Tunnelstuff in Norway

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Geraghty

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I have been bouncing info off of Joao Xavier and I am hoping to fall into the 1.25:1 range but I am finding out that this may not be the case. I had originally thought I would use a timing belt to drive the prop shaft but that may change. A belt drive would mean 2 outboards and gears would mean 2 car engines so I will see what works best.
Carl,
Way back when ...... I built a twin motor mount for [2] K&B .21's......I used a belt drive twin to one common prop shaft......
I used Kevlar belts .....at the time that was the strongest belt available.....
In short the my choice to use belts as a drive mechanism was a nightmare......
I still have that mount to remind me to "never" go down that path again......cogged belts do not understand the rpm......
I would like to add another problem I experienced with the twin belt drive system......
The needles of the [2] motors have to be "perfectly" in sync and the throttle linkage was a nightmare.....
On the test stand maybe one test run out of 10 would have perfectly in sync needles........
Maybe with todays flow meters maybe that would be better.........
I often thought that if I ever tried this again I would use car clutches on the motors to help the motors stay in sync.......
 
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Carl Van Houten

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I have been looking at belt drive trains and wondering if they were have issues with them. Thanks for the advise Rod. I was going to try a timing belt but that sounds like trouble. If I go with gears I will need to bring the engines in closer to the drive shaft to keep the gears from being so large in diameter. Right now the center to center distance is 1.475".

Joern has his really tight and that is what I will have to do as well. I ordered a little 3D printer about a week ago just for prototyping small stuff like this and as soon as it comes in I can make a mock up too. I plan to mount mine on a K&B 7.5cc lower unit. Joern has been doing this kind of stuff for a while now and will have his in the water long before I will have mine. Below is the mount I was working with but I will have to rethink this approach now and go with a tighter center to center grouping that will work better for gears.
TWIN BRACKET v10.png
 
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Geraghty

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There is no doubt in my mind that if anyone can make a twin .21 OB work it will be you younger guys that are more technology oriented...........
My experience has come from a brick and mortar approach to engineering a project.....Most guys my age simply are not programmed that way........lolol
My approach to RC boating development resulted in a thousand skinned knuckles and a bucket of bandaids...lol
There is also no doubt in my mind that you young "whipper snappers" with your computers have the piss n' vinegar to make this work....lolol
In no way am I trying to throw water on your fire.......Good luck to you all.........

After thought......Consider a way to put a mechanically operated buffer system between the [2] motors to make it easier to keep the motors in sync with less sensitive needles ....Like maybe a car type clutch or one way bearings or ?????.......[I am just...thinking out loud here]
I am just remembering what drove me to alcohol and Xanax when I tried this.......lolololol
Memories of this keep floating to the surface.......When I attempted this I ran the twin on 5% and 50% fuel......the result was the needles were a lot less sensitive on the 5% fuel.........
 
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Joern Markset

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After thought......Consider a way to put a mechanically operated buffer system between the [2] motors to make it easier to keep the motors in sync with less sensitive needles ....Like maybe a car type clutch or one way bearings or ?????.......[I am just...thinking out loud here]
I am just remembering what drove me to alcohol and Xanax when I tried this.......lolololol
Memories of this keep floating to the surface.......When I attempted this I ran the twin on 5% and 50% fuel......the result was the needles were a lot less sensitive on the 5% fuel.........
Rod, I believe we have the same thoughts as I have purchased some car clutches and I also got hold of some module 1 clutch bells, means I can use the spurgears that I allready have. Now this will probably take some time as I am only into this stuff in between when I have the time.
It is just very cool to have some challenges, I don`t like easy stuff, it gives me nothing.
About the nitro I am considering prepping all my engines for 16% nitro as that might soon be a reality in Europe. It does not bother me at all, it just demands another way of setting up the engine. (like using a gearbox)
 

Carl Van Houten

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Just started back over and kicked out another model. This bracket has the engines closer to the center like Joern's model. It's the only way to go really. This one will mount straight onto a K&B 7.5cc lower unit and has the same top end bearing that the K&B 7.5cc uses. Just killing some time playing around with it. I may model one like this for a single engine. One thing I noticed is that the mounting holes in the mounting lugs that land on the rear center mounts will cause the bolts to run into each other. An additional mounting hole will have to be drilled into the engine lugs to stagger the bolts. I am going to upload a couple of views of the model and check out of this thread. Good luck with your project guys.

