Santos Dumont No. 18 Hydroplane 1907 by Greg Davis - Scale 1:16

[Greg Davis]

On 4/10/2025 at 3:03 AM, iMustBeCrazy said:

So I'm guessing 2:1.

 

 

These photos are not to scale so don't read anything else in the numbers.

 

Greg, note the clearance between the prop and the hull in the last shot when considering the diameter.

 

 

Craig -

 

I really appreciate you taking the time to (re)check the blade to shaft ratio and I'm glad we came to a similar conclusion!

 

I had been taking note of the prop/hull clearance both in pictures and in the previously mentioned video. It looks like there wasn't a good deal of space! I also had kept an eye on the approximate location where the blade tip intersects the diagonal brace from the engine pylon to the nacelles. The prop / hull clearance was the main reason that I though the first propeller mock-up didn't look convincing enough.

 

Today I put together propeller mock-up No 3 (starting to use the SD numbering system, but don't want to make it to No 18 here!). This one is built to the 2:1 ratio and is scaled to match a propeller with a 2.25 meter diameter.

This one looks pretty good to me currently. The blade shape still needs some refinement as it blends into the shaft - the transition seems a little abrupt right now. 

 

I think that some metal is coming out next. 

 

Also, I've made a decision to have the front of the engine as similar to how it sits in his workshop in this photo:

The mechanics associated with the water pump up front is the same as in this photo:

But not as it had been in the No17 nor when the engine was being installed on the No18:

In the later (final?) set-up, it appears that the water pump is run off a belt drive from a larger pulley mounted to the propeller shaft. This arrangement wasn't present when the engine was being installed.

 

 

 

 

 

[iMustBeCrazy]

A quick upscale:

 

[iMustBeCrazy]

On 4/12/2025 at 6:39 AM, Greg Davis said:

In the later (final?) set-up, it appears that the water pump is run off a belt drive from a larger pulley mounted to the propeller shaft.

I've been trying to nut out what's going on up front, and failed.

Having the water pump aft was normal on the V8 and having the magneto aft helps keep it out of the spray. But what ? and ?? are I have no idea.

There's not much space for ? to be a pulley and ?? could be gear driven so why would you need a pulley?????

 

[Greg Davis]

15 hours ago, iMustBeCrazy said:

I've been trying to nut out what's going on up front, and failed.

Craig - I feel you!

 

Toward the end of February I spent a lot of time trying to better understand the fueling and coolant systems. I ended up having a lengthy and informative e-mail exchange with William Pearce (Old Machine Press and author of that nice paper on Antoinette engines). Here's how it went:

 

On 2/19/2025 4:31 PM, Davis, Gregory wrote:

William –

 

With much thanks to you, I am making progress on the engine. Here’s what it looks like now.

 

I’ve also made a brass fuel tank to add to the model.

 

In the pictures of the No18 Hydroplane, there are two tubes / pipes that leave the fuel tank vertically, then bend over 180 degrees and go back down to the engine. Do you know the purpose of the tubes (pressurization?); but more importantly, do you have a feel for were they attach to the rest of the engine? I can’t decipher this information from the pictures I have of the boat.

 

 

There is a picture of what is believed to be the same engine (when installed in the Santos-Dumont No 17 airplane). There are two pipes that come down in the same area, but to me, they look to connect to the coolant system and are perhaps unrelated to how the engine is set up for the hydroplane(?).

 

 

If you can provide me with any guidance, I would truly appreciate it!

 

Again, thank you very much as your help has been so instrumental to me,

 

All the best,

 

Greg

 

_____

Hello Greg,

Those parts look great. Amazing attention to detail.

I've been staring at these photos for an hour, and I can't figure it out. They kind of do look like they connect to the cooling system, even on the hydroplane. Let's go down that road a bit...  Maybe the tank is a coolant reservoir. The lines could be the coolant return lines pouring the coolant back into the reservoir. The middle two passages would then be the coolant lines taking the coolant into the cylinder Vee and to the front of the engine. The line then Ys into the two radiators. The outlet of the two radiators then Y back into a single line atop the central float. Coolant is then pumped back into a manifold at the base of each cylinder bank. The coolant flows up through the cylinders and into another manifold on each bank. The outlet of these manifolds pour the coolant back into the reservoir. Maybe it would work, but I don't really like it. However, I always thought the tank was a touch on the small size for a fuel tank feeding a V-16 engine. But then, where is the fuel? In the body? In the black tank that we discussed before?

