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Our bearings were grease lubricated and were only replaced once.  Considering we ran to 20,000 rpm frequently and 25,000 rpm occasionally that's pretty good service over 10 years.  You will be running way over the maximum rpm for the clutch.  That's another reason to prefer a positive type clutch.  Does Dave's second dyno even use a one way clutch?  The belt will make a great fuse if it holds up to normal running.
Lohring Miller
GMN also has models that are sealed with grease or oil lube.

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6 hours ago, LohringMiller said:

Our bearings were grease lubricated and were only replaced once.  Considering we ran to 20,000 rpm frequently and 25,000 rpm occasionally that's pretty good service over 10 years.  You will be running way over the maximum rpm for the clutch.  That's another reason to prefer a positive type clutch.  Does Dave's second dyno even use a one way clutch?  The belt will make a great fuse if it holds up to normal running.

Lohring Miller

 

I was thinking the oil drip lube would have the least amount of friction (hopefully) making the power numbers more accurate, plus I'll be running closer to 30K and beyond if I test 21's and 45's.  This will (of course) require a smaller wheel but I want that capability down the road.

I'm hoping the one-way bearing will hold up, seems to be doing fine on my buddies dyno.  I really, really like the idea that if the motor seizes suddenly the wheel can keep motoring, especially since I probably won't have as solid a table as yours.  Also I wouldn't be real happy closing the throttle suddenly therefore shutting off lube to the engine and still have the wheel drag it along at 25K+ until the main clutch disengages at around 15K.  That right there could cause a catastophe! :o

Not sure if Dave is running a one-way or not, I'll ask him... :)   

Edited by Terry Keeley

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I think that oil mist lube is lowest friction, but drip is a close 2nd. Just make sure that bearing doesn't fill with oil. Need to have a way to shut off oil when not turning

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On 1/10/2019 at 11:02 AM, tnrcboatracer said:

Terry, is 13.5 Nm torque capacity enough? The GMN FP427Z sprag clutch has 94 Nm torque capacity.

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Lohring can confirm this but our biggest motors might make 25-30 inch-pounds of torque, 13.5 Nm is about 120 in-pounds so that's not an issue.

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Lohring can confirm this but our biggest motors might make 25-30 inch-pounds of torque, 13.5 Nm is about 120 in-pounds so that's not an issue.
Hreat. I had no idea hoe much torque a 67 produced.

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11 minutes ago, tnrcboatracer said:

I think that oil mist lube is lowest friction, but drip is a close 2nd. Just make sure that bearing doesn't fill with oil. Need to have a way to shut off oil when not turning

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 Gonna use this type:  http://www.lubriteindustries.com/downloads/drip-feed-oilers.pdf

They have a needle valve to adjust the flow plus a sight glass and shut off.  Was thinking I'd drill a small hole in the pillow block that holds the bearing with an outlet right at the back of the bearing in the ball area then attach these to the top.  Probably leave the shield on the outside and remove the inner. :)

Edited by Terry Keeley

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I have not used a one way bearing on either of these dynos. At first I would blip the throttle when the flywheel was slowing down after a run, but in practice the flywheel disengaged pretty quickly. If there is a brake on the flywheel then it can be slowed very quickly. One of those things where it is possible to overthink what in practice is quite simple. On the first  dyno in the previous pics (roughly based on info Lohring kindly provided) I used 2 couplings with a square shaft between the motor and the clutch but the square material twisted pretty quickly and I changed to having the clutch directly on the engine. The downside being the time taken changing motors over but in practice I mostly used one crankcase with different cylinders. I did hundreds of runs without a problem.  On the belt drive dyno I have a coupling between the motor and cluch so that I can easily swap between motors and also use it for 91 nitro engines. 

Edited by DaveMarles

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What Dave said.    Your picture is close to what I'm considering for my new dyno.  Thanks.  Watch the flywheel diameter if you plan to test nitro engines.  We melted the piston on all (3) 11 cc nitro engines we tested. 

The first inertial dyno for model engines was designed and built by Marty Davis and Brian Callahan.  John Ackerman built the dyno.  I found an article on it at https://web.archive.org/web/20030205134346/http://rcboat.com:80/dyno.htm   and https://web.archive.org/web/20030209190150/http://www.rcboat.com:80/dynotech.htm It has calculations and mentions that they used a 3.75 inch diameter by .75 inch thick flywheel for .45 cubic inch engines.

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Marty’s dyno needs new bearings but other than that I think it’s in tack. We talked about rebuilding it a few years ago when I started back racing boats but we haven’t gotten serious about it since. 

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51 minutes ago, LohringMiller said:

What Dave said.    Your picture is close to what I'm considering for my new dyno.  Thanks.  Watch the flywheel diameter if you plan to test nitro engines.  We melted the piston on all (3) 11 cc nitro engines we tested. 

The first inertial dyno for model engines was designed and built by Marty Davis and Brian Callahan.  John Ackerman built the dyno.  I found an article on it at https://web.archive.org/web/20030205134346/http://rcboat.com:80/dyno.htm   and https://web.archive.org/web/20030209190150/http://www.rcboat.com:80/dynotech.htm It has calculations and mentions that they used a 3.75 inch diameter by .75 inch thick flywheel for .45 cubic inch engines.

 

Why did you melt the pistons?  Too long a run up time?

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John,

How much would the bearings cost?

It would be nice to get that Dyno back to work?

Could you ask Marty or Norm what it would take to make this happen again?

I would be willing to pay for whatever it needs to get it back in service.

I think there is a lot of useful information that a good Dyno will provide us all.

Thanks,

Mark Sholund

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38 minutes ago, Terry Keeley said:

 

Why did you melt the pistons?  Too long a run up time?

I think the load from a 5" flywheel was too high.  We saw around 4 hp just before the peak when the engine failed.

Lohring Miller

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2 hours ago, shoboat said:

John,

How much would the bearings cost?

It would be nice to get that Dyno back to work?

Could you ask Marty or Norm what it would take to make this happen again?

I would be willing to pay for whatever it needs to get it back in service.

I think there is a lot of useful information that a good Dyno will provide us all.

Thanks,

Mark Sholund

I’ll ask and go from there. It’s been awhile and I don’t remember where we left off.

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