-Carl
Geared Twin v9 4 TOP.png
Geared Twin v9 FRONT.png
Geared Twin v9 ISO.png
 

Joern Markset

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Carl, you are facing the same issues as I did when I started the design. Originally I wanted the engine orientation much more narrow, but I experienced very quickly that it was not possible with the engines that close to the driven shaft. I also needed more material on the mounting lug between the engines. The previously shown gearbox is a testmodel printed in PLA, I found out that I need to do some modifications to it.
I would probably have seen the issues if I took the time to draw an engine that could be assembled to the gearbox inside Fusion, but you know how it is, you want the stuff to come out as soon as possible 😂
I am also curious if a print in carbon reinforced nylon will work.... It should be quite strong, and I think it is worth a try. 🤔
 

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Carl Van Houten

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I extruded all the geometry down into the base plate with no undercuts to provide maximum strength to the upper structure hoping that it would hold up this way since it needed to be put on a diet to avoid an extreme overall weight. With the engines set at 45 degrees the resulting web at the middle lugs is about as thick as it can be without backing the engines away from the center drive gear. It's a bag of compromises but it can be done.

If the CFN printed part does not provide enough strength for you this model can be machined from 7071 aluminum in this configuration. The upper bearing still may be a little small to take the torture from the twins but it is as large as I thought I could go with it without causing problems. I still haven't blown out the center and put the lower bearing in it. If you would PM me your center distance I will adjust this model to suit your setup. Just let me know if I can help you.

The more I dig into this project the more I think the two complete and separate engines is really the only way to go. Dealing with the problems that come from that arrangement is not really that bad but locking the engines together is (as Rod has said) going to fall into the R/C self abuse category for sure. Gears are limited, space is almost non existent tuning and keeping them synchronized is going to be another level of frustration so I am thinking that a single geared setup is all I will be fooling with.

I came, I looked, I tried and I ran LOL 🤪

-Carl
 
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Joern Markset

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Here`s a short clip from testing a new small tunnel setup, still lot of tweeks left but it is getting closer.
Engines is OS T1203 (stock engine) with a M2001SC manifold and a T-1070SC pipe.
Carb is OS 61A
Hull is designed, owned and driven by Andreas Nodland.
 
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Joern Markset

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It’s been a while…. Finally I found some time to knock out a prototype of the twin gearbox.
Have no idea when I will be able to test, but it will happen eventually 😅
Also working on a prototype fronthousing for the CMB 45RS EVO. I’m not in a rush since I have a fearly good number of Novarossi left on the shelf. But sooner or later it will be a reality 🤓
 

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Geraghty

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Here`s a short clip from testing a new small tunnel setup, still lot of tweeks left but it is getting closer.
Engines is OS T1203 (stock engine) with a M2001SC manifold and a T-1070SC pipe.
Carb is OS 61A
Hull is designed, owned and driven by Andreas Nodland.
I like this......🤞🙌
 

John Beardslee

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There is no doubt in my mind that if anyone can make a twin .21 OB work it will be you younger guys that are more technology oriented...........
My experience has come from a brick and mortar approach to engineering a project.....Most guys my age simply are not programmed that way........lolol
My approach to RC boating development resulted in a thousand skinned knuckles and a bucket of bandaids...lol
There is also no doubt in my mind that you young "whipper snappers" with your computers have the piss n' vinegar to make this work....lolol
In no way am I trying to throw water on your fire.......Good luck to you all.........

After thought......Consider a way to put a mechanically operated buffer system between the [2] motors to make it easier to keep the motors in sync with less sensitive needles ....Like maybe a car type clutch or one way bearings or ?????.......[I am just...thinking out loud here]
I am just remembering what drove me to alcohol and Xanax when I tried this.......lolololol
Memories of this keep floating to the surface.......When I attempted this I ran the twin on 5% and 50% fuel......the result was the needles were a lot less sensitive on the 5% fuel.........
Rod, did you give any thoughts to running a common plenum or intake manifold for the carb to sync the engines?
 

