[One of Many]

Oh, that's right, the screw is a stop on the barrel rotation. These do not close all the way, so in effect they do bleed air. The low throttle needle keeps it from downing on idle. These also meter during the rotation to full throttle.

I think the barrel moves in two directions as it rotates? At least it looked like a typical newer OS style. Maybe that is just on my 4 strokes. It has been a while since I messed with them.

I had heard sand would work as long as it does not drain out of the bend area. I have always thought the increase in volume made the sand loose and it still collapsed on me.

DC

[jwstolk]

....... You just tape the ends and fill the tube with sand .........

i would squeeze the ends in a vice, because with small tubing even a very
small volume change could cause a nice kink... then cut off the squeezed end.
(tape might work ok if the bend is far from the end of the tube ?)
jaap.

[itsme]

Hi there,

I haven't got round to the exhaust yet, so I'll probably try the sand trick tomorrow.

Today I sorted out the mounting bolts, as well as the carb and exhasust mounting screws. I also genearally cleaned the parts up a bit and roughly assembled everything (including the seals this time) with some castor oil. I haven't tightened the bolts up properly yet, but when I turn it over, it is making some nice 'slurping' sounds. It sounds quite promising. There is only one tight spot when everything is assembled that I need to work on - shouldn't be too much trouble.

If I can carry on at the current work rate, the engine MIGHT be ready for the first start attempts on Saturday or Sunday. There is very little left for me to do now. One problem that I am having is trying to find a 0.9mm allen key. The screws that hold the spur gear in place are 2mm grub screws and they need this ridiculously small key. I'm sure I had one somewhere, but where???

I think I'm going to knurl the prop driver now.

Regards
Warren

[itsme]

Hi there,

I thought I would give you the latest update on the engine. I finished the last parts this morning, assembled the engine and got everything ready for the first start atempts. It had reasonable compression, but not as good as my OS wankel.

Late this afternoon I attempted to start the engine. I primed it and gave it a good spin with the electric starter. There was nothing. Eventually after playing with the carb for while, I managed to get it to fire, but it still wouldn't run. I carried on like this for a while, but I soon noticed that it wouldn't fire anymore and the compression had just about completely disappeared. I decided to open it up to see which part had disintegrated/worn away/smashed etc etc, but to my surprise it was just one of the apex seals that had got stuck in its slot and therefore wasn't properly in contact with the housing (this means no compresison on 2 out of 3 rotor flanks). I made the seals a slightly tight fit in their slots thinking that they would wear in, but clearly my thinking was wrong. I opened up the slots slightly and now the seals are a nice, smooth fit. After reassembling the engine, I was a bit shocked, because the compression was all of a sudden A LOT better. It is just about comparable to the OS now. I haven't tried starting it again, as it is too late now, but I will have a go first thing in the morning. One of the difficult things about an engine like this is trying to set the carb up properly - it takes time and can be VERY frustrating.

Mark, I know you have mentioned before that this would be a messy engine. Well, you were 100% correct. Just from my few attempts at starting it, my left arm was covered in oil and I've got a feeling that there is going to be a big patch of dead lawn. My mom won't be impressed, but it's for a good cause...

We'll see if I have a working wankel or not tomorrow...

Regards
Warren

[jwstolk]

I'm very impressed. it looks great, and i hope it runs well.

was the exhasust bending very difficult ?

[CJL5585]

Warren:

I really did like your description of the trials you faced today in the attempt to start the engine. I am sure you will have better luck tomorrow.

I really loved the photo of the prop on the wankel engine. It looks like it belongs there. Just keep your fingers out of the prop and everything will be OK.

It is looking great.
Jerry

[itsme]

Hi there,

I managed to get a reasonably good exhaust bend, but still not as good as I had hoped for. I used the sand and crimped the ends of the tube in the vise. I also made it quite a lot longer than I needed so that I could squash the ends up a bit to make sure the sand was well compressed. The bend I got was OK, but still not as tight as I would have liked. I might make a new exhaust sometime.

Regards
Warren

[LongRat]

Great job Warren, amazing fast progress! Can't wait to hear if it runs well!

[itsme]

Hi there,

I had a few more start attempts today and it was much closer to running, but still hasn't run properly. I am having a lot of trouble with the apex seal springs. After one of its rebuilds, I tried to start it and had it running under its own power for about 2-3 secs. After this, the compression had almost disappeared again, so I opened it up. It looked like one of the seals had got stuck in again, but on closer inspection, the spring had broken in half. I have now broken 2 springs on the same seal - fortunately the pieces didn't find their way into the engine.

