Author Topic: 2.5cc tether car  (Read 4680 times)

Offline Old School

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2.5cc tether car
« on: March 26, 2020, 09:24:12 PM »
You liked the Mercedes this is something modern also from my workshop.
This is one of my modern tether cars powered by a 2.5cc glow plug engine with a tuned pipe. Fuel is 80% methanol 20% castor oil. Engine revs to around 40,000. Hold the British record at 262kph.

Offline awake

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Re: 2.5cc tether car
« Reply #1 on: March 27, 2020, 12:06:52 AM »
40,000 rpm ... 262 kph ... I'm having trouble wrapping my head around either of those numbers. Wow!
Andy

Offline Old School

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Re: 2.5cc tether car
« Reply #2 on: March 27, 2020, 06:56:04 AM »
The engines have a short life about 10 fast runs, then they need a new piston making and fitting.

Offline nj111

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Re: 2.5cc tether car
« Reply #3 on: March 27, 2020, 11:01:58 AM »
Wow that's insane! My father told me a bit about tether car racing as he had some involvement I think in the 1950's.  Is there much club activity these days? (or I should say was there - prior to the current lockdown situation)
Nick

Offline Old School

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Re: 2.5cc tether car
« Reply #4 on: March 27, 2020, 11:19:22 AM »
I do most of my racing in Europe with the modern cars, there is a track in Lincolnshire but only suitable for old timer cars.
We have almost finished a track at the BMFA ( model aircraft) Buckminster site but the virus has beat us to having trial runs to prove it’s ok for the modern cars. Picture of track attached.

Offline Vixen

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Re: 2.5cc tether car
« Reply #5 on: March 27, 2020, 11:53:26 AM »
When I was a lad, there was a tether car track a few miles away. They had cleared out a disused sewage settlement tank, still with a circular wall all round. Very bumpy surface so speeds were low, no record breakers there.

Mike
It is the journey that matters, not the destination

Oh! sod the journey, lets hit the bar and pool instead.

Offline cnr6400

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Re: 2.5cc tether car
« Reply #6 on: March 27, 2020, 12:57:15 PM »
GB010 looks like a screamer! Thanks for sharing the pics!  :ThumbsUp: :ThumbsUp: :ThumbsUp:

Offline JC54

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Re: 2.5cc tether car
« Reply #7 on: March 27, 2020, 01:42:26 PM »
Good afternoon Old School, I live only about 4 miles from buckminster track so will have a look when racing/flying resumes.   John  :old: :DrinkPint:
When the Fun Stops,, Stop!

Offline Rick Doane

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Re: 2.5cc tether car
« Reply #8 on: March 27, 2020, 02:50:22 PM »
That is a very nice car Old School and I like the tuned pipe also.  Did you make that one?  Mr. Jack ODonnell in the USA and Mr. G. Picco in Milano built some fast cars and were always great advocates for model engine building.  The speeds you guys obtain are fascinating especially keeping fuel flowing to the engine.  I would expect that there is little taper in the pistons considering only 10 runs per piston/liner.

Regards.....Rick

Offline Admiral_dk

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Re: 2.5cc tether car
« Reply #9 on: March 27, 2020, 03:13:27 PM »
While your handle "Old School" matches the "Mercedes" just fine - it isn't really a for for this one, where the only hint is British Racing Green  :praise2:

Record holder  :praise2: well you are not alone here (not me) - there are a few very fast boat guys here too.

I read that the current state of affairs with model car speed records - there is a problem to get the engine "on the pipe" ..... I do not see any attempts at changing exhaust timing / length, nor throttle to help with flow through the carb ....  :thinking:

Per

Offline Old School

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Re: 2.5cc tether car
« Reply #10 on: March 27, 2020, 05:51:22 PM »
Yes getting them onto the pipe requires a young fit horser that knows what he is doing the problem is no one is getting any younger.
My care runs very moderate exhaust timing of 195 degrees and a pipe length to match it.
To go really fast some of the racers are using in excess of 200 degrees of exhaust and short pipes.
Something has to change in the way the engines are set up so that they can be got onto the pipe a lot easier than what is happening at the moment. The challenge is what to change and keep the speed. You can only do so much on a test rig, the cars need to be run on the track.

Offline Admiral_dk

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Re: 2.5cc tether car
« Reply #11 on: March 27, 2020, 08:23:23 PM »
The Boaters inject water into the exhaust as this moves the peak power of the pipe down to lower RPM's and this works perfectly - then again they have a very "convenient water tank" at hand (or more correct at the rudder) .....

Being an Electronic Technician, I had thought about a very small control unit for a variable exhaust timing several times - but it hit me just now, that you only need this for a few times round the track at the beginning of the run ...!!... So why not have a small water tank onboard, that starts spraying water into the exhaust just after the engine fires ????
This could probably be done with pressure from the exhaust itself (or the crankcase) as it is two different places in the system with different pressure + a one-way valve would help. The extra weight should not have much influence as the tank will be empty before the car reaches the really high speeds and the engine will produce much more torque @ lower RPM's just after starting ....  :thinking:

Per

Offline Old School

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Re: 2.5cc tether car
« Reply #12 on: March 27, 2020, 09:09:53 PM »
I would struggle to find space for a water tank, plus most of us are close to maximum weight.
We control the initial acceleration by the vent pipe in the fuel tank at the start of the run the vent is submerged giving a lean setting as the fuel is burnt off the vent comes out of the fuel giving a richer setting also helped by centrifugal force.
The car still needs the help of a horser to get it on the pipe.

Offline Vixen

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Re: 2.5cc tether car
« Reply #13 on: March 27, 2020, 10:39:50 PM »
Didn't strictlybusiness1 discuss water injection into the tuned pipe a few weeks back? If I remember correctly, the organisers outlawed it by classing the injection water as illegal fuel.

Water injection must have worked if it was outlawed. It may be worth a search through the strictlybusiness1 posts.

Mike
It is the journey that matters, not the destination

Oh! sod the journey, lets hit the bar and pool instead.

Offline Admiral_dk

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Re: 2.5cc tether car
« Reply #14 on: March 28, 2020, 11:13:32 AM »
I'm pretty sure that it is Lohring Miller who has most experince with water Injection in the exhaust, as he even wrote a Tech Paper on the subject (that has been shared here a few times) - but I'm sure you're right that Jim was punished for using it as you mention Mike.