A work of pure genius! - Brilliant "Revetec" Engine

[hightower99]

Originally Posted by Matra et Alpine

ht, as I've friends with trikes then I can assure you that most of them are extremely light and very easy to maneouver. Without the need for a bodyshell and especially GLASS they are very light
and re frontal area, it is only that. It's not the width x height. That's ok for most cars, but bikes and trikes are a different shape and so their actual frontal area presented to the airflow is much lower than cars.

Yeah actually now that I look at a few more pictures of GTM trikes from the front and back the frontal area really isn't that big and they are light.

But the huge open wheels and long shape is probably not very aerodynamically efficient at all.

[revetec]

Originally Posted by hightower99

Do not question my understanding of power. Power isn't arrived at (it isn't just a calculated value), it is produced.

Are you aware that most dynamometers have a retarder and a torque load sensor. This is more accurate than driving a generator and measuring how much power is produced. We do measure power and what is produced, but on our dyno (like most dynos) it is a calculated figure. I'm sorry if you are looking too much into my statement. I was merely pointing out what is measured on most dynos and what is calculated. Most people know power and torque go hand in hand, so don't dwell on it.

Originally Posted by hightower99

Umm why not use a 4.5:1 reduction gearbox? This would allow full power at 3000RPM prop speed. But again as you stated you still have to think about reliability and a high stung DOHC 4VPC engine running at 13500RPM for long periods of time doesn't instill a sense of reliability.

For a start, an aircraft engine is under more load for longer periods of time compared to any engine in a vehicle. It is not uncommon to fly at 3/4 throttle for two hours straight. This is why avgas has been used to reduce detonation due to the high chamber temperatures under this type of condition, and why aircraft engines generally run a lower compression ratio. I don't know how the R600 engine would perform at 13,500rpm under 3/4 loading for over two hours straight, again and again. My thoughts is that the combustion and engine temperatures would be too great, and the reliability and service intervals would be drastically reduced. But, until it is tried, no one will know.

Originally Posted by hightower99

Power will only increase if sufficient torque is produced at the higher RPM, which brings up another interesting point. If you are achieving good peak piston speeds with the cam (trilobe) design meant for aeromotive use then you are going to have to reduce the leverage (ie radius) of the cam to achieve the higher speed of 6000RPM (in fact the mean radius will have to be cut in half to achievce the same piston speed at 6000RPM) which means torque will be reduced.

I said automotive camshafts (meaning valve cams) not trilobes. Trilobe shape is the same, like keeping a conventional engine's stroke the same.

Originally Posted by hightower99

That is interesting news. Is it possible that you might give me a copy of the spreadsheet program?

Sorry. Before I designed the X4 engine I spent three months of research gaining data and spreadsheets from over 6 universities and linking them up to a detailed data calculation sheet including our data and trilobe force rates and piston accelerations etc. I'm not going to give up 3 months of my research to anyone.
I can say that the sheet gives me expected power, torque, volumetric efficiency, suggested valve and port sizes, suggested valve lift, intake port lengths for ram induction as well as organ pipe induction, optimum stroke, valve piston clearance, exhaust intake flow ratio, piston velocity and acceleration, camshaft data such as suggested degrees of openings and closings as well as overlaps, volumetric efficiency calcs, power and torque estimations including turbo non-turbo and intake air temps, Power and torque graphs, injector sizes and flow rates, performance predictions, and transmission ratios to suit listing 24 major transmissions and ratios. It has more than that including all engine data.
Input data includes Bore, Stroke, Cylinders, Trilobe diameter, piston bearing diameter, conrod ratio, deck height, piston crown height, head gasket thickness, head gasket inside diameter, piston valve dome/relief volume, combustion chamber volume, head flycut diameter, head flycut depth, intake and exhaust valve diameters, Intake and exhaust stem diameters, Planned top RPM, Desired peak power RPM, Desired peak torque RPM, Air temperature ...etc....

It is quite detailed taking up 12 spreadsheets. I designed the current engine using calculations to provide maximum torque at 3,000rpm and maximum power at 3,500rpm, and that is exactly what we got on the dyno, so it's pretty accurate.

Originally Posted by hightower99

Again I ask: how did you size the throttle for the engine? At 25% throttle the engine should only be producing 1/5 to 1/4 of peak torque over the rev range.

My spreadsheet suggests valve and port sizes. I then looked at other engines with that port size as well as my own volume calculation and found that the turbo Subaru EJ20 throttle body was about the right choice. Our engine has a very unusual characteristic in the lower RPM ranges as I have stated. At 10% throttle (measured by the throttle sensor) at 2,000rpm we are producing 85Nm of torque, which is just under half the torque at WOT. At lower RPMs this percentage of torque produced is greater and at higher RPMs it is lower, due to increased airflow required in higher RPM ranges.

