| Author | Message | ||
     Tpdworks |
Is there any current experience with the Hildstrom rotor mod? I like the simplicity and the DIY aspect of drilling larger air cooling holes in the rotor rather than drilling the tiny oil passage and risking lubrication issues. That being said I would like as long term a fix as possible while I'm this deep into the CR charging system. As of '16 there were a handful of 1125's out there with the hildstrom mod, any of you guys still running? EBR or Hildstrom? | ||
| Terrys1980 |
The Hildstrom should be high speed balanced once drilled but should offer better oil flow and cooling. People have DIY the oil passage as well but it takes some patience and precision. | ||
| Nuts4mc |
Hildstrom method -you would need to find a shop that can do "dynamic" (rotational) balancing...possibly someone that does propellers for boats/ships/planes...a long time ago I was in charge of a balancing department (fans for Aerospace applications) we used "Gisholt" balancers...Garrett Air Research in L.A.( Turbo chargers for diesel trucks) was a big user of Gisholt machines...if you choose a shop to modify the rotor via Hilstrom method...you might just find a "balancing" shop to do both the machining and balancing... http://www.hitekbalancing.com/dynamic-balancing-se rvices-in/Portland/Oregon/ you need to "balance" (sorry for the pun)the cost between the Hilstrom method and the EDM method...you may find there are a lot more shops equipped with EDM machines than dynamic balancers thus... the EDM method may be lower cost. hth | ||
| Tpdworks |
Okay, so either way is a valid method? I have a rotary indexer and a Bridgeport mill. I can indicate everything in and machine the Hildstrom holes with extreme accuracy. I'm wondering if I'd still need balancing... hmm. | ||
| Tpdworks |
I really want to get this right, because I don't have the stomach for Dhays1775 CR surgury.   (Message edited by TPDworks on September 17, 2018) | ||
| Nuts4mc |
I believe Rotax/BMW twins used the "Hildstrom" method to cure their overheating stator issues...sounds like you're an accomplished machinist...do your best to "repeat" hole size and location and it may work out for you...the Gisholt machines work on vibration measurement and when operating one, small changes to the rotating mass resulted in the best results ( it takes time /experience to efficiently run a Gisholt balancer)...rehearse your set up and operation before you start making chips...best of luck! | ||
| Stimbrell |
One is a proven fix from the company that designed and built the vehicle, the other is not. Make your decision based on that. | ||
| Tpdworks |
I have seen the BMW comparison photo, they did fix it by opening up airflow. They also went to a forged rotor rather than billet, I'm guessing they used something like a Gisholt machine after production. Thanks for chiming in with that, I didn't consider the balance component or vibration analysis. I know the EBR fix is an OEM method, but rumor has it that people have put some significant mileage on the Hildstrom fix. I'll post my decision and results when whatever mod I do is complete. Please free to comment with any other thoughts. Happy riding! | ||
| Panshovevo |
Since you have a Bridgeport, can I make a suggestion? I would like to see the results of a test like Hildstrom ran on his stator, only this time comparing the cooling efficiency of straight bored holes compared to steeply angled holes. A local boat builder hired a friend of mine as a machinist. I was shooting the bull with the guy one day, and he told me he was making through hull fittings for engine cooling, and they were trying to minimize the size and drag of the water pickups while still getting sufficient water flow for cooling. I suggested he try boring the pickup screen holes at an angle, and flattening the pickup plate to reduce the drag. I ran in to him about six months later, and he was dressed to the nines, and strutting around like he was king of the world. I asked him what was up. He told me he had come up with a new way of making the water pickups for through hull fittings that was way more efficient and he had gotten a promotion and a big raise that week because of it. I asked him if he had bored the holes at an angle. He gave me a funny look and asked who had told me about it. It was supposed to be a company secret! I reminded him that I had suggested it to him the last time I saw him. His wife and a few friends were around, and he called me a damn liar and insisted on knowing who had leaked the info to me. I called over the mutual friend who had been present at the earlier meeting where I had made the suggestion, and asked if he remembered the conversation. He hemmed and hawed around, and gave me a non-answer. Later, he told me he remembered it just fine, but didn’t want to embarrass the guy in front of his wife and friends. I told him I’d go along with it as long as he promised to straighten the guy out privately. He did. The guy never spoke to me again. Didn’t bother me a bit. | ||
| Tpdworks |
I was also considering this! Mill the holes off of center to create an ability to scoop air as the rotor turns. I wont be doing a thermalcouple or anything fancy to get cooling results. Another strategy I'm considering is placing large countetsinks on the outside of the rotor for every hole drilled, that way I can reduce amount of material in the hole and also direct more air through during rotation. | ||
| Nuts4mc |
I believe what Pan is suggesting is tilt the spindle of the mill so that the cooling holes are produced at an angle that would act like scoops as described in his marine engine cooling post...kinda like small NACA vents on stock cars...you would have to pay attention to rotation of the rotor in order to get the angle correct...and rotate the rotary table while machining the holes...kinda tricky to repeat exactly on each scoop....if you decide to use straight holes with a countersink....remember that sharp corners or edges can produce cracks...a small radiused edge would be best...hth | ||
| Dannybuell |
Great Thread !! | ||
| Tpdworks |
Nuts4mc, I think I would achieve the same results by drilling off center rather than tilting the head on the mill. However, I'm getting ready for the machine work and I think what I will do instead is run a countersink into strait holes to reduce the side wall of the drilled holes and funnel more air around. | ||
| Nuts4mc |
Sounds like you're ready to make some chips! Suggestions: a) clean off the magnets with some alcohol or solvent (acetone) and mask off the magnets with some old fashioned masking tape...the tape may prevent little piece of metal from being attracted to the magnets and sticking in any nooks or crannys. b) there are many "angles" of c'sinks...82 deg (US) and 90 deg (Eur), 100 deg, 60 deg...pick one and don't mix em up on the work piece. c) I had better luck ( less chatter) with the "Weldon" style C'sink than I did with the ones that look like a reamer or end mill...you may want to try C'sinking a piece of stock and see which one gives you the best finish. d) you may want to use a Flat head screw ( non magnetic - Brass, SS) for a "gauge" to inspect you depth of c'sink e) be careful when clamping the work piece to the rotary table...too much force could damage (crack) the magnets. f) remember to de-burr your work...AND remove the tape before you start the reassembly process. Happy machining! - hth (Message edited by nuts4mc on October 04, 2018) | ||
| Panshovevo |
Tpdworks, what do you mean by “drilling the holes offcenter”? I can’t seem to picture what you mean by that. As far as countersinking the holes to increase the airflow, my gut feeling is that you would be better off drilling a larger hole than countersinking a smaller hole. Breaking the sharp edges of the holes would be a good idea, and could be done with the right countersink, with care to remove the same amount of material from each hole. | ||
| Pwillikers |
Sort of like this:  (Message edited by pwillikers on January 24, 2019) | ||
| Ceejay |
Reviving an old thread - how’d this turn out? | ||
| Wombat |
Anyone have any updated feedback on the Hildstrom rotor cooling method…is it working? |