I just don't know. I wish we had some better images of the top of the engine. For what it is worth, it does look like the same engine and propeller in No. 17.

I'll continue to think about this to see if there is a more logical answer. Again, fantastic work!

Best regards,

William

_______

 

On 2/20/2025 1:44 PM, Davis, Gregory wrote:

William –

 

Is there any chance that the conical tank is subdivided with fuel in the back and coolant in the front? I think that there probably is still enough volume in the rear cone to fuel the engine for 2 kilometers and a turnabout.

 

Greg

 

_______________

 

 

Hey Greg,

From the beginning, I always felt it was a fuel tank. I saw the downspouts with petcocks seemingly flowing to the carbs. Yesterday I thought about it being a split tank. The mounting band is probably covering any evidence of a seam, if there were one. The top certinally seems to have one "opening" with the coolant-looking tubes and another "opening" further aft. If the font was coolant and the rear fuel, it would make a lot of sense and also match up with some other (malformed) ideas that I have. Like, why have two downspouts for the fuel just a few inches apart? Surely a Y-pipe would have be far more simple and cheaper to create. Nether of the two downspouts are in the ideal location for a single-section tank, but they are in the ideal locations if the tank had two sections.

Taking a different perspective... What purpose could the tall forward structure serve if the tank were just for fuel? I cannot think of one. Why is there another vent looking thing sightly to the rear? To me it looks like a cap with a vent. I'm not sure you really need that if it is just water in the tank, as I doubt the forward opening with its two pipes is perfectly sealed. I'm kind of leaning to the two-section tank theory. It is the best-fitting "shoe." Exclude the impossible, and what is left, however improbable, must be the truth. But it seems on the small side to me.



William

 

___________

On 2/21/2025 4:25 PM, Davis, Gregory wrote:

William –

 

I like the idea of the 2-part tank and am willing to go with it until I come upon evidence to discount the possibility.

 

So now I am trying to understand how the coolant circulation would work. Based on what you have told me and/or written about the Antoinette engines, I do understand that there is a coolant pump under the engine, that the coolant enters the jackets from the lower outside and leaves on the upper inside of the jackets. From the SD No17 setup, there is a connection from the top of the outlet piping to the tubes that go back up, over, and then into the coolant tank. I can also see that at the bottom of the radiators there is a saddle connection.

 

There are 3 basic questions I have in terms of how the whole system connects. Once again, I am hoping that your expertise can provide guidance!

 

1. Where does the funnel under the tank connect?  I don’t see a direct path to the coolant pump under the engine.
2. Is there a pair of pipes that leave the coolant returns that lead to the radiators – this would make sense to me – and is the coolant pumped into the radiators or is the flow passive?
3. Is there a path for coolant to go from the lower radiator saddle connection back to the input pump? I am assuming the coolant system is closed, but maybe it is not – just carrying the amount needed for a run and the radiators are used so hot / scalding coolant doesn't spray out uncontrollably!

 

 

I thought all of this would be obvious, but the answers are not coming to me presently.

 

 

Also, currently, I believe the black box on the main pontoon is associated with pressurizing the pontoon and nacelles as there is flexible tubing leading to all three of these structures. Also, I don’t see any connections to the coolant system. I do remain curious on how that system works, but not as much so as how the coolant system ties together!

 

Greg

 

_____

Hello Greg,

So glad you asked that question because I have already thought out how I think it works. Of course, I may be completely wrong, but it seems to fit.

Coolant flows down from the forward downspout of the reservoir. It is then carried to the front of the engine where it Ys into the radiators.


The Y inlet to the radiators just above the propeller


It then flows through the radiators and Ys back into a single line atop the main float. The coolant then flows up a pipe (or maybe pipes) at the rear of the engine to the water pump.


Each of the water pumps two outlets feed coolant to a pipe that runs under the engine and connects to a manifold that connects to the bottom of each cylinder in a bank. Coolant flows up through each cylinder’s water jackets and exits the top of the cylinder where it is collected by another manifold for each bank in the Vee of the engine. The single exit of this manifold delivers coolant back up into the reservoir via the tall vertical tubes.


Gravity would allow the coolant to flow from the tank and through the radiators. Siphonic action may even help push the water back up to to the pump, but the pump is what is really pushing the water though the engine and up to the tank.

Again, I may be completely wrong. But, this fits given what is visible in the photos and eliminates some of the questions that we are left with if it is just a fuel tank.


Best regards,

William
 

[Greg Davis]

Continuing on the subject!