[revetec]

By the way, the X4v2 with automotive style camshafts producing 193hp@5,200rpm with me sitting on the trike (110kg) with the new transmission etc.. my spreadsheet says the performance prediction on the quarter mile time with good gear changes should be around 10.13seconds and an trap speed of 217kph. Although the calculation is done using a conventional type engine calculation. It'll be interesting to see in practice what we will achieve. What will be really interesting to me though is how much fuel will be used to do so.

It also says that If I lose 20kg it will be just in the sub 10secs. I'll have to go on a diet. :-)

Correction: The trike weighs 450kg with engine so producing 193hp@5,200rpm with me on the trike should do a quarter mile in 10.81secs with a trap speed of 203.47kph. I'll have to lose more weight. Shane should do a 10.68sec and 206kph.

[hightower99]

Originally Posted by revetec

I said automotive camshafts (meaning valve cams) not trilobes. Trilobe shape is the same, like keeping a conventional engine's stroke the same.

So the only thing that you are going to change is the valve cams? What about piston speed? If you can just double the RPM without changing the trilobe radius then what sort of piston speeds are you achieving now? Is the timing between the pistons and the output shaft the same as a conventional engine (180deg per stroke)?

[hightower99]

Originally Posted by revetec

By the way, the X4v2 with automotive style camshafts producing 193hp@5,200rpm with me sitting on the trike (110kg) with the new transmission etc.. my spreadsheet says the performance prediction on the quarter mile time with good gear changes should be around 10.13seconds and an trap speed of 217kph. Although the calculation is done using a conventional type engine calculation. It'll be interesting to see in practice what we will achieve. What will be really interesting to me though is how much fuel will be used to do so.

Sounds good.

I am guessing 110kg is your weight right? What does the GTM trike weigh with the revetec engine?

Do you have any reference numbers from conventional engined trikes?

Maybe GTM can answer as to what the 185HP trike can do in 1/4 mile?

[revetec]

Yeah go one and hassle me over my weight ;-) Yep I'm actually 112kg.

The trike with the engine is about 450kg.

Like I said, the calculation may not be accurate as there are other factors not taken into consideration due to the type of calculation. I'll be interested what GTM trikes do on the quarter mile with the current engine and what we get in actual tests.

[revetec]

Originally Posted by hightower99

So the only thing that you are going to change is the valve cams? What about piston speed? If you can just double the RPM without changing the trilobe radius then what sort of piston speeds are you achieving now? Is the timing between the pistons and the output shaft the same as a conventional engine (180deg per stroke)?

Our piston acceleration rate is below a conventional engine. I'm not going to divulge our piston acceleration rates and/or con-rod ratio at this point. Sorry.

Yes we have 180degrees of rotation of the output shaft per stroke. Trilobes are rotating 60degrees.

[hightower99]

Originally Posted by revetec

Yeah go one and hassle me over my weight ;-) Yep I'm actually 112kg.

Well I can't hassle you over weight because I weigh 130kg

but then I am 205cm tall.

Originally Posted by revetec

The trike with the engine is about 350kg I think.

Thank you for the info.

Originally Posted by revetec

Our piston acceleration rate is below a conventional engine. I'm not going to divulge our piston acceleration rates and/or con-rod ratio at this point.

Good to know but I asked about peak piston speed not acceleration. If you are capable of running at 6000RPM then I might assume that peak piston speed approches 20m/s at 6000RPM in which case it is less than 10m/s at 3000RPM. Am I in the ballpark or does the revetec engine allow greater piston speeds? or maybe it is able to achieve even 6000RPM without coming close to 20m/s even when generating all that torque? I remember that the piston stroke was released but what about the mean radius of the trilobe (that is afterall what really determines the leverarm length).

[revetec]

We can have higher piston speeds and we have tried it many times. We slowed the speed down and increased torque throughout the entire rev range even at the low end. Strange thing is that all published theory on this says otherwise, but we have proven it in dyno testing.

[Kozy]

Brad I have been reading you thread and keeping an eye on your website with intense intrest recently. (Ok to be honest, I have only been reading this topic since 6pm today!)

I first noticed your website in around june last year, and found the concept facsinating. (please excuse my spelling, it is nearly 3am and I am somewhat tired after reading for so long!)

I decided to take you concept and use it as part of my final year dissertation project at university, to see if the design could be optimised for a high speed performance road car design.

After reading this page, a lot of issues have been thrown up, most of which I have had exactly the same thought process as yourself and having effectively developed my own version in a sense I had a somewhat better understand of the mechicals than some of the serial naysayers here.

I do have a lot of technical questions I would like to ask you with regards to design, most importantly the profile of the trilobate, which I simply cannot seem to get right in my CAD drawings.

I will be contacting you shortly with a few questions when I am less drowsy and confused.

Here is a Solidworks render of my work to date.



I would like to add as a sort of disclaimer, I am in no way trying to steal interllectual property of Revetec, nor imply any of the original idea is any of my doing. All references of the original idea in my paperwork clearly state that this is Brads design, patented by Revetec etc etc.

