but we don't do the variation of it where "objective" opinions turn out to be a promotional piece. Please keep your affiliation with Rotec out in the open, when posting here on HBA. Other than that, best of luck with your business!

Moderator Note: Moved from Firewall Forward to Supplier/Manufacturer Announcements. Left a one-week expiring redirect in the original location.

Last edited: Feb 20, 2018
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17. Mar 6, 2018

### BJC

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Me too. The plan is to have Samson Mite there with the Verner 9. Photos from a few minutes ago:

BJC

18. Mar 6, 2018

### cluttonfred

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That was very bad form by a Rotec vendor to start this thread off as if it were an objective evaluation rather than an opinion expressed by someone with a clear conflict of interest. Bravo to Verner for the measured, factual response.

19. Mar 7, 2018

### flyinut

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20. Mar 7, 2018

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