Electric Starter System for Model Engines

[petertha]

The typical RC starters use variations of a heavier gage copper bar bent at a shape so that when the rubber cover 'trigger' is squeezed it makes contact. For reference the Sullivan specs are: S601 – Deluxe Hi-Tork Starter 12 Volts with a maximum of 80 Amps. 210 in-oz of torque. 5500 no load RPM. For all engines up to .60 cubic inches and most to 1.20 cubic inches. It also includes an aluminum pulley grove drive cone. You can find these used for near giveaway prices as RC are migrating from nitro to electrics or out of RC altogether. BTW the groove in the pulley has been used for a belt system on heli's & boats & cars for eons.

The 4:1 planetary gear starter I recently bought runs on 4S lipo (14.4v). I can't recall the current I measured but I want to say ~5A static. As received the trigger was not turning off reliably, so I opened it up. Appears to be the same copper bar concept. Once I adjusted the bend / action it performed correctly now.

 

[Brian Rupnow]

Ouch--Ouch---Ouch!!! Just got my timing belt pulleys and belt from McMaster-Carr. They look great but cost $156.00. And, folks,--that is outrageous. I will be taking measurements from the pulleys and seeing what's involved in machining my own pulleys in future. The belts I will buy but I'm sure that I can machine my own pulleys from a piece of aluminum round stock for about 1/5 of the cost. My labour is free---to me anyways.---Brian

 

[Gedeon Spilett]

Is this gizmo strong enough to meet your needs?
https://www.stirlingkit.com/collect...g-portable-tool-for-musa-retrol-engine-models

 

[Steamchick]

Brian. Be sure to get the tension right. Too tight or too slack means death to the belt. Factory setting of machines is very accurate (usss sound on a known span at the correct tension from a calibration machine). Within 1%. NON-factory setting is usually wildly inaccurate and damages belt maker's reputations, and users wallets.
Enjoy. K2

 

[Brian Rupnow]

Zephyrin-I don't really know. Andrew Whale out of the UK designed something very similar to what I am building and I more or less copied his idea. I wanted to have the ability to have both hands free while the engine was being turned over.---Brian

 

[Steamchick]

A modeller friend gets electric motors, Gearboxes, starter centrifugal clutches, batteries, etc. from "model racing cars" as he has a shop nearby.... and a good relationship with the shop owner! All his 1 ~10cc engines have dedicated starters built into the wood platforms beneath the model he is displaying. I think they are all started using a tiny timing belt from below... to the end of the crankshaft? - The ignition all hides below the wood base as well. Just an ON-OFF switch, ON light (LED) and push button (Starter) show on the surface of the wood base.
K2

The horizontally opposed Ricardo 2-stroke engine on the right has switches and buttons hidden at the back of the wood base.

The Switch, light and button are at the Left hand side (hidden from view) of the wood base on the 3-cylinder water-cooled side valve 4-stroke on the left, and similarly at the back of the horizontal 4 stroke on the right.

All 6 models by the same guy. He sets the standard for modelling and presentation in our club.
"Enjoy"
K2

 

[Brian Rupnow]

Steamchick--that is pretty well exactly the same as I am attempting to do here. My starting rig is more generic and will eventually fit all of my models engines, but the cost is too high to have every engine with a dedicated starter system.---Brian

 

[Steamchick]

Hi Brian: It can be a lot cheaper I reckon. Have you considered Vee-pulleys and O-ring for a belt drive? I bought some timing belts and pulleys from Radio Spares (RS in the UK._). £25 a few years ago... NOT $160... ! But make my own Vee-pulleys and use O-rings for belts to drive a lathe with a 150W motor....
My friend by parts for Model Cars for a few £ a part I understand. He does not have £120 for 2 pulleys and a belt.
We live and learn from each other.
K2

 

[davidyat]

Brian, have you ever tried other avenues to purchase items? I do a LOT of purchasing on eBay. I find an item in the US only with free shipping. I can also check the sellers' profile. If a seller has sold thousands of items with a 99% approval rating, I would trust them. I saw these items on eBay:
https://www.ebay.com/itm/3341330941...ybBtOEVSwvQP4KrY9mWQwItIaT|tkp:Bk9SR_jX8OL5Yg
https://www.ebay.com/itm/2231008451...B1j%2BwDm%2FQw%3D%3D|ampid:PL_CLK|clp:3458402
Granted it's only one item from this seller. I do a lot of digging until I get what I want. It does work for me, don't know if you're receptive to this kind of purchasing. For me it does save me a lot of money. It's your choice.
Grasshopper

 

[Brian Rupnow]

davidyat--I think of Ebay, sometimes I look on the Ebay website, but I'm very shy about using it. I don't very often make expensive purchases, but when I do I prefer to deal with a company that I know is reputable. Sometimes this costs me money---more money than I like to spend. Fortunately, I don't build very much stuff that has expensive components.---Steamchick--o-rings are not strong enough to transfer the torque required to start one of my engines, and they stretch terribly. V-belts require a great deal of tension to transfer torque, and my engines don't really like having a lot of tension on the crankshaft bearings. A timing belt with teeth gives a positive drive same as a roller chain and sprockets, and while they require some tightness, it is very little compared to a v-belt.---Brian

 

[Vietti]

Agree with Grasshopper.