I'm going to have to rethink the seal springs, because they won't do as they are now. That'll be this weeks challenge...

Regards
Warren

[RotarySMP]

Good effort Warren.

The Wankel is a little like the gas turbine, an incredibly simple design with very challenging details.

What do yu have in mind for your next seal material? There are a lot of things that use thin sheet spring steel (micro switchs "spring" to mind

[itsme]

Hi Mark,

It only seems to be the one seal that is causing major trouble. The first thing that I am going to try is adjusting the height of the small block underneath the spring. I've got a feeling that the spring may be 'too bent', if you know what I mean... I also didn't radius the blocks like it showed in the plans, so i'll do that. This will get rid of the 'violent' corners.

The wankel is a very strange feeling engine when it comes to compression. It is nothing like an equivalent 2 stroke or 4 stroke model engine. The compression from one flank sort of merges with the compression from the next, so there is never any free movement of the shaft. When one seal spring goes and compression is lost on 2 flanks, the shaft freely rotates 2 revolutions before any resistance is met. Every start attempt I have had so far has ended up with me having to open the engine up to find the seals giving trouble. Lets hope I can sort them out for good now, because having to rebuild an engine after every run could get annoying!

Regards
Warren

[devincox]

Awesome progress Warren!
Sorry no pics of mine yet. I started my housing in CI this weekend but the software problem is back. I thought I had it licked but it is still there, just very suttlely. The part "creeped" by about .100" overall. It is accumulating about .001 inch error per iteration of the cut.

Devin

[itsme]

Hi Devin,

It's a pity about that software problem. Have you contacted the company that makes it? Surely if they are trying to sell software for 'accurate' CNC machines they shouldn't allow a problem like that to even get close to the end-user and if it does, then they should fix it (free of charge)?

Today I am having a relaxing, non-engine day. I charged all the starter batteries last night and tried to start the engine this morning after making some modifications to the springs, but after about 5 mins of trying, the electric starter battery died thanks to my (rubbish) charger being dead. I have now got a new charger, but I'll have to wait about 12 hours before the battery is charged, so I'll try again tomorrow... I decreased the spring pressure quite significantly, and so far there has been no loss of compression. I think (hope) I have sorted out the spring problems.

Regards
Warren

[devincox]

Warren,
I have emailed the company I bought it from. I am sure he will get back to me very soon. I have had this software for years and have never had this problem, but I never tried to make an epitrochoid before. (c:

I'm sure you will soon have the springs all sorted out very soon as well. This way I can start planning the quad rotor design. (c;

Devin

[itsme]

Hello,

I tried starting the engine again this morning and still had no luck. It is firing, but still not running. I have opened it up again though, and I now have a BIG problem. I used 4 M2 grub screws to hold the spur gear in place and this mounting is completely inadequate. The gear has some free movement in its mounting. I need to remake the gear completely with a different, more sturdy mount. The problem with this, is that it will now interfere with the rear bearing. I can't move the rear bearing further back either, without remaking the eccentric shaft. The only possible solution is to make a new gear and use a bronze bush in place of the rear ball bearing. I'm also not sure whether my modifications to the seal springs will do or not.

Regards
Warren

[itsme]

Hi there,

A bit of work is still needed on my engine. I am going to make a new spur gear - this time with a MUCH sturdier mount.

I have also decided that I am going to dump the current seal spring setup, along with the current seals. I don't like the straight springs with a block underneath - it's too fiddly. Instead of this I am going to work on some OS/Mazda style springs (If I can get the materials right). At least I know that this spring setup DOES work. There are a couple of reasons why I am going to make new seals as well. The first is that the current seals have got a cutout on their bottom edge, which isn't suitable for the new springs and the second reason is that a radius on the top edge is necessary. I just got rid of the sharp corners on the top edges of the current seals, but a proper radius is needed. Without the radius, the seals have far more in and out movement than they should, which then makes the springs work much harder - probably a big factor in my current spring issues.

This engine has taught me a lot and I now have a fairly good idea as to what I need to watch out for on my next engine. I only have 2 weeks of holiday left now, so I need to try and get these modifications done in this time, along with the z-axis on my mill.

