Building your own Dyno

Dirt Bike Technical discussion. This is for a little more in depth discussions :-)
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Crofter985
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Re: Building your own Dyno

Post by Crofter985 »

Had a look on eBayUK last week and found this up for auction.
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Put a bid on it at the start price and it ran for the three days it had left to run without being challenged.
It's a 330x400mm slug of steel, two sets of bearings, a disc, caliper and master cylinder, a starter ring and starter motor for said starter ring. Now there's a good few other bits to get but that's a good start. It's not all plain sailing as far as the rotor is concerned it's only big enough for 50hp but what I am thinking of doing is to get some discs of 50mm thick steel made up and fit them to the ends, or I've just had a thought, get another slug of steel the same size and make a double roller set up that the wheel sits in. There's a few interface box options, I will have to do some detailed research before I buy. Once I gave a roller setup working it will be possible to do comparative testing without electronics just by timing runs, probably not much use for any kind of accuracy, what it will be able to do is a quick dry and warm ( important factors in winter round here ) way of setting carb up, getting A/F ratios set up and so on.
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Sandblaster
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Re: Building your own Dyno

Post by Sandblaster »

I've been contemplating this idea.
If I go through with it I want to make mine wide enough so that I can dyno Quads as well as bikes.
I don't even own a quad but as soon as people find out you have a dyno they will seek you out :D
If bikes are for kids I'll never grow up.
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Crofter985
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Re: Building your own Dyno

Post by Crofter985 »

Que whispered voice in the distance.....

"If you build it, people will come"

Like that? :lol: :lol: :lol:
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Sandblaster
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Re: Building your own Dyno

Post by Sandblaster »

Yep... Just like that :lol:
If bikes are for kids I'll never grow up.
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Crofter985
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Re: Building your own Dyno

Post by Crofter985 »

I spoke with a guy today who seems to know his stuff, he says all you need is a plug in, PC interface oscilloscope and you can get them off eBay for 50 pounds or what would that be 70-80 dollars? Then feed it into Microsoft excel?
I've got a few more questions myself now so I'm going to get in touch with him again and se what's what, but it looks like there could be a very cheap option.
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Sandblaster
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Re: Building your own Dyno

Post by Sandblaster »

Whohoo!
If it works out you will start a new fad and all the bikers will be building their own dynos!
If bikes are for kids I'll never grow up.
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Crofter985
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Re: Building your own Dyno

Post by Crofter985 »

A bit of an update on the dyno, I kinda forgot about this thread.
I went to a local engineering company with the roller, we spoke about what could be done with the roller to mount it, the result was stub shafts for each end. They had some 80 or 90mm EN8 steel shaft which was ideal but no discs of steel for flanges. To get a disc of steel profile cut was going to be a crazy price, there has been a big upturn in oil and gas related activity around here and getting things like that done is becoming very expensive when time is added. But a visit to another engineers shop turned up some pipe flange blanks that are going to do the job just fine, £18 each, that could hardly cover the cost of the steel, they must be from China, 8 bolt holes around the circumference, 8-9" diameter.
So I left it all with them and then after a couple of weeks I got a message to call the engineers. They had checked up on the spec of the bearings I supplied, the ones I got with the roller. They were waaaay under spec, most bikes will get the roller to 3000rpm with sports bikes getting on to 4000rpm, the bearings in the eBay lot could do a max of 1200rpm, well that makes the buy not so great but hey, it's probably still a very good buy.
I went online and found a bearing sales company after getting no joy contacting bearing manufacturers directly. The salesman said the problem was with the bearings I had were grease lubed and oil bathed was what I needed. Ok, long story short, £90 each with the seals required.
So I got them in just a few days as the guy had them in stock. They are rated to take the weight of the roller ( which I think is 330kg) at 4000rpm.
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Sandblaster
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Re: Building your own Dyno

Post by Sandblaster »

Wow!
It's a good thing you checked on it because a failed bearing is cause for a serious shop accident.
Post pics when you can.
Thanks buddy!
If bikes are for kids I'll never grow up.
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Crofter985
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Re: Building your own Dyno

Post by Crofter985 »

Yeh I should have had pics, the last day I was in the engineers shop my phone was out of action.

The chassis is going to be built around a H beam I got in exchange for some old scrap that I gathered up from around the house.
I'm going to get it blasted clean before I start building it up. I think I'll make it nice and heavy to damp out any vibes. I watched a video on YouTube of a guy who built a dyno and the chassis walked along the ground with the tiny amount of vibration it had.
A bit of weight won't do any harm.

The electronics, the interface, is from this company......

http://www.sportdevices.co.uk/dyno/sp1.htm

I looked at a few different ones and I could have got a interface for around £600 but the sport devices interface was recommended to me by the guy I got the roller off, he had a dyno up and running with the equipment and also the spec, or resolution of the speed monitoring is quite a bit above the cheaper alternatives. Here is the spec......
Image
The roller came with bearings, a starter, a starter ring, a disc brake, a caliper and a master cylinder. Along with the starter and ring being for starting a bike with no other starting method, the starter ring is for the sensor to count the teeth of the starter ring. It says it's up to 15khz that's able to count 15000 teeth a second, that's up to 225 teeth at 4000rpm, I've never counted the starter ring I have but I don't think it will be as much as that.
There's a lot to do yet on this project, hopefully it will all come together and I can do some power measurement by sometime next year.
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Crofter985
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Re: Building your own Dyno

Post by Crofter985 »

Oh yes and credit where credit is due, it was the engineer who convinced me to look for better bearings, I was all for just using the ones I had. I was kinda arguing that it would only be for short cycles of speed. The old guy assured me it would not take long to go wrong if it was going to go wrong. So I looked at the roller diameter again and saw the top rpm of 3000 I had originally thought was the max, well it would be for 80 to 100hp bikes but if I put a sports bike on it it could be turning it at 4000rpm, when I saw those numbers I knew the 1200 rpm bearings did not really stack up well at all.

The interface sitting at home patiently waiting for me to get the rest of it done.
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