I have no knowledge of patent laws and I hope for gods sake I am not breaking any, I am simply and engineering student with a profound interest in the technology and abelief that it can work. The CAD model helps me to understand the workings better and analyse the engine in some very basic forms.

Regards

Dan

[Kozy]

Also, may I ask if there was any decent technical discussion regarding this engine between page 30 and here? I got fed up of reading the same repetive drivel over and over and jumped to the end to introduce myself!

[revetec]

Dear Cozy,

Great render and model. One comment though...Is the camshaft drive pulley on the same shaft as the trilobes? If it is, then the drive gear needs to be at a 3:2 ratio, not a 1:2 ratio.

Do you have a 3:1 output shaft below the trilobe shaft as we are using this to give 1 stroke per 180 degree output shaft rotation as is in a conventional engine. We extend this shaft through the front of the engine and then use a 1:2 drive for the camshafts.

Sorry about trilobe design, currently it is confidential. It is tricky to design. You cant just profile it like a normal cam.

Keep up the good work!

[Matra et Alpine]

Originally Posted by Kozy

Also, may I ask if there was any decent technical discussion regarding this engine between page 30 and here? I got fed up of reading the same repetive drivel over and over and jumped to the end to introduce myself!

Welcome Dan.
Which Uni are you at ? If you can put your approsimate location in your profiel it might help in future.
Nice rendering .... any chance of a 3d animated model ?

PS: Good call on the thread, you get used to it I see Brad's already responded on the confidential stuff. If it's critical to the thesis I know there are things you and the UNi can do to protect Brad's invention. My own thesis was closed-book for a number of years !!

[Kozy]

I am an Oxford Brookes student.

No chance of getting an animated model of the entire engine at present, I did start working on one, but only having a laptop, the processor can't really handle it! I have a basic one akin to what Brad has posted on his site, but I will post no more than the render above as to respect Brads privacy. (I used this particular render as it does tend to cover up a lot of the internal workings!)

A very good point on the camshaft pulley, I had not thought of that one. At present, I was going to use the the standard 1/3rd output speed, but design the engine as a high speed racing unit, with say a output equivalent of 12,000rpm in a stanard engine. My belief was that using this method, coupled with a diesel gearbox optimised for a 4000rpm road car, could produce the kind of performance required. Obviously people here have gone over this issue in great deatil, so I am having my doubts about that route now, however I have not yet come to working out the theoretical power formulas etc to disprove that this would work. I have to do this as sadly I cannot take the word of people on a forum, it's just not good university practice you understand!

I understand the confedentialliaty of the trilobe design, I will attemt to get my design to work properly to the best of my understanding. the Only problem is that I cannot get both bearings to follow the opposing faces.

This model was created entirely from reference of the internal render of either your 2003 or RHL4 engine, and is simply my interpretation, without knowing any techincal deatils at all. I currently use a 4:1 transfer shaft, although in hindsight, 3:1 would have been a smarter move!

One thing my tutor and I have noticed, which you have somewhat agreed with, is that the standard equations for power and torque will not work on this engine per se, we are currently picking apart these formulas to see if they can be rewritten to apply to this design. That is, formulas for indicated power and torque, which are rather more complicated than 'Power = torque x rpm'!

[hightower99]

Originally Posted by Kozy

I understand the confedentialliaty of the trilobe design, I will attemt to get my design to work properly to the best of my understanding. the Only problem is that I cannot get both bearings to follow the opposing faces.

Good luck with that. If I was you I would first decide the function of the motion I wanted the piston to follow. From there creating a trilobe cam to produce that motion against roller bearings is almost exactly the same as with a conventional cam working against roller bearings. Of course you have to make sure that the radius changes equally on both sides at the same time (to hold the pistons on the dual trilobes) but you know that already I hope.

Funny that in your rendering it seems that the closest piston set has somehow fallen off the trilobe (the piston is close to TDC but the trilobe is in the same position for both front and rear pistons and the rear piston is close to BDC).

Originally Posted by Kozy

I currently use a 4:1 transfer shaft, although in hindsight, 3:1 would have been a smarter move!

Why did you even consider 4:1? Out of curiousity, how are you synchronising the counter-rotating trilobes?

Originally Posted by Kozy

One thing my tutor and I have noticed, which you have somewhat agreed with, is that the standard equations for power and torque will not work on this engine per se, we are currently picking apart these formulas to see if they can be rewritten to apply to this design. That is, formulas for indicated power and torque, which are rather more complicated than 'Power = torque x rpm'!

First the formula is:
Power (HP) = Torque (lbs-ft.) x Angular velocity (RPM) / 5252
(5252 is a constant that only applies when using HP, lbs-ft. and RPM. Using other units will result in different constants).

Second: How does that not apply to the revetec engine? Please explain.