Regards
Warren

[Ken McKenzie]

(Just as a matter of interest, does anyone know anything about the cooling system on the DKM 54 engine (the first running wankel). I know that the fuel/air mix passing through the rotor and its shaft did a lot of the cooling, but I'm not too sure on how the trochoidal housing was cooled. I have seen photos of the housing, and it doesn't appear to have any cooling channels in it and it would also seem rather complex to try and get coolant to this moving part. Any ideas? )


Warren this discussion is most interesting. I have personally made a DKM 54 engine design using Mazda 12A engine parts and was perplexed that it would not start. I was getting 90 - 100 psi compression and the power strokes tried to stop the starter motor motion. After much interior damage to the engine I finally realized that the engine is designed to run backwards anf forewards at the same time. All the action must take place when all the components are turning in one direction. The rotor turns at two thirds the speed of the housing therefore its working actions must take place in the opposite direction. if you visulize the housing as a stationary object you would see the rotor making the Wankel engine functions in the opposite direction to the housing rotation. The only reason the DKM (Rotary Piston Engine) started and ran I believe is the result of Wankel placing the spark plug on the wrong side of the rotor.

The DKM 125 which was a newer version had water cooling in the rotor and the internal housing.

For your information Mazda does not make a housing that is true to the rotational path of the rotor. I have made a machine for re finishing Mazda housings and had to modify it and make it adjustable to follow the curvature of different housings.

It would be ideal to have the housing compatible with the rotor path as there would be little up and down movement in the apex seal slot. The engine functions as the result of the apex seal fluttering back and forth within the slot as the compression pressures exert themselves under the seal. The springs and centrifugal forces do not have sufficient pressure to effect against the explosive pressures in the engine.

The rings in a piston engine utilize the combustion pressures that are designed to get behind the rings to function.

When cutting and finishing the eptochoid surface I have found that I cannot use a cutter or grinding stone with a larger diameter than the diameter of eccentricity. Using a larger cutter changes the geometry.

Cheers

Ken

[CJL5585]

Ken,
I would like to welcome you to the site.

Appreciate your input. You will be a valuable guy to have in this forum.

Again Welcome.
Jerry

[itsme]

Hi there,

I was wondering if anyone (probably Mark, maybe Ken...or anyone else who knows...) would be able to help me with the detail of a mixture (charge) cooled rotor on a wankel engine. Some of the Sachs engines used this rotor cooling method, and I think the Nortons also used it.

As far as I can work out, the side covers have large cutouts in them and the rotor also has cutouts right through it. The charge then comes from the carb and passes through the cutout on one side cover, through the hole in the rotor and out through the cutout in the other side cover. As far as I can tell, this is correct up to here (isn't it???). I am then a bit blurry with the detail from there on. Does the charge then carry on to 2 side intake ports or only one side intake port? Can peripheral intake porting be used with this cooling method? Can anyone give me some more info on this setup and how it works???

I have never paid too much attention to cooling and lubrication, because the small model engines tend to just 'ignore' these problems - sadly it doesn't work that way with bigger engines.

Ken, as Jerry said, welcome! I think I have spoken to you before via email about the DKM 54???

Regards
Warren

[Ken McKenzie]

Warren
the Sachs engine kept the rotor cool by having the intake charge transfer through a port close to the eccentric bearing then flow out a side port in the rotor through to a tunnel in the side housing that led to the engine intake port.

I have the opinion that these are high speed dirty short life motors.

Why don't you clean your engine design by making a side seals from a bronze pipe the same or slightly smaller than the diameter at the bottom of the seals.

True the surface of the end of the pipe then cut about 1/8" off then do the same for the second ring. Find two neopreme seals close to the same diameter and then mill grooves in your rotor to set the seal and ring into with them having a slight pressure against the housing. The oil will protect the neopreme from being damaged by heat. The combustion pressures will try to make the neopreme ring oval and increase the sealing ability.

Mazda has two seals on each rotor side the inside one is for oil and the outside one is to provide sufficient compression for the engine to start at 250 rpm. These seals consist of metal and neopreme.

If you study the ports on your engine you will see that the intake stroke also draws through the exhaust port at the same time. At high speed this problem gets eliminated by the inertia of the flow. But if the engine does not start you can't attain the high speed necessary.

Therefore I believe you may be taking a leap in the right direction if you design and utilize a one way valve for the exhaust port

Hope this helps

Ken