Author Topic: DIY cams  (Read 482 times)

Gary Abbott

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DIY cams
« on: May 12, 2020, 08:12:05 PM »
Hi,   

Maybe of interest.. perhaps give the engineers here a laugh or hopefully inspire other novices like me to have a go.

Whilst I do have a 1st in Engineering, I abandoned the company that kindly paid for my uni scholarship within days of graduation and headed to the City of London to do nothing particularly exciting for the next 30 years. I now have lots of time on my hands and have been self isolating in my garage.

Firstly let me apologise in advance for basic health and safety, actually none, on my homemade copy cam grinding bench.

I have made a batch of BSAgoldstar vernier cams and the cost of materials and hardening works out at approx £25 per cam.   Commercial versions are approx £150 and my cams are a copy of the BSA 65-1891 and I am not aware anyone has these available.

I haven’t included the cost of my DIY grinding bench or my time on the lathe and mill.

Spec:
EN36 and one blank in EN351
Machined/ground to 6thou over
hardened to 60 RW to 20thou depth.

Final grind pending.

The Cam blanks are pretty simple/easy to machine and  given they fit into vernier gear, there is no gear to cut  :).     The main challenge was building the copy bench and getting this aligned and rigid. Grind wheel 3400 rpm.   Cam drive motor 25rpm.

Also tried a few different grinding wheels and found 46 grit  k hardness wheel gave good surface finish on pre hardened blanks.     Planning to use 46grit ruby or aluminium oxide wheel on the hardened cams. There  are some good research papers on wheel specs but would welcome any thoughts/advice on the best wheels to use pre and post hardening.

Regards Gary

Andy Pike

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Re: DIY cams
« Reply #1 on: May 22, 2020, 07:57:56 PM »
Hey Gary that’s impressive. Fancy tackling a Honda K4 cam on your rig? I have a blank. ATB.

Gary Abbott

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Re: DIY cams
« Reply #2 on: May 23, 2020, 11:16:58 AM »
hi Andy,
 

Yep I would be happy to do it.   but suggest we wait until I have carefully mapped/ measured the cams I have made to confirm level of accuracy.   

Also I went to Dyno yesterday with a  46 exhaust cam fitted   Will go again first week in June to try one of my 1891 cams back to back with a BSA 1891.  Hopefully accuracy/operation will be good. Will keep you posted.

I assume the Honda cam is for a twin.    What’s the length of the cam and distance between lobe centres?


Andy Pike

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Re: DIY cams
« Reply #3 on: May 23, 2020, 12:08:37 PM »
Understand you had a good day in the dyno.😉. My spy’s inform me that Andy’s exhaust was guide good! 😜. Maybe he could do me a new hip.........😩
I’ll root out the cam blank & measure that up, but yes, it’s the twin.
Cheers

Andy Guy

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Re: DIY cams
« Reply #4 on: May 23, 2020, 04:49:47 PM »
Sorry Andy but you are well past it at your age. Have yo tried the Vet?
Winners never qui

Andy Pike

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Re: DIY cams
« Reply #5 on: May 24, 2020, 12:24:55 AM »
Daren’t go to the vet Andy. Think I’d be put down.

Gary Abbott

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Re: DIY cams
« Reply #6 on: May 26, 2020, 09:14:03 AM »
Hi,

Yep Dyno run was good.  Still some work to do but getting there.  Hopefully get some track time soon.

distracted at the moment with decorating duties, hope to get back to cam measurement bench later in week.

Regards Gary.