Geraghty

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Rod, did you give any thoughts to running a common plenum or intake manifold for the carb to sync the engines?
Yes .....We did that originally with the little twin .21 David Hall and I built........It was a disaster......We chased that SOB for a week before separating the [2] motors making them [2] individual motors with separate induction platforms connected together with a single crank firing at 180 degrees apart..... The minute we did that everything fell into place.....We ran that motor on a test stand several times at a race in Evansville at 44,000 RPM until it ran out of fuel.....That was probably in about 2006/2007......I still have it on a test stand just to look at it...;)
I can still remember that after we fired it up that Ernie La Fleur yelled from the other end of the pits ...."what in the XXXX was that"....lol
At 44K it was literally painful to listen to......
 

John Beardslee

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Yes .....We did that originally with the little twin .21 David Hall and I built........It was a disaster......We chased that SOB for a week before separating the [2] motors making them [2] individual motors with separate induction platforms connected together with a single crank firing at 180 degrees apart..... The minute we did that everything fell into place.....We ran that motor on a test stand several times at a race in Evansville at 44,000 RPM until it ran out of fuel.....That was probably in about 2006/2007......I still have it on a test stand just to look at it...;)
I can still remember that after we fired it up that Ernie La Fleur yelled from the other end of the pits ...."what in the XXXX was that"....lol
At 44K it was literally painful to listen to......
Sounds very familiar, Ron Logghe and I never found the magic to make it work either, the only application that I know of that worked was in the Chrysler power tanks of WWII that my father in law was part of the engineering team that synced the 2 engines. Ron and I thought maybe gearing the engines might be the answer but tried it on a test stand setup but it was obvious at the outset that we were wasting our time.
Jerry Betke was the person that had the answer for John Bridge to keep from blowing gears in his geared twin. “Shaved Crown Gears”
 

Geraghty

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Here`s a short clip from testing a new small tunnel setup, still lot of tweeks left but it is getting closer.
Engines is OS T1203 (stock engine) with a M2001SC manifold and a T-1070SC pipe.
Carb is OS 61A
Hull is designed, owned and driven by Andreas Nodland.
Joern,
Do you have any idea what prop Andreas was running in this video?
I can't tell from the video but I assume Andreas is running a gearbox.....Do you know what is the gear ratio of the gearbox?
Thanks , Rod
 

Wasted wages

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I have been looking at belt drive trains and wondering if they were have issues with them. Thanks for the advise Rod. I was going to try a timing belt but that sounds like trouble.
We had a couple of guys in the club try to belt drive two .67's in mono's for a while... the results were impressively fast, the sound was incredible... if it could finish a heat.
Many broken belts were joined by a broken rod or something just as disasterous. By the time you heard the overrev, it was too late...If we were lucky it would start to peel teeth off the belt and the engine would surge and you could shut it down quick.

Each engine drove a single shaft via its own belt not a single belt driving everything...

I still have a mount setup,,, I'll see if I can find it and get a picture of how it was made.
 

Joern Markset

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Joern,
Do you have any idea what prop Andreas was running in this video?
I can't tell from the video but I assume Andreas is running a gearbox.....Do you know what is the gear ratio of the gearbox?
Thanks , Rod
Rod,
Yes I do. He was running a Prather 215 and gear ratio was 1.81:1
 

Joern Markset

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Interesting, nice when you have 3 D drawing & CNC access.

Kind of the same concept as mine.
Yes, the purpose is exactly the same. However, my prototype does not need any modifications to existing parts. It is a complete frontbox that can be swapped with the original frontbox. Bearing, bushing, clip and flywheel will remain untouched. It also bolts to the original holes on the K&B lower. (threads needs to be drilled out though)
 

jaxracer

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Jan 17, 2005
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I can hardly believe it, but the drawing for a new protoype is done. It is for the 45RS EVO. (M-Line will be different with double bearings)
Very cool, excited to see this once completed. Since it is eliminating the original backplate, this should allow the engine to sit lower than traditional conversion kits correct?
 
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