How about a 180 (30cc) glow motor?

[TimD]

Ian,

After my last post I went back and read our emails - it would need some tidying up to say the least. Still some good progress/ idea's/data can be seen if you go back to the beginning and see where we were at compared to what we know now.

What I was trying to mention regarding the A100 and a "strength issue" was that the rod/ piston / crank are not going to fail due to the increase in RPM.

How much metal is in the case of the A100 around the passages? Any room for improvement?

 

[EatMyShortsRacing]

Tim / Ian

Well we are going to find out about the port area of the 100. After running mine this weekend (yes the first practice day I have had in 3 years) and I will be pulling it down and doing my 'stage 1' modifications.

I only do one mod at a time so I can tell whether I am going forwards or backwards

EMS Racing

 

[TimD]

Craig,

Can you hold off on the port adjustments until we get the time / area details? You could potentially solve the time /area or case volume argument completely. We have narrowed down so many other potential causes 1 at a time and it is working it's @ss off so far. If the time /area thing doesn't work out then Ian's idea that the 16% difference incapacity with the same case passages / flow ability is about the only thing left.

Tim.

 

[EatMyShortsRacing]

Tim,

Port adjustments were not what I had in mind. Case Flow is where I am starting..

Craig ... oops EMS Racing

 

[Ian Inverarity]

Tim,

Like I said, some of that stuff should not be spread around! If you want to do the editing, go for it!!!

I would be confident of not having piston or rod failure considering the torque output of the A100 and peak revs I have seen from the A-90HP.

I have already increased the flow areas in the inlet and exhaust stub, but not the other passages in the case. There is no more to play with in the areas I have already modified.

Craig,

Do you have a tacho, radar or GPS? It will be hard to evaluate any improvement if you dont. ie on the weekend there were two props I thought were faster than the H-50, but on radar they were actually 10k slower....

Ian.

 

[EatMyShortsRacing]

Ian,

No I dont have either but I intend to use one prop and fuel and look for changes in performance.

Need to buy a radar I think...

Craig

 

[Ian Inverarity]

Craig,

A GPS is much cheaper and you dont need to drive a funny course or have someone holding it while you drive. The problem with a GPS is finding somewhere to put one. They cant see thru carbon fibre pipes (they need to see satellites) as I found out with the Hummingbird. Used one a lot on the mono tho, strapped to the radio box.

Garmin Etrex. Unfortunately it is generally cheaper to buy one from the US and ship it over than get one locally.

Ian.

 

[EatMyShortsRacing]

hmmmm maybe time for the DYNO!!!!! LOL

I almost had one when I had a friend working for Dyno Dynamics.... still have the basic idea... using an alternator to load the engine up...

Craig

 

[Ian Inverarity]

Craig,

A dyno would be nice! I have some ideas on how to do an eddy current dyno, but it is a background project. 8)

I also had an idea of how to do an onboard dyno. Measure the wind-up characteristics of a particular flex shaft (ie torque vs angle of wind up). Use a tacho and another device with a pickup at both end of the shaft to detect the wind up angle. Calculate and you have torque and revs from a run! Of course I am not smart enough to do the electronics for this.... :

Ian.

 

[TimD]

I had a similar idea to Ian's but on a bench using a Ducted fan unit to load the engine, and using a scale to measure torque reaction on the motor mount. Never got round to it though. Getting off -topic here :

Craig, use a marked course (doesn't have to be a measured course), drive consistently and use a stopwatch. should give you some idea of improvements and it is relative to how we race.

Drivers ready, dremel's set, Go!

 

[EatMyShortsRacing]

Hey I got it!!!

Dremel class!!!! We can all go an buy cordless Dremels and install them as the motor for a boat... We could even have Stock and Mod Dremel class!!! Or.... wait for it.... Outboard Dremel with the right angle atachment!!!

EMS Racing

 

[Ian Inverarity]

Tim,

It will need to be a measured course unless the bouys can be left in, otherwise how can you compare what was done with different engine mods on another day?

I think course timing is the best way to set a boat up for heat racing, but probably a radar or tacho is better for measuring incremental engine improvements! 8)

Hey Craig,

Dont be afraid to tell us what ou are planning for SC stage 1! ;D

Nitrocrazed racing: Oops, the Dremel slipped....

 

[EatMyShortsRacing]

Ian,

Stage 1 is just flowing the ports with some extra volume... no holes in bits yet. I will also (finally) do an induction disc that opens a lil longer and maybe change discs at the lake to see if there is any difference there too....