The prices you had to pay for pulleys and belts are outrageous! I have used quite a few G2 pulleys and belts. I don't know how things work getting stuff from overseas but can you take a look at Temu, aliexpress, and other Chinese suppliers? Ebay is a good source as mentioned. Even Amazon has belts and pulleys at good prices.

John

 

[oldengineguy]

I have made adaptors for some of my engines to put in a "one way" bearing on the crank. A shaft of the right dimension and a cheap cordless drill will spin over any thing I've got including a 5 cyl Kinner. Can't see the point of belts and pulleys.
Colin

 

[Vietti]

I like the ability esp. at a show to push a button and start the engines, without jumping up and fumbling around with a drill. Done well the starter adds realism and interest to the model IMHO.
Each to their own.

 

[Brian Rupnow]

That price was part of the joy of being Canadian. Right now, a dollar of my money is worth 79 cents of your money. Then add on the shipping. I'm a little horrified by the cost of anything out of the USA right now, but if you want to play, you have to pay.

 

[bluejets]

Ouch--Ouch---Ouch!!! Just got my timing belt pulleys and belt from McMaster-Carr. They look great but cost $156.00.

Dare I say, without being too outlandish, more money than sense.
I've used synchronous pulleys and belts from China with zero complaints.
Cost of two pulleys and belt fot the new starter for the boat was around AUD$30 including delivery.

 

[ajoeiam]

Y

That price was part of the joy of being Canadian. Right now, a dollar of my money is worth 79 cents of your money. Then add on the shipping. I'm a little horrified by the cost of anything out of the USA right now, but if you want to play, you have to pay.

You might want to check your exchange rate mr Brian - - - - I think you'll find it between 0.72 and 0.73 about now.

I don't mind paying the exchange but the added fees because its crossed a border are outrageous and then shipping cross border isn't even that good.
For example - - abebooks - - - shipping withing usa one book was $6 and the other under $7 - - - - to canuckistan - - - one was $35 and the other $65 (usd).
That's not even in the same ball park - - - I'm being ripped off!

 

[Steamchick]

Hi Brian. I appreciate the belt tension difference between Vee-belt arrangements and toothed belt arrangements. The principle of pre-tension in both is effectively the same - though at different values. Yes, the toothed belt has the teeth to transmit torque, but a substantial torque transmission also comes from the friction of the flat portion of the belt upon the OD of the toothed pulley. The majority of tension is when the starter is operating, not pre-tension. With Vee-pulleys, the belt does a lot of work (= heat and "wasted" power) engaging the belt in the vee - and pulling it in tight under the tensile load of whatever is being drive. Then again the belt has to be "pulled-out" of the vee in which it has been wedged.... the residual (initial) tension is just a level to ensure it does not slip as the load in engaged, and not "full tension" from when it is driving. So on a properly designed system - I.E. factory components you can buy - the pre-tension is a relatively small fraction of the tension when the belt is transmitting power. The worst case is when the starter is just pulling the belt for the first compression of the engine, and speed is low, possibly friction high, and lubrication just being generated inside the sliding surfaces.. (I think?? - You will correct me if I am wrong, I am sure!). Once it has cranked a couple of times the engine will naturally free itself (lubrication where it should be) and the initial belt load reduced. If running a free-wheel between the starter motor and crankshaft, the belt only needs to be running for a short time during starting. The pre-tension of the belt should only be a small fraction of belt-loading on bearings when the starter motor is driving the engine.
That said, the pre-load for Vee-belts is generally higher than on toothed belts, but not much higher. - Unless the design isn't very good... as efficiency drops at higher tensions.
But I never worked professionally with belt drives, just next to the engineer that did, so may be completely wrong.... ? - And that was 40 years ago...
K2

 

[Tidza]

A website that I looked at (can't remember which) sold a jockey wheel and spring to keep the tension correct on the non drive side of the toothed belt.

 

[L98fiero]

Dare I say, without being too outlandish, more money than sense.
I've used synchronous pulleys and belts from China with zero complaints.
Cost of two pulleys and belt fot the new starter for the boat was around AUD$30 including delivery.

Agreed, I have too and for infrequent and uncritical applications like starting a miniature engine, it doesn't take much of a belt and pulley.

 

[Brian Rupnow]

So, today the project started. I picked up my material this morning, cut everything to "On size plus 1/16" on my bandsaw and decided that the travelling plate which supported the drill motor had the most work in it, so I started with it. It is 3/4" thick. The cut out was done with 0.8" plunge cuts every 0.100" using a 1/2" endmill. Thats 140 plunge cuts--my right arm may fall off, but the hole is cut to size. Tomorrow while it's still up on the mill I will drill and tap whatever holes are required and put the two 1/2" long holes in it for the guide rods.