 

Here is a picture of the Francois Durant model that had been prepared for the 2009 Santos Dumont exhibition at Museu da Casa Brasileria (the only other model of the SD No 18 that I am aware of). While there are many omissions / questionable representations on this model, it does appear that he had concluded that there was a belt driven water pump up front.

Today, while looking at the photo you last attached, it actually appears that there may be two belts / pulleys - one vertical that would operate the water pump, and one off to the right (in the picture) with another (unknown) function:

The number of accessories on this engine is crazy! As I mentioned in an earlier post, I will be making numerous simplifications as currently I don't have access to information that would allow for more - or even make educated guess on more. 

 

Best I can hope for is to not horribly misrepresent the hydroplane and to hope that other modelers find the subject interesting enough to do a better job in the future.

[iMustBeCrazy]

17 minutes ago, Greg Davis said:

Do you know the purpose of the tubes

Greg, The Demoiselle had a coolant header tank there so I suspect that's it.

 

So, from the header tank through the radiators to the water pump through the lower manifold through the cylinder jackets to the upper manifold and back to the header tank.

Demoiselle below.

 

 

[iMustBeCrazy]

11 minutes ago, Greg Davis said:

Today, while looking at the photo you last attached, it actually appears that there may be two belts / pulleys - one vertical that would operate the water pump, and one off to the right (in the picture) with another (unknown) function:

 

The red arrow is pointing to the camshaft drive gear, note that the pipes to the radiator join behind it and go up then bend back to run along the top of the block.

[Keith Black]

 You guys are way ahead of me on the engines technical details but have either of you considered  a simple thermosiphon cooling system? The elongated radiators on either side appear to be ideal for such a system. 

[Greg Davis]

8 minutes ago, iMustBeCrazy said:

The red arrow is pointing to the camshaft drive gear, note that the pipes to the radiator join behind it and go up then bend back to run along the top of the block.

It should be clear by now that I am not an engine mechanic! Getting around 1970's - 80's racing bicycles was the max for me.

 

Is it possible that this is the end of one of the pipes and it is currently unattached. The lighter colored object could be the second cylinder in?

 

 

But here is another hypothesis:

 

There a pinion gear at 2. The disk behind the propeller has a gear in the back and runs a belt in front. The belt in front go to pulley 3 a double pulley that also has a belt that goes back to pulley 1 and drives the pump.

 

What is curious to me  is what appears to be a flip in the gear ratio between the prop and the crankshaft between when it was on the No17 and when it was finished on No18. The setup in the picture you have above would spin the prop much faster than after it was modified. It also seems that the original setup would be more burdensome on the engine as it probably requires a lot of torque to turn the propeller.

 

[Greg Davis]

5 minutes ago, Keith Black said:

thermosiphon cooling system

Keith - This is a new concept to me! Something more to learn about.

 

Greg

[iMustBeCrazy]

Ok, I think this nails the water pump.

 

The "I don't know" may be a booster pump given the extent of the plumbing and the height of the header tank. Maybe.

The ?? (post 215) may be a gear driven oil pump moved to the front. Just a guess.

The top pipe from the radiator 'Y" manifold could go to the water pump or the lower cylinder manifolds. In the top pic it looks like the water pump feeds the lower cylinder manifolds.

 

EDIT: Sounds like I mostly agree with William.

 

Edited 15 hours ago by iMustBeCrazy

[Keith Black]

 I assume this beast had a camshaft, is the large gear driven off the prop shat the timing gear driving the camshaft? 

[iMustBeCrazy]

3 minutes ago, Keith Black said:

is the large gear driven off the prop shat the timing gear driving the camshaft? 

Yes.

[Greg Davis]

1 hour ago, iMustBeCrazy said:

The 'I don't know' and "Pipe end should go to bottom of radiator' are exhaust pipes!

 

Craig -

 

thanks again for helping me understand this machine

 

Greg

[Keith Black]

59 minutes ago, iMustBeCrazy said:

Yes

 I'm amazed they got away with no oil on those gears unless there was runout oil from/off the crankshaft/prop shaft. Or is there a cover I've somehow missed? 

[iMustBeCrazy]

28 minutes ago, Greg Davis said:

are exhaust pipes!

Doh!

[Greg Davis]

14 hours ago, iMustBeCrazy said:

Yes.

I don't understand the gearing by the propeller. I believe the engine was a 2-stroke, so the gearing between the drive shaft and the cam shaft should be 1:1. Is the camshaft driven in the rear with a gear between the magneto and the engine? The gearing in the front of the No17 setup looks closer to 3:1 and then maybe reversed to 1:3 later.