Have you checked the Carb diameters between the 90 and the 100 coz my 100 looks bigger... spose I should measure it huh???

EMS Racing

 

[Ian Inverarity]

Craig,

The disc timing will help the motor for sure. 8)

On my engines the carb is 12mm for both the A100 and every A90HP I have had. The A180V is 13mm.

Are you talking about flowing the transfer ports or the inlet passage? I havent ground the transfer ports in the case, that would not be an easy job.

Be carefull with the backplate, I now seal mine with a smear of that high temp copper colour silicone. I have noticed that these can leak otherwise.... Note to Mr A: extend case slightly to accomodate an O-ring groove on the backplate....

Nitrocrazed racing: There is no such thing as a prop that is too big, only engines that are too weak....

 

[EatMyShortsRacing]

Ian,

Who said I open the transfers in the case??

;D

EMS racing

 

[Ian Inverarity]

Hehe,

Okay Craig, what are you going to grind?

Ian.

 

[EatMyShortsRacing]

Ian,

The liner... start by turning the bottom down to give a more gradual entry, then shape it into the port... ending up with something that looks a bit like going over a wing in reverse....

Craig

 

[Ian Inverarity]

Back to the original topic: a 30cc single cylinder motor.

What is everyones preffered crankshaft and induction system layout? There is quite a variety used in current 90 designs.

Crankshaft designs: there are 3 main types that I am aware of.

-The normal system used by most engines smaller than 90's is a single sided crankshaft supported by 2 bearings. In 90's this is used by Rossi, Kalistratov, K&B, OPS and OS (that I am aware of). This type of crank can have a small pin extension of the crank pin which can be used to drive a Picco/OPS style disc valve or a drum valve. The OPS 90 is the only engine I am aware of that has this type of crank and a zimmerman disc induction. I am unsure of the crank layout of the Picco 90, it may be similar. This single sided design has the theoretical disadvantage of the crank counterweight being offset to the centre of mass of the pison and rod, but is the simplest system, and the most prevalent in engines smaller than 90's.

-Double sided crank supported by two bearings. This is used by CMB for their GP/EVO style motors. The two halves are pressed onto a crank pin trapping a rod between the crank halves. CMB also uses full circle cranks and steel rods with needle roller bottom ends, and I suspect the crank design was based upon kart engines where crankcase compression may be considered as very important. The advantage of this design is the counterweighting of the crank can be approximately even about the centre of mass of the piston and rod giving better balance for higher revs. Also this gives a very short compact engine. The disadvantages of this system is it is more complicated and expensive to make (although CMB seem to have made inroads into this) and the two halves can twist out of alignment, and dis-assembly of the engine is more complicated. This type of crank layout suits zimmerman disc on the non-driving end of the crank, but CMB uses a needle roller for that end so that the disc diameter can be kept reasonable.

-Double sided crank supported by 4 bearings. This is used by the A motors for the A-90HP, A-90LS and A100. It uses two crankshafts supported by 2 bearing each and a seperate pin that links them. The 2 bearings on each crank keep them in alignment so the pin is not a press fit, and the crank can be easily pulled apart. The adavantages is a very well supported stiff crankshaft with the counterweighting approximately under the centre of mass of the piston and rod, and the whole system can be pulled apart. The disadvantages is it is probably the hardest system to make, and is complicated, and the engine has 4 bearings to look after. This system uses a disc bolted to the rear crank, but could equally use a floating zimmerman disc.

What are the general feelings of preferences?

Nitrocrazed racing: We aim to please...

 

[Ian Inverarity]

Craig,

That reminds me of something we were doing to little Force motors to get them to go. We were cutting into the liner to make it thinner in the area of the transfer ports to effectively make the ports larger. Easy on the force motors because the liners were quite thick for the motor size.

Nitrocrazed racing: Where did I put that rotary table for the mill....

 

[TimD]

I have to say that I have been a fan of the first arangement as I like drum valves. However, after reading your description of the setup in the A motor's, it sounds more suitable and robust than the other 2 options. 4 bearings on the crankshaft to look after is no big drama - they will be taking less load than say a CMB arrangement anyway. More bearings on the shaft halves would allow better case / shaft clearance which would make for a better/ faster / more stable motor too.

The induction type is the drawback. What if we could encompass the induction port into the crankshaft half? Less parts - potentially easier to make?